Communicable Diseases Book by MR Daniel Karani

LECTURE NOTES
For Nursing Students
Communicable Disease
Control
Mulugeta Alemayehu
Hawassa University
In collaboration with the Ethiopia Public Health Training Initiative, The Carter Center,
the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education
2004
Funded under USAID Cooperative Agreement No. 663-A-00-00-0358-00.
Produced in collaboration with the Ethiopia Public Health Training Initiative, The Carter
Center, the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education.
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Limited permission is granted free of charge to print or photocopy all pages of this
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©2004 by Mulugeta Alemayehu
All rights reserved. Except as expressly provided above, no part of this publication may
be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, recording, or by any information storage and retrieval system,
without written permission of the author or authors.
This material is intended for educational use only by practicing health care workers or
students and faculty in a health care field.
Communicable Disease Control
Preface
This lecture note was written because there is currently no

uniformity in the syllabus and, for this course additionally,
available textbooks and reference materials for health
students are scarce at this level and the depth of coverage in
the area of communicable diseases and control in the higher
learning health institutions in Ethiopia. The author hopes that
the material will, to some extent, solve this problem. Although,
this lecture note is prepared and intended for use primarily for
nursing students, other health science students and health
professionals can use it. After using this material, students are
expected to be able to:
describe the epidemiology and scope of communicable
diseases in Ethiopia and factors involved in the
transmission of communicable diseases;
identify the preventive and control measures of each of
the communicable diseases;
play an active role in the prevention and control of
communicable diseases;
organize and implement effective health education on
communicable diseases, and;
participate in teaching junior staff and significant others in
health courses on managing patients with communicable
diseases.
i
In order to accomplish the above objectives, efforts have been

made to address all the topics mentioned in the
communicable disease outline of nursing students, including:
epidemiology of communicable diseases in Ethiopia; definition
and descriptions of the transmission, prevention and control of
communicable diseases, air-borne diseases, vector-borne
diseases, sexually-transmitted diseases, zoonotic diseases,
and food-borne diseases (food poisoning and infection). The
last chapter has a brief description of nursing principles in the
management of communicable diseases.
Specific learning objectives and review questions have been

set for each chapter. Moreover, each disease has been
discussed in terms of its definition, infectious agent,
epidemiology, clinical manifestation, diagnostic criteria,
treatment, nursing care (for some diseases) and prevention
and control methods. Important words or phrases in the text
have been defined in the glossary. References used have
been also listed at the end.
ii
Acknowledgments
I am highly indebted to acknowledge The Carter Center -

Ethiopia Public Health Training Initiative (EPHTI), Addis
Ababa, for its magnificent contribution in the preparation of
this useful lecture note in terms of logistics and administrative
support. I am also indebted to my students, to whom I owe
much of what I have learned about teaching the
communicable disease control course, and whose interest
and participation have sustained my motivation during the
arduous writing of this material.
I would like to express my deep appreciation to Dr. Tadesse

Anteneh for his advice, encouragement, and support in the
preparation of this lecture note.
My deep appreciation also goes to Ato Keneni Gutema, Ato

Arega Awoke and S/r Addisalem Yilma, for their constructive
comments and suggestions on an earlier draft and for taking
time out from their busy schedules to read it.
I would like to acknowledge Ato Abraham Alano and Ato

Yared Kifle, who reviewed the final draft and gave me
invaluable comments and suggestions.
Last but not least my thanks also go to W/t Yiftusra Abebe

and W/t Tigist Ayele who have assisted me in accomplishing
all of the secretarial work of this text.
iii
Table of Contents
Preface i
Acknowledgement iii
Table of Contents iv
List of Figures ix
Abbreviations and Acronyms x
CHAPTER ONE: INTRODUCTION 1

1.1 Learning Objectives 1
1.2 Epidemiology and Scope of Communicable 2
Diseases in Ethiopia
1.3 Epidemiological Terms and Definitions 4
Review Questions 7
CHAPTER TWO: DEFINITIONS, DESCRIPTIONS 8

OF THE TRANSMISSION, PREVENTION AND
CONTROL OF COMMUNICABLE DISEASES

2.2 Communicable Diseases 8
2.3 Chain of Disease Transmission 9
2.4 Carrier and Its Types 15
2.5 Time Course of Infectious Diseases 15
2.6 Levels of Prevention 16
2.7 Communicable Disease Control 19
Review Questions 22
iv
CHAPTER THREE: ORAL-FECAL TRANSMITTED 23

DISEASES
3.2 Introduction 23
3.3 Feces Mainly in Water 24
3.4 Feces Mainly in Soil 42
3.5 Direct Contact With Feces 56
Review Questions 61
CHAPTER FOUR: AIR-BORNE DISEASES 62

4.2 Introduction 62
4.3 Common Cold 63
4.4 Measles 65
4.5 Influenza 68
4.6 Diphtheria 70
4.7 Pertusis 73
4.8 Pneumococcal Pneumonia 76
4.9 Meningococcal Meningitis 79
4.10 Tuberculosis 81
4.11 Leprosy 87
Review Questions 91
CHAPTER FIVE: ARTHROPOD OR 92

INTERMEDIATE VECTOR-BORNE DISEASES
v
5.2 Introduction 92
5.3 Mosquito-borne Diseases 93
5.4 Flea-borne Diseases 106
5.5 Louse-borne Diseases 111
5.6 Snail-borne Diseases 116
Review Questions 126
CHAPTER SIX: SEXUALLY TRANSMITTED 122

DISEASES
6.2 Introduction 127
6.3 Syphilis 129
6.4 Chancroid 133
6.5 Lymphogranuloma Venereum 135
6.6 Herpes Genitalia 137
6.7 Candidiasis 139
6.8 Gonorrhea 141
6.9 Trichomoniasis 143
6.10 HIV/AIDS 146
CHAPTER SEVEN: ZOONOTIC DISEASES 151

7.3 Food of Animals 152
7.4 Animal Bite Diseases 169
vi
7.5 Direct Contact Diseases 172

7.6 Animal Reservoir Diseases 177
CHAPTER EIGHT: FOOD-BORNE DISEASES 188

8.3 Staphylococcal Food Poisoning 189
8.4 Botulism 192
8.5 Salmonellosis 195
CHAPTER NINE: NURSING RESPONSIBILITIES IN 199

THE MANAGEMENT OF COMMUNICABLE
DISEASES
Glossary 206
References 211
vii
List of Figures
Fig. 3.1 The five “Fs” which play an important role in 24

fecal-oral diseases transmission
Fig. 3.2 Transmission and life cycle of Entameoba 33
histolytica
Fig. 3.3 Transmission and life cycle of Giardia lamblia 36
Fig. 3.4 Transmission and life cycle of Ascaris 44
lumbricoids
Fig. 3.5 Transmission and life cycle of Trichuris 47
trichuria
Fig. 3.6 Transmission and life cycle of Entrobius 50
Vemicularis
Fig. 3.7 Transmission and life cycle of Strongyloides 52
Stercolaris
Fig. 3.8 Transmission and life cycle of Hookworms 54
Fig. 5.1 Transmission and life cycle of Malaria 96
parasites
Fig. 5.2 Transmission and life cycle of W. bancrofti 100
and Brugia species
Fig. 5.3 Transmission and life cycle of Schistosoma 119
species
Fig. 7.1 Transmission and life cycle of Taenia solium 154
and Taenia saginata
Fig. 7.2 Transmission and life cycle of Leishmania 179
parasites
Fig. 7.3 Transmission and life cycle of T.b. 183
rhodesiense and T.b. gambiense
viii
Abbreviations and Acronyms
AFB Acid Fast Bacilli

AIDS Acquired Immuno-Deficiency Syndrome
BCG Bacillus of Calmate-Guirein
Bid Bies in dies (two times a day)
B. Sc. Bachelor of Science degree
0
C Degree Celsius
CNS Central Nervous System
CSF Cerebro-spinal fluid
CT Computerized Tomography
DEC Diethylcarbamazin Citrate
DOTS Directly Observed Treatment Short course
GIT Gastro-intestinal Tract
HIV Human Immuno-deficiency Virus
IgM Immunogloblin M.
IM Intramuscular
IU International Unit
IV Intravenous
Kg Kilogram
MOH Ministry of Health
MRI Magnetic Resonance Imaging
OPV Oral Polio Vaccine
PO Per os (per mouth)
+
PTB Smear Positive Pulmonary Tuberculosis
QID Quadris in dies (four times a day)
ix
STD Sexually Transmitted Disease

STI Sexually Transmitted Illness
TB Tuberculosis
Tid Tries in dies (three times a day)
URTI Upper Respiratory Tract Infection
USA United States of America
WHO World Health Organization
x
CHAPTER ONE
INTRODUCTION
1.1 Learning Objectives
At the end of this chapter, the student will be able to:
- Describe the burden of communicable diseases in
Ethiopia.
- Define epidemiology and epidemiological terminologies.
- Identify the major communicable diseases that pose
health problems in Ethiopia.
Diseases can be classified according to two major

dimensions, namely the time course and cause. According to
the time course, they are further classified as acute
(characterized by a rapid onset and a short duration), and
chronic disease (characterized by prolonged duration).
Based on the cause, diseases can be broadly categorized as

infectious, (i.e. caused by living parasitic organisms such as
viruses, bacteria, parasitic worms, insects, etc.), or as non-
infectious (which are caused by something other than a living
parasitic organism).
However, most of the common diseases in Africa are

environmental diseases (infectious) due to infection by living
1
organisms. These are called communicable diseases,

because they spread from person to person, or sometimes
from animals to people. They occur at all ages but are most
serious in childhood and they are to a great extent
preventable. In developed countries where they have been
prevented, other health conditions such as accidents and
degenerative diseases become the most common. Therefore,
communicable diseases remain very important in developing
countries because:
Many of them are very common
Some of them are serious and cause death and disability
Some of them cause widespread out breaks of disease or
epidemics
Most of them are preventable by fairly simple means.
Poor socio-economic status of the individuals makes them
vulnerable to a variety of diseases
Low educational status
Lack of access to modern health care service
1.2 Epidemiology and Scope of Communicable

Diseases in Ethiopia
During the past 70 years, there has been a dramatic fall in the
incidence of infectious diseases, particularly in developed
countries. This is due to severeal factors including:
Immunization
2
Anti-microbial chemotherapy
Improved nutrition
Better sanitation and housing
In less developed countries, however, especially in the

tropics, infectious diseases continue to be one of the
commonest causes of death, particularly in children. Ethiopia,
as part of the developing world, has two big health problems.
These are:
Infectious diseases (communicable diseases) 80% of
these can be prevented by simple sanitary measures.
Nutritional problems
The magnitude of infectious diseases in Ethiopia can be seen
from the 1993 E.C. MOH report. Accordingly:
The top leading causes of outpatient visits were:
- All types of malaria (10.4%)
- Helminthiasis (6.7%)
- Acute upper respiratory infection (6.5%)
- Bronchopneumonia (5.5%)
- Infections of skin and subcutaneous tissue (4.6%)
- Dysentery (3.5%)
- Tuberculosis of respiratory system (2.2%)
- Sexually transmitted infection (2.2%)
- Bronchitis, chronic and unqualified (1.9%)
The top leading causes of admission were:
3
- Pneumonia (8.9%)
- Tuberculosis of respiratory system (7.8%)
- Bacillary dysentery (1.6%)
- Gastroenteritis and colitis (1.5%)
- Meningitis (0.9%)
The top leading causes of deaths were:
- Tuberculosis of the respiratory system (10.1%)
- Pneumonia (7.3%)
- Bacillary dysentery (2.2%)
- Meningitis (1.5%)
- Gastroenteritis and colitis (1.1%)
- AIDS (0.8%)
- Leishmaniasis (0.5%)
Others, like yellow fever, acute febrile illnesses, trachoma

(commonest cause of blindness in Ethiopia), and
trypanosomiasis, are the major public health problems in our
country.
1.3 Epidemiological Terms and Definitions
Epidemiology- the study of the frequency, distribution and

determinants of disease and other health related conditions in
human populations, and the application of this study to the
4
promotion of health and to the prevention and control of health

problems.
Some of the components in the definition of epidemiology are:
"Populations” Epidemiology focuses on the effects of
disease on populations
"Disease and health related conditions” Epidemiology
indicates that everything around us and everything we do
affects our health.
"Frequency" shows that “epidemiology” is a quantitative
science (e.g. occurrence of illness is measured using
morbidity rates).
"Distribution" refers to the occurrence of disease by
place, person and time.
"Determinants” These are factors that determine
whether or not a person will get a disease.
The causes of diseases are classified epidemiologically

as:
Primary causes - Factors that are necessary for a disease to
occur, and in whose absence the disease will not occur (e.g.
infectious agents, vitamin deficiencies).
1. Contributing, predisposing, or aggravating factors -
Risk factors whose presence is associated with an
increased probability that disease will occur/develop
later(e.g. Poverty is the most powerful environmental
determinant in the disease occurrence, Habit of cigarette
5
smoking leads to lung cancer. Having multiple sexual

partners results in STI).
Definition of other epidemiological terms:

1. Epidemics - the occurrence of any health related
condition in a given population in excess of the usual
frequency in that population.
2. Endemic - a disease that is usually present in a
population or in an area at a more or less stable level.
3. Sporadic - a disease that does not occur in that
population, except at occasional and irregular intervals.
4. Pandemic - an epidemic disease which occurs world-
wide
5. Disease - a state of physiological or psychological
dysfunction.
6. Infection - the entry and development or multiplication of
an infectious agent in the body of man or animal
7. Contamination – presence of living infectious agent upon
articles
8. Infestation – presence of living infectious agent on the
exterior surface of the body
9. Infectious - caused by microbes and can be transmitted
to other persons.
10. Infectious agent- an agent capable of causing infection
6
Review Questions
1. How do you compare the impact of communicable

disease in Ethiopia with that of the developed world?
2. What are some of communicable diseases that create
major health problems in Ethiopia?
3. Define the following terms:
- Epidemiology
- Epidemics
- Endemic
- Pandemic
- Sporadic
- Infection and infectious agent
4. Why are communicable diseases very important in
Ethiopia?
7
CHAPTER TWO
DEFINITION, DESCRIPTION OF THE

TRANSMISSION, PREVENTION AND
CONTROL OF COMMUNICABLE
DISEASES
At the end of this chapter the student will be able to:

- Define communicable disease.
- Describe the factors involved in the chain of
communicable disease transmission.
- Identify the different levels of disease prevention.
- Apply the different control methods of communicable
diseases.
2.2 Communicable Diseases
These are illnesses due to specific infectious agents or its

toxic products, which arise through transmission of that agent,
or its toxic products from an infected person, animal or
inanimate reservoir to a susceptible host, either directly or
8
indirectly, through an intermediate plant or animal host, vector

or inanimate environment.
2.3 Chain of Disease Transmission
This refers to a logical sequence of factors or links of a chain

that are essential to the development of the infectious agent
and propagation of disease. The six factors involved in the
chain of disease transmission are:
a. Infectious agent (etiology or causative agent)
b. Reservoir
c. Portal of exit
d. Mode of transmission
e. Portal of entry
f. Susceptible host
a. Infectious agent: An organism that is capable of

producing infection or infectious disease.
On the basis of their size, etiological agents are generally
classified into:
Metazoa (multicellular organisms). (e.g. Helminths).
Protozoa (Unicellular organisms) (e.g. Ameobae)
Bacteria (e.g. Treponema pallidum, Mycobacterium
tuberculosis, etc.)
Fungus (e.g. Candida albicans)
Virus (e.g. Chickenpox, polio, etc.)
9
b. Reservoir of infection: Any person, animal, arthropod,

plant, soil or substance (or combination of these) in which an
infectious agent normally lives and multiplies, on which it
depends primarily for survival and where it reproduces itself in
such a manner that it can be transmitted to a susceptible host.
Types of reservoirs
1. Man: There are a number of important pathogens that are
specifically adapted to man, such as: measles, smallpox,
typhoid, meningococcal meningitis, gonorrhea and syphilis.
The cycle of transmission is from human to human.
2. Animals: Some infective agents that affect man have their

reservoir in animals. The term “zoonosis” is applied to disease
transmission from animals to man under natural conditions.
For example:
Bovine tuberculosis - cow to man
Brucellosis - Cows, pigs and goats to man
Anthrax - Cattle, sheep, goats, horses to man
Rabies - Dogs, foxes and other wild animals to man
Man is not an essential part (usual reservoir) of the life
cycle of the agent.
Animal …….. Animal…………Animal
↓
Human
10
3. Non-living things as reservoir: Many of the agents are

basically saprophytes living in soil and fully adapted to live
freely in nature. Biologically, they are usually equipped to
withstand marked environmental changes in temperature and
humidity.
E.g. Clostridium botulinum etiologic agent of Botulism
Clostridium tetani etiologic agent of Tetanus
Clostridium welchi etiologic agent of gas gangrene
c. Portal of exit (mode of escape from the reservoir): This

is the site through which the agent escapes from the
reservoir. Examples include:
GIT: typhoid fever, bacillary dysentery, amoebic
dysentery, cholera, ascariasis, etc.
Respiratory: tuberculosis, common cold, etc.
Skin and mucus membranes: Syphilis
d. Mode of transmission (mechanism of transmission of

infection): Refers to the mechanisms by which an infectious
agent is transferred from one person to another or from a
reservoir to a new host. Transmission may be direct or
indirect.
1. Direct transmission: Consists of essentially immediate

transfer of infectious agents from an infected host or reservoir
to an appropriate portal of entry. This could be:
11
a. Direct Vertical
Such as: transplacental transmission of syphilis, HIV, etc.
b. Direct horizontal
Direct touching, biting, kissing, sexual intercourse, droplet
spread onto the conjunctiva or onto mucus membrane of
eye, nose or mouth during sneezing coughing, spitting or
talking; Usually limited to a distance of about one meter or
less.
2. Indirect transmission
a. Vehicle-borne transmission: Indirect contact through
contaminated inanimate objects (fomites) like:
Bedding, toys, handkerchiefs, soiled clothes, cooking or
eating utensils, surgical instruments.
Contaminated food and water
Biological products like blood, serum, plasma or IV-fluids
or any substance serving as intermediate means by which
an infectious agent is transported and introduced into a
susceptible host through a suitable portal of entry. The
agent may or may not multiply or develop in the vehicle
before it is introduced into man.
b. Vector-borne transmission: Occurs when the infectious

agent is conveyed by an arthropod (insect) to a susceptible
host.
12
1. Mechanical transmission: The arthropod transports the

agent by soiling its feet or proboscis, in which case
multiplication of the agent in the vector does not occur. (e.g.
common house fly.)
2. Biological transmission: This is when the agent multiplies

in the arthropod before it is transmitted, such as the
transmission of malaria by mosquito.
C. Air-borne transmission: Dissemination of microbial agent

by air to a suitable portal of entry, usually the respiratory tract.
Two types of particles are implicated in this kind of spread:
dusts and droplet nuclei.
Dust: small infectious particles of widely varying size that

may arise from soil, clothes, bedding or contaminated floors
and be resuspended by air currents.
Droplet nuclei : Small residues resulting from evaporation of
fluid (droplets emitted by an infected host). They usually
remain suspended in the air for long periods of time.
e. Portal of entry: The site in which the infectious agent

enters to the susceptible host. For example:
Mucus membrane
Skin
Respiratory tract
13
GIT
Blood
f. Susceptible host (host factors): A person or animal

lacking sufficient resistance to a particular pathogenic agent to
prevent disease if or when exposed. Occurrence of infection
and its outcome are in part determined by host factors. The
term “immunity” is used to describe the ability of the host to
resist infection.
Resistance to infection is determined by non-specific and

specific factors:
Non-specific factors
Skin and mucus membrane
Mucus, tears, gastric secretion
Reflex responses such as coughing and sneezing.
Specific factors
Genetic-hemoglobin resistant to Plasmodium falciparum
Naturally acquired or artificially induced immunity. Acquired
immunity may be active or passive.
Active immunity- acquired following actual infection or

immunization.
Passive immunity- pre-formed antibodies given to the host.
14
2.4 Carrier and Its Type
A carrier is an infected person or animal who does not have

apparent clinical disease but is a potential source of infection
to others.
a. Healthy or asymptomatic carriers: These are persons
whose infection remains unapparent. For example, in
poliovirus, meningococcus and hepatitis virus infections,
there is a high carrier rate.
b. Incubatory or precocious carriers: These are individuals
or persons who excrete the pathogen during the
incubation period (i.e. before the onset of symptoms or
before the characteristic features of the disease are
manifested).
E.g. Measles, mumps, chickenpox and hepatitis.
c. Convalescent Carriers: These are those who continue to
harbor the infective agent after recovering from the
illness. E.g. Diphtheria, Hepatitis B virus.
d. Chronic Carriers: The carrier state persists for a long

period of time. E.g. Typhoid fever, Hepatitis B virus infection
2.5 Time Course of Infectious Diseases
Incubation period: It is the interval of time between infection

of the host and the first appearance of symptoms and signs of
the disease.
15
Prodormal period: It is the interval between the onset of

symptoms of an infectious disease and the appearance of
characteristic manifestations. For example, in a measles
patient, fever and coryza occur in the first three days and
Koplick spots in the buccal mucosa and characteristics skin
lesions appear on the fourth day.
Period of communicability: The period during which that

particular communicable disease (infectious agent) is
transmitted from the infected person to the susceptible host.
2.6 Levels of Prevention
The different points in the progression of a disease at which

one can intervene can be classified according to three levels
of prevention: primary, secondary, and tertiary.
a. Primary prevention: The objectives here are to promote

health, prevent exposure, and prevent disease.
Health promotion: This consists of general non-specific

interventions that enhance health and the body’s ability to
resist disease, such as measures aimed at the improvement
of socio-economic status through the provision of adequately-
paid jobs, education and vocational training, affordable and
adequate housing, clothing, and food, old-age pension
benefits; emotional and social support, relief of stress, etc. In
16
short it is any intervention that promotes a healthier and

happier life.
Prevention of exposure:- This includes actions such as the

provision of safe and adequate water, proper excreta
disposal, vector control, safe environment at home (e.g.,
proper storage of insecticides and medicines, out of children’s
reach), at school and at work (e.g., proper ventilation,
monitoring of harmful substances in factories), and on the
streets (e.g., driver licensing laws).
Prevention of disease:-This occurs during the latency period

between exposure and the biological onset of disease. An
example for this is immunization.
Immunization against an infectious organism does not prevent

it from invading the immunized host, but prevents it from
establishing an infection. Active immunization means
exposing the host to a specific antigen against which it will
manufacture its own protective antibodies after an interval of
about three weeks (during which the immunized person
remains susceptible to the disease). Passive immunization
means providing the host with the antibodies necessary to
fight against disease. Both forms of immunization act after
exposure. However, for active immunization to be protective,
the timing of its administration must be at least three weeks
prior to exposure. Passive immunization, on the other hand,
17
is commonly given after exposure has occurred (as in the

case of exposure to rabies or tetanus), or shortly before an
exposure is expected, as in the administration of immune
globulin to prevent viral hepatitis A).
Breastfeeding is an example of an intervention that acts at all

three levels of primary prevention:
Health promotion: by providing optimal nutrition for a

young child, either as the sole diet up to four months of
age, or as a supplement in later months.
Prevention of exposure: by reducing exposure of the

child to contaminated milk.
Prevention of disease after exposure: by the provision

of anti-infective factors, including antibodies, white blood
cells, and others.
b. Secondary prevention: After the biological onset of

disease, but before permanent damage sets in, we speak of
secondary prevention. The objective here is to stop or slow
the progression of disease so as to prevent or limit permanent
damage, through the early detection and treatment of disease.
(e.g. breast cancer (prevention of the invasive stage of the
disease), trachoma (prevention of blindness), and syphilis
(prevention of tertiary or congenital syphilis))
18
c. Tertiary prevention: After permanent damage has set in,

the objective of tertiary prevention is to limit the impact of that
damage. The impact can be physical, psychological, social
(social stigma or avoidance by others), and financial.
Rehabilitation refers to the retraining of remaining functions
for maximum effectiveness, and should be seen in a very
broad sense, not simply limited to the physical aspect. Thus
the provision of special disability pensions would be a form of
tertiary prevention.
2.7 Communicable Disease Control
This refers to the reduction of the incidence and prevalence of

communicable disease to a level where it cannot be a major
public health problem.
Methods of Communicable Disease Control

There are three main methods of controlling communicable
diseases:
1. Elimination of the Reservoir

a. Man as reservoir: When man is the reservoir, eradication
of an infected host is not a viable option. Instead, the following
options are considered:
19
Detection and adequate treatment of cases: arrests the

communicability of the disease (e.g. Treatment of active
pulmonary tuberculosis).
Isolation: separation of infected persons for a period of
communicability of the disease. Isolation is indicated for
infectious disease with the following features:
- High morbidity and mortality
- High infectivity
Quarantine: limitation of the movement of apparently well
person or animal who has been exposed to the infectious
disease for a duration of the maximum incubation period
of the disease.
b. Animals as reservoir: Action will be determined by the
usefulness of the animals, how intimately they are associated
to man and the feasibility of protecting susceptible animals.
For example:
Plague: The rat is regarded as a pest and the objective
would be to destroy the rat and exclude it from human
habitation.
Rabies: Pet dogs can be protected by vaccination but
stray dogs are destroyed.
Infected animals used for food are examined and
destroyed.
c. Reservoir in non-living things: Possible to limit man’s

exposure to the affected area (e.g. Soil, water, forest, etc.).
20
2. Interruption of transmission
This involves the control of the modes of transmission from
the reservoir to the potential new host through:
Improvement of environmental sanitation and personal
hygiene
Control of vectors
Disinfections and sterilization
3. Protection of susceptible host: This can be achieved

through:
Immunization: Active or Passive
Chemo-prophylaxis- (e.g. Malaria, meningococcal
meningitis, etc.)
Better nutrition
Personal protection. (e.g. wearing of shoes, use of
mosquito bed net, insect repellents, etc.)
21
Review Questions
1. State the six important factors that involve the chain of

communicable diseases transmission.
2. Describe the three levels of disease prevention.
3. What are the methods used to control communicable
diseases?
22
CHAPTER THREE
ORAL-FECAL TRANSMITTED
DISEASES
At the end of this chapter, students will be able to:

Identify the five important “Fs” in oral-fecal disease
transmission.
State diseases transmitted mainly in water and in soil.
List diseases commonly transmitted by having direct
contact with feces.
Participate in the diagnosis and treatment of cases.
Implement preventive and control methods of oral-fecal
transmitted diseases.
3.2 Introduction
What the diseases in this group have in common is that the

causative organisms are excreted in the stools of infected
persons (or, rarely, animals). The portal of entry for these
diseases is the mouth.
23
Therefore, the causative organisms have to pass through the

environment from the feces of an infected person to the
gastro-intestinal tract of a susceptible person. This is known
as the fece-oral transmission route. Oral-oral transmission
occurs mostly through unapparent fecal contamination of
food, water and hands.
As indicated in the schematic diagram below, food takes a

central position; it can be directly or indirectly contaminated
via polluted water, dirty hands, contaminated soil, or flies.
Water
Feces Soil Food Mouth
Flies
Finger
Fig. 3.1 The five “Fs” which play an important role in fecal oral diseases
transmission (finger, flies, food, fomites and fluid). (From Eshuis,
Manschot,1978, Communicable Diseases: A Manual for Rural Health
Workers, African Medical and Research Association, Nairobi, Kenya)
3.3 Feces Mainly in Water
The diseases in this group are mainly transmitted through

fecally contaminated water rather than food.
24
3.3.1 Typhoid fever
Definition
A systemic infectious disease characterized by high
continuous fever, malaise and involvement of lymphoid
tissues.
Infectious agent
Salmonella typhi
Salmonella enteritidis (rare cause)
Epidemiology
Occurrence- It occurs worldwide, particularly in poor socio-
economic areas. Annual incidence is estimated at about 17
million cases with approximately 600,000 deaths worldwide. In
endemic areas the disease is most common in preschool and
school aged children (5-19 years of age).
Reservoir- Humans
Mode of transmission- By water and food contaminated by

feces and urine of patients and carriers. Flies may infect
foods in which the organisms then multiply to achieve an
infective dose.
Incubation period –1-3 weeks
25
Period of communicability- As long as the bacilli appear in

excreta, usually from the first week throughout
convalescence. About 10% of untreated patients will
discharge bacilli for 3 months after onset of symptoms, and
2%-5% become chronic carriers.
Susceptibility and resistance- Susceptibility is general and

increased in individuals with gastric achlorhydria or those who
are HIV positive. Relative specific immunity follows recovery
from clinical disease, unapparent infection and active
immunization but inadequate to protect against subsequent
ingestion of large numbers of organisms.
Clinical manifestation
First week- Mild illness characterized by fever rising stepwise
(ladder type), anorexia, lethargy, malaise and general aches.
Dull and continuous frontal headache is prominent. Nose
bleeding, vague abdominal pain and constipation in 10% of
patients.
Second week- Sustained temperature (fever). Severe illness

with weakness, mental dullness or delirium, abdominal
discomfort and distension. Diarrhea is more common than first
week and feces may contain blood.
26
Third week- Patient continues to be febrile and increasingly

exhausted. If no complications occur, patient begins to
improve and temperature decreases gradually.
Clinical manifestations suggestive of typhoid fever

Fever- Sustained fever (ladder fashion)
Rose spots- Small pallor, blanching, slightly raised
macules usually seen on chest and abdomen in the first
week in 25% of white people.
Relative bradycardia- Slower than would be expected
from the level of temperature.
Leucopoenia- White cell count is less than 4000/mm3 of
blood.
Diagnosis
Based on clinical grounds but this is confused with wide
variety of diseases.
Widal reaction against somatic and flagellar antigens.
Blood, feces or urine culture.
Treatment
1. Ampicillin or co-trimoxazole for carriers and mild cases.
2. Chloramphenicol or ciprofloxacin or ceftriaxone for
seriously ill patients.
27
Nursing care
1. Maintain body temperature to normal.
2. Apply comfort measures.
3. Follow side effects of drugs.
4. Monitor vital signs.
5. Follow strictly enteric precautions:
wash hands
wear gloves
teach all persons about personal hygiene
6. Observe the patient closely for sign and symptoms of
bowel perforation
erosion of intestinal ulcers
sudden pain in the lower right side of the abdomen
abdominal rigidity
sudden fall of temperature and blood pressure
7. Accurately record intake and output.
8. Provide proper skin and mouth care.
Prevention and control

1. Treatment of patients and carriers
2. Education on handwashing, particularly food handlers,
patients and childcare givers
3. Sanitary disposal of feces and control of flies.
4. Provision of safe and adequate water
5. Safe handling of food.
28
6. Exclusion of typhoid carriers and patients from handling of

food and patients
7. Immunization for people at special risk (e.g. Travelers to
endemic areas)
8. Regular check-up of food handlers in food and drinking

establishments
3.3.2 Bacillary Dysentery (Shigellosis)
Definition
An acute bacterial disease involving the large and distal small
intestine, caused by the bacteria of the genus shigella.
Infectious agent
Shigella is comprised of four species or serotypes.
Group A= Shigella dysentraie (most common cause)
Group B= Shigella flexneri
Group C= Shigella boydii
Group D= Shigella sonnei
Epidemiology
Occurrence- It occurs worldwide, and is endemic in both
tropical and temperate climates. Outbreaks commonly occur
under conditions of crowding and where personal hygiene is
poor, such as in jails, institutions for children, day care
29
centers, mental hospitals and refugee camps. It is estimated

that the disease causes 600,000 deaths per year in the world.
Two-thirds of the cases, and most of the deaths, are in
children under 10 years of age.
Reservoir- Humans
Mode of transmission- Mainly by direct or indirect fecal-oral

transmission from a patient or carrier. Transmission through
water and milk may occur as a result of direct fecal
contamination. Flies can transfer organisms from latrines to a
non-refrigerated food item in which organisms can survive and
multiply.
Incubation period- 12 hours-4 days (usually 1-3 days)
Period of communicability- During acute infection and until

the infectious agent is no longer present in feces, usually
within four weeks after illness.
Susceptibility and resistance- Susceptibility is general. The

disease is more severe in young children, the elderly and the
malnourished. Breast-feeding is protective for infants and
young children.
30
Clinical Manifestation
Fever, rapid pulse, vomiting and abdominal cramp are
prominent.
Diarrhea usually appears after 48 hours with dysentery
supervening two days later.
Generalized abdominal tenderness.
Tenesmus is present and feces are bloody, mucoid and of
small quantity.
Dehydration is common and dangerous - it may cause
muscular cramp, oliguria and shock.
Diagnosis
Based on clinical grounds
Stool microscopy (presence of pus cells)
Stool culture confirms the diagnosis
Treatment
1. Fluid and electrolyte replacement
2. Co-trimoxazole in severee cases or Nalidixic acid in the
case of resistance.

1. Detection of carriers and treatment of the sick will
interrupt an epidemic.
2. Handwashing after toilet and before handling or eating
food.
31
3. Proper excreta disposal especially from patients,

convalescent and carriers.
4. Adequate and safe water supply.
5. Control of flies.
6. Cleanliness in food handling and preparation.
3.3.3 Amoebiasis (Amoebic Dysentery)
Definition
An infection due to a protozoan parasite that causes intestinal
or extra-intestinal disease.
Infectious agent
Entamoeba histolytica
Epidemiology
Occurrence- worldwide but most common in the tropics and
sub-tropics. Prevalent in areas with poor sanitation, in mental
institutions and homosexuals. Invasive amoebiasis is mostly a
disease of young people (adults). Rare below 5 years of age,
especially below 2 years.
Mode of transmission – Fecal-oral transmission by ingestion

of food or water contaminated by feces containing the cyst.
Acute amoebic dysentery poses limited danger.
32
Incubation period- Variable from few days to several months

or years; commonly 2-4 weeks.
Period of communicability- During the period of passing

cysts of E. histolytica, which may continue for years.
Susceptibility and resistance- Susceptibility is general.

Susceptibility to reinfection has been demonstrated but is
apparently rare.
Life cycle
TRANSMISSION
1. Cysts ingested in food, water
or from hands contaminated with
feces.
ENVIRONMENT
6. Feces containing infective cysts
contaminate the environment.
HUMAN HOST
2. cysts excyst, forming
trophozoites
3. Multiply in intestine
4. Trophozoites encyst.
5. Infective cysts passed in
feces.*
* trophozoites passed in feces
disintegrate.
Fig. 3.2 Transmission and life cycle of Entamoeba histolytica. (From Monica
Chesbrough, 1998, District Laboratory Practice in Tropical Countries, Part
One, Cambridge University Press, London.)
33
Starts with a prodormal episode of diarrhea, abdominal
cramps, nausea, vomiting and tenesmus.
With dysentery, feces are generally watery, containing
mucus and blood.
Diagnosis
Demonstration of etamoeba histolytica cyst or trophozoite
in stool.
Treatment
1. Metronidazole or Tinidazole

1. Adequate treatment of cases
2. Provision of safe drinking water
3. Proper disposal of human excreta (feces) and
handwashing following defecation.
4. Cleaning and cooking of local foods (e.g. raw vegetables)
to avoid eating food contaminated with feces.
3.3.4 Giardiasis
Definition
A protozoan infection principally of the upper small intestine
associated with symptoms of chronic diarrhea, steatorrhea,
34
abdominal cramps, bloating, frequent loose and pale greasy

stools, fatigue and weight loss.
Infectious agent
Giardia lamblia
Epidemiology
Occurrence- Worldwide distribution. Children are more
affected than adults. The disease is highly prevalent in areas
of poor sanitation.
Reservoir- Humans
Mode of transmission- Person to person transmission
occurs by hand to mouth transfer of cysts from feces of an
infected individual especially in institutions and day care
centers.
Period of communicability- Entire period of infection, often

months.
Susceptibility and resistance- Asymptomatic carrier rate is

high. Infection is frequently self-limited. Persons with AIDS
may have more serious and prolonged infection.
35
Life cycle
TRANSMISSION
1. Cysts ingested in food,
water or from hands
contaminated with feces.
ENVIRONMENT
6. Feces containing
infective cysts
contaminate the
environment.
HUMAN HOST
2. cysts excyst,
forming
trophozoites
3. Multiply in intestine
4. Trophozoites
encyst.
5. Infective cysts
passed in feces. *
* trophozoites passed in feces
disintegrate.
Fig. 3.3 Transmission and Life Cycle of Giardia Lamblia. (From Monica
Ranges from asymptomatic infection to severe failure to
thrive and mal-absorption.
Young children usually have diarrhea but abdominal
distension and bloating are frequent.
36
Adults have abdominal cramps, diarrhea, anorexia,

nausea, malaise, bloating, many patients complain of
sulphur testing (belching).
Diagnosis
Demonstration of Giardia lamblia cyst or trophozoite in
feces.
Treatment
1. Metronidazole or Tinidazole

1. Good personal hygiene, and handwashing before food
and following toilet use
2. Sanitary disposal of feces
3. Protection of public water supply from contamination of
feces
4. Case treatment
5. Safe water supply
3.3.5 Cholera
Definition
An acute illness caused by an enterotoxin elaborated by vibrio
cholerae.
37
Infectious agent
Vibrio cholerae
Epidemiology
Occurrence- has made periodic outbreaks in different parts of
the world and given rise to pandemics. Endemic
predominantly in children.
Reservoir- Humans
Mode of transmission- by ingestion of food or water directly

or indirectly contaminated with feces or vomitus of infected
person.
Incubation period- from a few hours to 5 days, usually 2-3

days.
Period of communicability- for the duration of the stool

positive stage, usually only a few days after recovery.
Antibiotics shorten the period of communicability.
Susceptibility and resistance- Variable. Gastric achlorhydria

increases risk of illness. Breast-fed infants are protected.
38
Abrupt painless watery diarrhea; the diarrhea looks like
rice water.
In severe cases, several liters of liquid may be lost in few
hours leading to shock.
Severely ill patients are cyanotic, have sunken eyes and
cheeks, scaphoid abdomen, poor skin turgor, and thready
or absent pulse.
Loss of fluid continues for 1-7 days.
Diagnosis
Culture (stool) confirmation
Treatment
1. Prompt replacement of fluids and electrolytes
Rapid IV infusions of large amounts
Isotonic saline solutions alternating with isotonic sodium
bicarbonate or sodium lactate.
2. Antibiotics like tetracycline dramatically reduce the duration
and volume of diarrhea resulting in early eradication of
vibrio cholerae.
Nursing care
1. Wear gown and glove.
2. Wash your hands.
39
3. Monitor output including stool output.

4. Protect the patient family by administering Tetracycline.
5. Health education.

1. Case treatment
2. Safe disposal of human excreta and control of flies
3. Safe public water supply
4. Handwashing and sanitary handling of food
5. Control and management of contact cases
3.3.6 Infectious hepatitis

(Viral hepatitis A, Epidemic hepatitis, type A hepatitis)
Definition
An acute viral disease characterized by abrupt onset of fever,
malaise, anorexia, nausea and abdominal discomfort followed
within a few days by jaundice.
Infectious agent
Hepatitis A virus
Epidemiology
Occurrence- Worldwide distribution in sporadic and epidemic
forms. In developing countries, adults are usually immune and
40
epidemics of HA are uncommon. Infection is common where

environmental sanitation is poor and occurs at an early age.
Reservoir- Humans.
Mode of transmission- Person to person by fecal-oral route.
Through contaminated water and food contaminated by
infected food handlers.
Incubation period- 15-55 days, average 28-30 days.
Period of communicability- High during the later half of the

incubation period and continuing for few days following onset
of jaundice. Most cases are non-infectious following first week
of jaundice.

Immunity following infection probably lasts for life.
Abrupt onset of fever, malaise, anorexia, nausea and
abdominal discomfort, followed in few days by jaundice.
Complete recovery without sequel or recurrence as a rule.
Diagnosis
Based on clinical and epidemiological grounds
41
Demonstration of IgM (IgM anti-HAV) in the serum of

acutely or recently ill patients.
Treatment
Symptomatic: Rest, high carbohydrate diet with low fat and
protein.

1. Public education about good sanitation and personal
hygiene, with special emphasis on careful handwashing
and sanitary disposal of feces.
2. Proper water treatment and distribution systems and
sewage disposal.
3. Proper management of day care centers to minimize
possibility of fecal-oral transmission.
4. HA vaccine for all travelers to intermediate or highly
endemic areas.
5. Protection of day care centers’ employees by vaccine.
3.4 Feces Mainly in Soil
The diseases in this category are mainly transmitted through

fecal contamination of soil. These infections are acquired
through man’s exposure to fecally contaminated soil.
42
3.4.1 Ascariasis
Definition
A helminthic infection of the small intestine generally
associated with few or no symptoms.
Infectious agent
Ascaris lumbricoides.
Epidemiology
Occurrence- The most common parasite of humans where
sanitation is poor. School children (5-10 years of age) are
most affected. Highly prevalent in moist tropical countries
Reservoir- Humans; ascarid eggs in soil.
Mode of transmission- Ingestion of infective eggs from soil

contaminated with human feces or uncooked produce
contaminated with soil containing infective eggs but not
directly from person to person or from fresh feces.
Incubation period- 4-8 weeks.
Period of communicability- As long as mature fertilized

female worms live in the intestine. Usual life span of the adult
worm is 12 months.
43
Life Cycle
TRANSMISSION
1. Infective eggs ingested in
food or from contaminated
hands
ENVIRONMENT
6. Eggs become infective
(embryonated) in soil in 30-40
days.
7. Infective eggs contaminate the
environment.
HUMAN HOST
2. Larvae hatch.
Migrate through liver and lungs.
3. Pass up trachea and are swallowed
4. Become mature worms in small
intestine
5. Eggs produced and passed in
feces.
Fig. 3.4 Transmission and life cycle of Ascaris lumbricoides. (From Monica
Most infections go unnoticed until large worm is passed in

feces and occasionally the mouth and nose.
Migrant larvae may cause itching, wheezing and dyspnea,
fever, cough productive of bloody sputum may occur.
44
Abdominal pain may arise from intestinal or duct (biliary,

pancreatic) obstruction.
Serious complications include bowel obstruction due to
knotted/intertwined worms.
Diagnosis
Microscopic identification of eggs in a stool sample
Adult worms passed from anus, mouth or nose.
Treatment
1. Albendazole or
2. Mebendazole or
3. Piperazine or
4. Levamisole

1. Treatment of cases
3. Prevent soil contamination in areas where children play
4. Promote good personal hygiene (handwashing).
3.4.2 Trichuriasis
Definition
A nematode infection of the large intestine, usually
asymptomatic in nature.
45
Infectious agent
Trichuris trichuria (whip worm)
Epidemiology
Occurrence- Worldwide, especially in warm moist regions.
Common in children 3-11 years of age.
Reservoir- Humans
Mode of transmission- Indirect, particularly through pica or

ingestion of contaminated vegetables. Not immediately
transmissible from person to person.
Incubation period- Indefinite
Period of communicability- Several years in untreated

carriers.
Susceptibility and resistance- Susceptibility is universal.
46
Life Cycle
TRANSMISSION
1. Infective eggs ingested in food
or from contaminated hands
ENVIRONMENT
6. Eggs become infective
(embryonated) in soil after 3
weeks.
7. Infective eggs contaminate the
environment
HUMAN HOST
2. Larvae hatch.
Develop in small intestine.
Migrate to caecum.
3. Become mature worms.
4. Eggs produced and passed
in feces.
Fig. 3.5 Transmission and life cycle of Trichuris trichuria. (From Monica
Severity is directly related to the number of infecting
worms.
Most infected people are asymptomatic.
Abdominal pain, tiredness, nausea and vomiting, diarrhea
or constipation are complaints by patients.
Rectal prolapse may occur in heavily infected very young
children.
47
Diagnosis
Demonstration of eggs in feces.
Treatment
1. Albendazole or
2. Mebendazole

2. Maintaining good personal hygiene (i.e. washing hands
and vegetables and other soil contaminated foods)
3. Cutting nails especially in children
4. Treatment of cases.
3.4.3 Entrobiasis
(Oxyuriasis, pinworm infection)
Definition
A common intestinal helminthic infection that is often
asymptomatic.
Infectious agent
Entrobius vermicularis
48
Epidemiology
Occurrence- Worldwide, affecting all socio-economic classes
with high rates in some areas. Prevalence is highest in
school-aged children, followed by preschools and is lowest in
adults except for mothers of infected children. Prevalence is
often high in domiciliary institutions. Infection usually occurs in
more than one family member.
Reservoir- Human
Mode of transmission- Direct transfer of infective eggs by

hand from anus to mouth of the same or another person or
indirectly through clothing, bedding, food or other articles
contaminated with eggs of the parasite.
Incubation period- 2-6 weeks
Period of communicability- As long as gravid females are

discharging eggs on perianal skin. Eggs remain infective in an
indoor environment for about 2 weeks.
49
Life Cycle
Gravid females migrate through the
Adult worms anus to the perianal skin and
in Caecum deposit eggs (usually during the
night)
2-3 weeks
Eggs become infective in a few
hours in perianal area
Larvae
Migrate down
hatch in
To caecum Ingestion of eggs by Man
duodenum
Fig. 3.6 Transmission and life cycle of Entrobius vermicularis. (From Hegazi
st
M., 1994, Applied Human Parasitology, 1 edition, the Scientific Book
Centers, Cairo.)
Perianal itching, disturbed sleep, irritability and some
times secondary infection of the scratched skin.
Diagnosis
Stool microscopy for eggs or female worms.
Treatment
1. Mebendazole.

1. Educate the public about hygiene (i.e. handwashing
before eating or preparing food, keeping nails short and
discourage nail biting).
3. Reduce overcrowding in living accommodations.
4. Provide adequate toilets.
50
3.4.4. Strongyloidiasis
Definition
An often asymptomatic helminthic infection of the duodenum
and upper jejunum.
Infectious agent
Strongyloides stercolaris
Epidemiology
Occurrence- In tropical and temperate areas. More common
in warm and wet regions.
Reservoir- Human
Mode of transmission- Infective (filariform) larvae penetrate

the skin and enter the venous circulation.
Incubation period- 2-4 weeks (from skin penetration up to

when rhabditi form larvae appear in the feces).
Period of communicability- As long as living worms remain

in the intestine; up to 35 years in cases of auto-infection.

Patients with AIDS or on immuno-suppressive medication are
at risk of dissemination.
51
Life Cycle
TRANSMISSION
1. Infective filariform larvae
penetrate skin, e.g. feet.
Autoinfection also occurs.
ENVIRONMENT
6. In soil larvae become free-
living worms produce more
HUMAN HOST rhabditiform larvae*
2. Larvae migrate, pass up trachea * Free-living cycle can be
and are swallowed. repeated several times
3. Become mature worms in small 7. Become infective filariform
intestine larvae in the soil
4. Eggs laid. Hatch rhabditiform
larvae in intestine.
5. Rhabditiform larvae:
- Passed in feces, or
- Become filariform larvae in
intestine, causing
atutoinfection.
Fig. 3.7 Transmission and life cycle of Strongyloides stercoralis. (From

Monica Chesbrough, 1998, District Laboratory Practice in Tropical Countries,
Part One, Cambridge University Press, London.)
Pneumonia occurs during heavy larval migration.
Mild peptic ulcer like epigastric discomfort to severe
watery diarrhea.
Heavy infection may result in malabsorption syndrome.
Diagnosis
Identification of larvae in stool specimen.
52
Treatment
1. Albendazole or
2. Thiabendazole

1. Proper disposal of human excreta (feces)
2. Personal hygiene including use of footwear.
3. Case treatment.
3.4.5 Hookworm disease

(Ancylostomiasis, Necatoriasis)
Definition
A common chronic parasitic infection with a variety of
symptoms usually in proportion of the degree of anemia
Infectious agent
Ancylostoma duodenale and
Necator americanus
Epidemiology
Occurrence- Widely endemic in tropical and subtropical
countries where sanitary disposal of human feces is not
practiced and the soil moisture and temperature conditions
favor development of infective larvae.
Reservoir- Humans
53
Mode of transmission- Through skin penetration by the

infective larvae.
Incubation period- Symptoms may develop after a few

weeks to many months depending on intensity of infection and
iron intake of the host.
Period of communicability- Infected people can contaminate

the soil for several years in the absence of treatment.
Susceptibility and resistance- Susceptibility is universal. No

evidence that immunity develops with infection.
Life cycle
TRANSMISSION
1. Infective filariform larvae penetrate the
skin, e.g. feet.
A. duodenale also transmitted by
ingestion of larvae.
ENVIRONMENT
5. Eggs develop; Rhabditiform
larvae hatch. Feed in soil.
6. Develop into infective filariform
HUMAN HOST larvae in about 1 week.
2. Larvae migrate. Pass up trachea 7. Filariform larvae contaminate soil.
and are swallowed.
3. Become mature worms in small
intestine (attach to wall and suck
blood).
4. Eggs produced and passed in
feces.
Fig. 3.8 Transmission and life cycle of Hookworms: Ancylostoma duodenale

and Nectar americanus. (From Monica Chesbrough, 1998, District Laboratory
Practice in Tropical Countries, Part One, Cambridge University Press,
London.)
54
The clinical manifestation is related to:
1. Larval migration of the skin
Produces transient, localized maculopapular rash
associated with itching called ground itch.
2. Migration of larva to the lungs.
Produces cough, wheezing and transient pneumonitis.
3. Blood sucking
Light infection-no symptoms
Heavy infection-result in symptoms of peptic ulcer disease
like epigastric pain and tenderness. Further loss of blood
leads to anemia manifested by exertional dyspenea,
weakness and light-headedness.
Diagnosis
Demonstration of eggs in stool specimen.
Treatment
1. Mebendazole or
2. Albendazole or
3. Levamisole

2. Wearing of shoes
3. Case treatment.
55
3.5 Direct Contact with Feces
These are diseases transmitted mainly through direct contact

with feces of the infected person.
3.5.1 Poliomyelitis
Definition
A viral infection most often recognized by the acute onset of
flaccid paralysis.
Infectious agent
Polio viruses (type I, II and III)
Epidemiology
Occurrence – Worldwide prior to the advent of immunization.
Cases of polio occur both sporadically and in epidemics.
Primarily a disease of infants and young children. 70-80% of
cases are less than three years of age. More than 90% of
infections are unapparent. Flaccid paralysis occurs in less
than 1% of infections.
Reservoir – humans, especially children
Mode of transmission- Primarily person-to-person, spread

principally through the fecal-oral route. In rare instances, milk,
56
food stuffs and other materials contaminated with feces have

been incriminated as vehicles.
Incubation period- commonly 7-14 days
Period of communicability – not precisely known, but

transmission is possible as long as the virus is excreted.
Susceptibility and resistance- Susceptibility is common in

children but paralysis rarely occurs. Infection confers
permanent immunity.
Usually asymptomatic or non-specific fever is manifested
in 90% of cases.
If it progresses to major illness, severe muscle pain, stiff
neck and back with or without flaccid paralysis may occur.
Paralysis is asymptomatic and occurs within three to four
days of illness.
The legs are more affected than other part of the body.
Paralysis of respiratory and swallowing muscles is life-
threatening.
Diagnosis
57
Treatment
Symptomatic

1. Educate public about the advantage of immunization in
early childhood.
2. Trivalent live attenuated vaccine (OPV) at birth.
3. Safe disposal of human excreta (feces).
3.5.2 Hydatid Disease (Echinococcosis)
Definition
The tapeworm Echinococcus granulosus is the most common
species of Echinococcus and causes cystic hydatid disease.
Infectious agent
Echinococcus granulosus, a small tapeworm of dog
Epidemiology
Occurrence – occurs on all continents except Antarctica.
Especially common in grazing countries where dogs consume
viscera containing cysts.
Reservoir- Domestic dogs and other canids are definitive

hosts; they may harbor thousands of adult tapeworms in their
58
intestines without signs of infection. Sheep act as intermediate

hosts.
Mode of transmission – directly with hand to mouth transfer

of eggs after association with infected dogs or indirectly
through contaminated food, water, soil or fomites.
Incubation period – variable from 12 months to many years,

depending on the number and location of cysts and how
rapidly they grow.
Period of communicability – Infected dogs begin to pass

eggs approximately 7weeks after infection. Most canine
infections resolve spontaneously by six months.
Susceptibility and resistance – Children are more likely to

be exposed to infection because they are more likely to have
close contact with infected dogs.
Clinical manifestations
The signs and symptoms vary according to location of the
cyst and number.
Ruptured or leaking cysts can cause severe anaphylactic
reactions.
Cysts are typically spherical, thick walled and unilocular
and are most frequently found in the liver and lungs.
59
Diagnosis
History of residence in an endemic area along with
association with canines
Sonography and CT scan
Serologic test
Treatment
1. Surgical resection of isolated cysts is the most common
treatment.
2. Albendazol (mebendazol)
3. If cysts rupture, praziquantel

1. Educate the public at risk to avoid exposure to dog feces.
Handwashing should be emphasized.
2. Interrupt transmission from intermediate to definitive hosts
by preventing dogs’ access to uncooked viscera.
3. Safe disposal of infected viscera.
4. Periodical treatment of high-risk dogs.
60
Review Questions
1. What does fecal-oral transmission mean?

2. Mention some of the diseases transmitted through
unapparent fecal contamination of food, water and
hands.
3. State some of the common preventive and control
measures of oral-fecal transmitted diseases.
61
CHAPTER FOUR
AIR-BORNE DISEASES
At the end of this chapter, students will be able to:

- List common air-borne diseases.
- Identify the common modes of air-borne diseases
transmission.
- Participate in diagnosis and treatment of common air-
borne diseases.
- Apply preventive and control methods for air-borne
diseases.
4.2 Introduction
The organisms causing the diseases in the air-borne group

enter the body via the respiratory tract. When a patient or
carrier of pathogens talks, coughs, laughs, or sneezes, he/she
discharges fluid droplets. The smallest of these remain up in
the air for some time and may be inhaled by a new host.
Droplets with a size of 1-5 microns are quite easily drawn in to
the lungs and retained there.
62
Droplets that are bigger in size will not remain air-borne for
long but will fall to the ground. Here, however, they dry and
mix with dust. When they contain pathogens that are able to
survive drying, these may become air-borne again by wind or
something stirring up the dust, and they can then be inhaled.
Air-borne diseases, obviously, will spread more easily when
there is overcrowding, as in overcrowded class rooms, public
transport, canteens, dance halls, and cinemas. Good
ventilation can do much to counteract the effects of
overcrowding. Air-borne diseases are mostly acquired through
the respiratory tract.
4.3 Common Cold (Acute Viral Rhinitis or

Coryza)
Definition
An acute catarrhal infection of the upper respiratory tract.
Infectious agent
Rhino viruses (100 serotypes) are the major causes in adults.
Parainfluenza viruses, respiratory syncytial viruses (RSV),
Influenza, and Adeno viruses cause common cold-like
illnesses in infants and children.
63
Epidemiology
Occurrence- Worldwide both in endemic and epidemic forms.
Many people have one to six colds per year. Greater
incidence in the highlands. Incidence is high in children under
5 years and gradually declines with increasing age.
Reservoir- Humans
Mode of transmission- by direct contact or inhalation of

airborne droplets. Indirectly by hands and articles freshly
soiled by discharges of nose and throat of an infected person.
Incubation period- between 12 hours and 5 days, usually 48

hours, varying with the agent.
Period of communicability- 24 hours before onset and for 5

days after onset.

Repeated infections (attacks) are most likely due to multiplicity
of agents.
Coryza, sneezing, lacrimation, pharyngeal or nasal
irritation, chills and malaise
Dry or painful throat.
64
Diagnosis
Treatment
1. No effective treatment but supportive measures like
:
Bed rest
Steam inhalation
High fluid intake
Anti pain
Balanced diet intake
Prevention and Control

1. Educate the public about the importance of:
Handwashing
Covering the mouth when coughing and sneezing
Sanitary disposal of nasal and oral discharges
2. Avoid crowding in living and sleeping quarters especially
in institutions
3. Provide adequate ventilation
4.4 Measles (Rubella)
Definition
An acute highly communicable viral disease
Infectious agent
Measles virus
65
Epidemiology
Occurrence- Prior to widespread immunization, measles was
common in childhood so that more than 90% of people had
been infected by age 20; few went through life without any
attack.
Reservoir- Humans
Mode of transmission- Airborne by droplet spread, direct

contact with nasal or throat secretions of infected persons and
less commonly by articles freshly solid with nose and throat
secretion. Greater than 94% herd immunity may be needed to
interrupt community transmission.
Incubation period- 7-18 days from exposure to onset of

fever.
Period of communicability- slightly before the prodromal

period to four days after the appearance of the rash and
minimal after the second day of rash.
Susceptibility and resistance- All those who are non-

vaccinated or have not had the disease are susceptible.
Permanent immunity is acquired after natural infection or
immunization.
66
Prodromal fever, conjunctivitis, coryza, cough and Koplik
spots on the buccal mucosa
A characteristic red blotchy rash appears on the third to
seventh day, beginning on the face, gradually becoming
generalized, lasting 4-7 days.
Leucopoenia is common.
Complications like otitis media, pneumonia, diarrhea,
encephalitis, croup (Laryngo tracheo bronchitis) may
result from viral replication or bacterial super infection.
Diagnosis
Treatment
1. No specific treatment
2. Treatment of complications
3. Vitamin A provision
Nursing care
1. Advise patient to have bed rest.
2. Relief of fever.
3. Provision of non-irritant small frequent diet.
4. Shorten the fingernails.

1. Educate the public about measles immunization.
67
2. Immunization of all children (less than 5 years of age)

who had contact with infected children.
3. Provision of measles vaccine at nine months of age.
4. Initiate measles vaccination at 6 months of age during
epidemic and repeat at 9 months of age.
4.5 Influenza
Definition
An acute viral disease of the respiratory tract
Infectious agent
Three types of influenza virus (A,B and C)
Epidemiology
Occurrence- In pandemics, epidemics and localized
outbreaks.
Reservoir- Humans are the primary reservoirs for human

infection.
Mode of transmission- Airborne spread predominates

among crowded populations in closed places such as school
buses.
Incubation period- short, usually 1-3 days
68
Period of communicability- 3-5 days from clinical onset in

adults; up to 7 days in young children.
Susceptibility and resistance- when a new sub-type

appears, all children and adults are equally susceptible.
Infection produces immunity to the specific infecting agent.
Fever, head ache, mayalgia, prostration, sore throat and
cough
Cough is often severe and protracted, but other
manifestations are self-limited with recovery in 2-7days
Diagnosis
Based on clinical ground
Treatment
1. Same as common cold, namely:
Anti-pain and antipyretic
High fluid intake
Bed rest
Balanced diet intake

1. Educate the public in basic personal hygiene, especially
the danger of unprotected coughs and sneezes and hand
to mucus membrane transmission.
69
2. Immunization with available killed virus vaccines may

provide 70-80% protection.
3. Amantadize hydrochloride is effective in the
chemprophylaxis of type A virus but not others.
4.6 Diphtheria
Definition
An acute bacterial disease involving primarily tonsils, pharynx,
nose, occasionally other mucus membranes or skin and
sometimes the conjunctiva or genitalia.
Infectious agent
Corynebacterium diphtheriae
Epidemiology
Occurrence- Disease of colder months in temperate zones,
involving primarily non-immunized children under 15 years of
age. It is often found among adult population groups whose
immunization was neglected. Unapparent, cutaneous and
wound diphtheria cases are much more common in the
tropics.
Reservoir- Humans
Mode of transmission- contact with a patient of carrier. i.e.

with oral or nasal secretions or infected skin.
70
Incubation period- usually 2-5 days
Period of communicability- variable, until virulent bacilli

have disappeared from discharges and lesion; usually 2
weeks or less.

Infants borne to immune mothers are relatively immune, but
protection is passive and usually lost before 6 months.
Recovery from clinical disease is not always followed by
lasting immunity. Immunity is often acquired through
unapparent infection. Prolonged active immunity can be
induced by diphtheria toxoid.
Characteristic lesion marked by a patch or patches of an
adherent grayish membrane with a surrounding
inflammation (pseudo membrane).
Throat is moderately sore in pharyngo tonsillar diphtheria,
with cervical lymph nodes somewhat enlarged and tender;
in severe cases, there is marked swelling and edema of
neck.
Late effects of absorption of toxin appearing after 2-6
weeks, including cranial and peripheral, motor and
sensory nerve palsies and myocarditis (which may occur
early) and are often severe.
71
Diagnosis
Bacteriologic examination of discharges from lesions.
Treatment
1. Diphtheria antitoxin
2. Erythromycin for 2 weeks but 1 week for cutaneous form
or
3. Procaine penicillin for 14 days or single dose of Benzathin
penicillin
Primary goal of antibiotic therapy for patients or carriers is to

eradicate C. diphtheriae and prevent transmission from the
patient to susceptible contacts.

1. Educate the public, and particularly the parents of young
children, of the hazards of diphtheria and the necessity for
active immunization.
2. Immunization of infants with diphtheria toxoid.
3. Concurrent and terminal disinfection of articles in contact
with patient and soiled by discharges of patient.
4. Single dose of penicillin (IM) or 7-10 days course of
Erythromycin (PO) is recommended for all persons
exposed to diphtheria.
72
4.7 Pertusis (whooping cough)
Definition
An acute bacterial disease involving the respiratory tract.
Infectious agent
Bordetella pertusis
Epidemiology
Occurrence- An endemic disease common to children
especially young children everywhere in the world. A marked
decline has occurred in incidence and mortality rates during
the past four decades. Outbreaks occur periodically. Endemic
in developing world and 90% of attacks occur in children
under 6 yearsof age.
Reservoir- Humans
Mode of transmission- Primarily by direct contact with

discharges from respiratory mucus membranes of infected
persons by airborne route, probably by droplets. Indirectly by
handling objects freshly solid with nasopharyngeal secretions.
73
Period of communicability- Highly communicable in early

catarrhal stage before the paroxysmal cough stage. The most
contagious disease with an attack rate of 75-90%. Gradually
decreases and becomes negligible in about 3 weeks. When
treated with erythromycin, infectiousness is usually 5 days or
less after onset of therapy.
Susceptibility and resistance- Susceptibility to non-

immunized individuals is universal. One attack usually confers
prolonged immunity but may not be lifelong.
The disease has insidious onset and 3 phases:
1. Catarrhal phase
Lasts 1-2 weeks
Cough and rhinorrhea
2. Paroxysmal phase
Explosive, repetitive and prolonged cough
Child usually vomits at the end of paroxysm
Expulsion of clear tenacious mucus often followed by
vomiting
Whoop (inspiratory whoop against closed glottis)
between paroxysms.
Child looks healthy between paroxysms
Paroxysm of cough interferes with nutrition and cough
Cyanosis and sub conjunctiva hemorrhage due to
violent cough.
74
3. Convalescent phase
The cough may diminish slowly or may last long time.
After improvement the disease may recur.
Diagnosis
Difficult to distinguish it from other URTI
History and physical examination at phase two
(paroxysmal phase) ensure the diagnosis.
Marked lymphocytosis.
Treatment
1. Erythromycin- to treat the infection in phase one but to
decrease transmission in phase two
2. Antibiotics for super infections like pneumonia because of
bacterial invasion due to damage to cilia.
Nursing care
1. Proper feeding of the child.
2. Encourage breastfeeding immediately after an attack
(each paroxysm).
3. Proper ventilation- continuous well humidified oxygen
administration.
4. Reassurance of the mother (care giver),
75

1. Educate the public about the dangers of whooping cough
and the advantages of initiating immunization at 6 weeks
of age.
2. Consider protection of health workers at high risk of
exposure by using erythromycin for 14 days.
4.8 Pneumococcal pneumonia
Definition
An acute bacterial infection of the lung tissue and bronchi.
Infectious agent
Streptococcus pneumoniae (pneumococcus)
Epidemiology
Occurrence- Endemic particularly in infancy, old age and
persons with underlying medical conditions. Epidemics can
occur in institutions, barracks and on board ship where people
are living and sleeping in close quarters. Common in lower
socio-economic groups and developing countries.
Reservoir- Humans - pneumococci are usually found in the

URT of healthy people throughout the world.
76
Mode of transmission- droplet spread, direct oral contact or

indirectly through articles freshly soiled with respiratory
discharges. Person to person transmission is common.
Incubation period- not well determined, may be as short as

1-3 days.
Period of communicability- Until discharges of mouth and

nose no longer contain virulent pneumococci in significant
number.
Susceptibility and resistance- Susceptibility is increased by

influenza, pulmonary edema of any cause, aspiration following
alcohol intoxication, chronic lung disease, exposure to irritants
in the air, etc. Malnutrition and low birth weight are important
risk factors in infants and young children in developing
countries. Immunity following an attack may last for years.
Sudden onset of chill, fever, pleural pain, dyspnea,
tachypnea, a cough productive of rusty sputum,
Chest indrawing, shallow and rapid respiration in infants
and young children.
Vomiting and convulsion may occur in infants and young
children.
77
Diagnosis
Chest X-ray- reveals consolidation of the affected lung
tissue but not in children.
Sputum gram stain- reveals gram negative diplococci
Treatment
1. Antipyretic and antipain
2. Antibiotics like Ampicillin or procaine penicillin for adults
but usually crystalline penicillin for children
3. Anticonvulsants for infants.
Nursing care
1. Monitor vital signs especially of children.
2. Maintain high body temperature to normal.
3. Intermittent administration of humidified oxygen if
indicated especially for young children.
4. Timely administration of ordered medication.

2. Treatment of other underlying medical conditions
3. Improved standard of living (adequate and ventilated
housing and better nutrition)
4. Avoid overcrowding.
78
4.9 Meningococcal Meningitis
Definition
An acute bacterial disease that causes inflammation of the pia
and arachnoid space.
Infectious agent
Neisseria meningitides (the meningococcus)
Epidemiology
Occurrence- Greatest incidence occurs during winter and
spring. Epidemics occur irregularly. Common in children and
young adults. It is also common in crowded living conditions.
Reservoir- Humans
Mode of transmission- Direct contact with respiratory

droplets from nose and throat of infected person.
Incubation period- 2-10 day, commonly 3-4 days.
Period of communicability- as long as the bacteria is

present in the discharge.
Susceptibility and resistance- Susceptibility is low and

decreases with age
79
Sudden onset of fever, intense headache, nausea and
often vomiting, neck stiffness and frequently, petechial
rash with pink macules.
Kernig’s sign may be positive (i.e. patient feels back pain
when one of the lower limbs is flexed at the knee joint and
extended forward in an elevated position)
Brudinski’s sign may be positive (i.e. when the patient’s
neck is flexed, the two lower extremities get flexed or
raised up).
Delirium and coma often appear.
Diagnosis
White blood cell count. (neutrophils)
Cerebrospinal fluid analysis (Gram stain, white cell count,
etc.)
Treatment
1. Admit the patient and administer high dose of crystalline
penicillin intravenously
2. Antipyretic
Nursing care
1. Maintain fluid balance (input and output)
2. Maintain body temperature to normal
80
3. Timely administration of antibiotics

4. Monitor vital signs.

1. Educate the public on the need to reduce direct contact
and exposure to droplet infection.
2. Reduce overcrowding in work places, schools, camps,
etc.
3. Vaccines containing group A,C and Y strains.
4. Chemotherapy of cases.
5. Chemo prophylaxis (e.g.Rifampin for 2 days)
6. Report to the concerned health authorities.
4.10 Tuberculosis
Definition
A chronic and infectious mycobacterial disease important as a
major cause of illness and death in many parts of the world.
Infectious agent.
Mycobacterium tuberculosis- human tubercle bacilli
(commonest cause)
Mycobacterium bovis- cattle and man infection
Mycobacterium avium- infection in birds and man.
81
Epidemiology
Occurrence- Worldwide, however underdeveloped areas are
more affected. Affects all ages and both sexes. Age groups
between 15-45 years are mainly affected. According to the
WHO 1995 report, 9 million cases and 3 million deaths have
occurred. According to the Ministry of Health report in 1993
E.C, tuberculosis was a leading cause of outpatient morbidity
(ranked 8th with 2.2%), leading cause of hospitalization
(ranked 3rd with 7.8%) and leading cause of hospital death
(ranked 1st with 10.1%). Tuberculosis has two major clinical
forms. Pulmonary (80%) primarily occurs during childhood
and secondarily 15-45 years or later. The other is extra
pulmonary, which affects all parts of the body. Most common
sites are lymph nodes, pleura, Genitourinary tract, bone and
joints, meninges and peritoneum.
Mode of transmission- Through aerosolized droplets mainly

from persons with active ulcerative lesion of lung expelled
during talking, sneezing, singing, or coughing directly.
Untreated pulmonary tuberculosis positive (PTB+) cases are
the source of infection. Most important is the length of time of
contact an individual shares volume of air with an infectious
case. That is intimate, prolonged or frequent contact is
required. Transmission through contaminated fomites
(clothes, personal articles) is rare. Ingestion of unpasteurized
82
milk transmits bovine tuberculosis. Overcrowding and poor

housing conditions favor the disease transmission.
Period of communicability- as far as the bacilli is present in

the sputum
Susceptibility and resistance- under 3 years old children,

adolescents, young adults, the very old and the immuno-
suppressed are susceptible. Everyone who is non-infected or
non-vaccinated can be infected.
HIV is an important risk factor for the development of HIV-

associated tuberculosis by facilitating:
Reactivation or
Progression of recent infection or
Reinfection
Pulmonary tuberculosis
Persistent cough for 3 weeks or more
Productive cough with or without blood-stained sputum
Shortness of breath and chest pain
Intermittent fevers, night sweats, loss of weight, loss of
appetite, fatigue and malaise.
83
TB lymph adenitis
Slowly developing and painless enlargement of lymph
nodes followed by matting and drainage of pus.
Tuberculosis pleurisy
Pain while breathing in, dull lower chest pain, slight
cough, breathlessness on exertion.
TB of bones and joints

Localized pain and/or swelling, discharging of pus, muscle
weakness, paralysis and stiffness of joints.
Intestinal TB
Loss of weight and appetite
Abdominal pain, diarrhea and constipation
Mass in the abdomen
Fluid in the abdominal cavity (ascites)
Tuberculos meningitis
Headache, fever, vomiting, neck stiffness and mental
confusion of insidious onset.
Diagnosis
1. Clinical manifestations
2. Sputum smears for acid-fast bacilli (AFB), which is the
Golden standard. However, one positive result does not
84
justify starting anti TB treatment since errors can never be

excluded.
3. Acid-fast stain for AFB can be done for extra pulmonary
tuberculosis having pus-y discharge.
4. Radiological examination: This is unreliable because it
can be caused by a variety of conditions or previous TB
patients who are healed may have chest x-ray giving the
appearance of active TB, which requires treatment.
5. Histopathological examination: Biopsies for
extrapulmonary TB (e.g. Tuberculos lymphadenitis)
6. Tuberculin test (mantoux): Helpful in non-BCG vaccinated
children under 6 years of age
7. Culture: Complex and sophisticated tool, which takes
several weeks to yield results. Not a primary diagnostic
tool in our country.
Treatment
The following drugs are being used for treatment of TB in
Ethiopia.
Streptomycin (s) daily IM injection
Ethambutol(E)
Rifampin (R)
Thiacetazone (T)
Isoniazid (H)
Pyrazinamide (Z)
85
All drugs, except streptomycin, which is administered daily

through in route) are to be taken orally as a single daily dose
preferably on an empty stomach.
Drug regimens (prescribed course of therapy)
1) Short course chemotherapy regimen

(DOTS) intensive phase- S(RH)Z for two months
Continuation phase- TH (EH) for the next 6 months.
2) Long course chemotherapy regimen.
Intensive phase- S(TH)or S(EH) for 2 months
Continuation phase-TH or EH for the next 10 months
Nursing care
1. Educate the patient how and when to take the prescribed
medication.
2. Tell the patient not to stop the medication unless he/she is
told to do so.
3. Tell the patient to come to the health institution if he/she
develops drug side effects.
4. Advice the patient on the importance of taking adequate
and balanced diet and to eat what is available at home.

1. Chemotherapy of cases
2. Chemoprophylaxis for contacts
86
INH (Isoniazid) for adults and children who have close

contact with the source of infection
3. Immunization of infants with BCG
4. Educate patients with TB about the mode of disease
transmission and how to dispose their sputum and cover
their mouth while coughing, sneezing, etc.
5. Public health education about the modes of disease
transmission and methods of control
Improved standard of living
Adequate nutrition
Health housing
Environmental sanitation
Personal hygiene; etc.
Active case finding and treatment
4.11 Leprosy (Hansen’s disease)
Definition
A chronic bacterial disease of the skin, peripheral nerves and,
in lepromatous patients, the upper airway
Infectious agent
Mycobacterium leprae
87
Epidemiology
Occurrence- Although common in rural tropics and
subtropics, socio-economic conditions may be more important
than climate itself. Endemic in south and southeast Asia,
tropical Africa and Latin America.
Reservoir- Humans
Mode of transmission- Not clearly established. Household

and prolonged close contact appear to be important. Millions
of bacilli are liberated daily in the nasal discharges of
untreated lepromatous patients. Cutaneous ulcers in
lepromatous patients may shed large number of bacilli.
Organisms probably gain access (entrance) through the URT
and possibly through broken skin. In children less than one
year of age, transmission is presumed to be transplacental.
Incubation period- 9 months to 20 years.
Period of communicability- Infectiousness is lost in most

instances within 3months of continuous and regular treatment
with dapsone or clofazamin or within 3 days of rifampicin
treatment.
88
Susceptibility and resistance- The presence and form of

leprosy depend on the ability to develop effective cell-
mediated immunity.
Clinical manifestations vary between two polar forms:
lepromatous and tuberculoid leprosy.
Lepromatous (Multibacillary form)

Nodules, papules, macules and diffused infiltration are
bilaterally symmetrical and usually numerous and extensive.
Involvement of the nasal mucosa may lead to crusting,
obstructed breathing and epistaxis. Occular involvement leads
to iritis and keratitis.
Tuberculoid (Paucibacillary form)

Skin lesions are single or few, sharply demarcated, anesthetic
or hyperesthetic and bilaterally symmetrical. Peripheral nerve
involvement tends to be severe.
Borderline
Has features of both polar forms and is more liableto shift
toward the lepromatous form in untreated patients and toward
the tuberculoid form in treated patients.
89
Diagnosis
Complete skin examination (hyperesthesia, anesthesia,
paralysis, muscle wasting or trophic ulcer which are signs
of peripheral nerve involvement) with bilateral palpation of
peripheral nerves (ulnar nerve at the elbow, peroneal
nerve at head of fibula and the great auricular nerve) for
enlargement and tenderness.
Skin lesion are tested for sensation (light touch, pink
prick, temperature discrimination).
Demonstration of AFB in skin smears made by scraped
incision method.
Skin biopsy confined to the affected area should be sent
to the experienced pathologists in leprosy diagnosis.
Treatment
1. Dapsone three drugs for 12 months and then
2. Refampicin dapsone alone for the next 12 months.
3. Clfazamin
4. Aspirin for mild reactions and inflammation
5. Severe reaction can be treated with corticosteroids
90
Review Questions
1. What do you understand by air-borne disease

transmission?
2. Which airborne disease occurrence should be reported
immediately to the concerned health authorities for their
prompt action?
a. Pneumonia
b. Tuberculosis
c. Leprosy
d. Meningococcal meningitis
3. Select diseases which cause chronic illness:
a. Tuberculosis
b. Leprosy
c. Measles
d. Infection hepatitis
4. State some of the preventive and control methods for
tuberculosis.
91
CHAPTER FIVE
ARTHROPOD OR INTERMEDIATE
VECTOR-BORNE DISEASES

Describe what arthropod or intermediate vector-borne
disease means.
Identify the common vectors which transmit disease to
man.
List the common vector-borne diseases.
Participate in diagnosis and treatment of vector-borne
diseases.
Implement the common preventive and control methods
of vector-borne diseases.
5.2 Introduction
Generally speaking a vector is any carrier of disease, but in

the case of the ‘vector-borne diseases’ we restrict the word to
those invertebrate hosts (insects or snails), which are an
92
essential part of the life cycle of the disease organism. A

housefly just carrying bacteria or amoebic cysts on its feet to
food is not regarded as a vector: this would be simple
mechanical spread.
Insect vectors usually acquire the disease organism by

sucking blood from infected persons, and pass it on, later, by
the same route. There are other routes, however; infection
may enter skin cracks or abrasions either from infected feces
deposited when feeding, or from body fluid when an insect is
crushed.
By definition the disease organism undergoes a period of

development inside the vector, and the time taken for this is
called the extrinsic incubation period.
5.3 Mosquito-Borne Diseases
5.3.1 Malaria
Definition
An acute infection of the blood caused by protozoa of the
genus plasmodium.
93
Infectious agent.
Plasmodium falciparum/malignant tertian: Invades all
ages of red blood cells. Red blood cell cycle is 48 hours
Plasmodium vivax/benign tertian: Invades reticulocytes
only. Red blood cell cycle is 48 hours.
Plamodium ovale/tertian: Invades reticulocytes only. Red
blood cell cycle is 48 hours.
Plasmodium Malariae/Quartan malaria: Invades
reticulocytes only. Red blood cell cycle is 72 hours.
Epidemiology
Occurrence- Endemic in tropical and sub-tropical countries of
the world. Affects 40% of the world population. Children less 5
years of age, pregnant women and travelers to endemic areas
are risk groups. Plasmodium falciparum 60% and vivax 40%
are common in Ethiopia.
Predisposing factors are:

Environment- physical environment for the propagation
Patient source
Susceptible recipients
Anopheles capable to transmit the parasite
Socio-economic factors like immigration, war, poverty,
ignorance, agricultural irrigation farms, etc.
94
Reservoir- Humans
Mode of transmission- By the bite of an infective female

anopheles mosquito, which sucks blood for egg maturation.
Blood transfusion, hypodermic needles, organ transplantation
and mother to fetus transmission is possible. Since there is no
pre-erythrocytic (tissue) cycle, the incubation period is short.
Anopheles gambae and funestus are common vectors in
Ethiopia.
Incubation period- Varies with species

Plasmodium falciparum 7-14 days
Plasmodium virvax 8-14 days
Plasmodium ovale 8-14 days
Plasmodium malariae 7-30 days
Period of communicability- Mosquitoes are infective as long

as infective gametocytes are present in the blood of patients.
Once infected, mosquito remains infective for life.
Susceptibility and resistance- Susceptibility is universal

except in some host-resistance factors:
Non specific factors

Increased splenic clearance reaction
Hyperpyrexia- which is said to be schizontcidal
Sickle cell traits are resistant to plasmodium falciparum
95
Duffy blood group deficiency (Duffy antigen negative red

blood cells) lack receptor for plasmodium vivax.
Because of passive immunity infants are resistant in early
life.
Specific factors
This is a humoral and cell mediated immunity that is species
and strain specific, and hard-won after repeated infection.
Life cycle
TRANSMISSION
1. Sporozoites inoculated when Anopheles
mosquito takes a blood meal.
MOSQUITO
6. gametocytes ingested by
mosquito.
7. Male and female gametes
HUMAN HOST fuse. Zygote oocyst in
2. Sporozoites infect liver cells. Multiply stomach wall.
by schizogony. 8. Sporozoites form in oocyst.
Note: some sporozoites of P.vivax and 9. Oocyst ruptures.
p.ovale become dormant hypnozoites Sporozoites reach salivary
in liver. Become active after several glands of mosquito
months.
3. Liver schizonts rupture. Merozoites
enter red cells, become trophozites.
Multiply by schizogony.*
* with P. falciparum, schizogony
occurs in capillaries of body organs.
4. Schizonts rupture. Merozoites infect
new red cells.
5. Some merozoites develop into male
and female gametocytes.
Fig. 5.1 Transmission and life cycle of Malaria parasites. (From Monica
96
Chills, rigor, fever, head ache, diarrhea, hallucinations,
abdominal pain, aches, renal or respiratory symptoms,
jaundice, etc.
Diagnosis
Clinical manifestation and epidemiological grounds
Blood film for hemoparasite
White blood cell count
Blood culture to rule out sepsis
Chest X-ray to rule out pneumonia.
Treatment
1. Plasmodium vivax, ovale and sensitive plasmodium
falciparum
Chloroquine or
Fansidar
2. Chloroquine resistant falciparum and when sensitivity
pattern is not known.
Quinine or
Fansidar
Nursing care
1. Advise patient to come back if the illness gets severe.
2. Advise on personal protection (bed nets, etc).
3. Reduce fever and maintain comfort.
97

1. Chemoprophylaxis- for those who go to endemic areas
but not for those who live in the endemic area (travelers
and newcomers); for under-five children and pregnant
mothers who have not enough immunity.
2. Vector control
Avoiding mosquito breeding sites
Residual DDT spray or other chemicals
Personal protection against mosquito bite (use of bed
nets, etc.)
3. Chemotherapy of cases
5.3.2 Bancroftian filariasis
Definition
A disease caused by the reaction of the body to the presence
of worms in the lymphatic system.
Infectious agent
Wucheriria bancrofti (vectors are culex, Anopheles and Aedes
species)
Brugia malayi and (vector is mansonia species)
Brugia timori (vector is Anopheles)
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Epidemiology
Occurrence- Widely prevalent in tropical and subtropical
areas of Africa, Asia, Pacific Region, Central and South
America. Found in Gambella region (western Ethiopia).
Reservoir- Humans are definitive hosts.
Mode of transmission- by bite of mosquito harboring

infective larvae
Incubation period- one month, while allergic inflammatory

manifestations may appear.
Period of communicability- Humans may infect mosquitoes

when microfilariae are present in the peripheral blood.
Microfilaremia may persists for 5-10 years or longer. The
mosquito becomes infective about 12-14 days after an
infective blood meal.
Susceptibility and resistance- Universal. Susceptibility to

infection is probable.
99
Life cycle
TRANSMISSION
1. Infective larvae penetrate skin
when a mosquito takes a blood
meal.
MOSQUITO
4. Microfilariae ingested by
mosquito.
5. Microfilariae lose sheath.
Develop into infective larvae
in thoracic muscles.
HUMAN HOST* 6. Infective larvae (sheathed)
2.Larvae become adult worms migrate to mouth parts.
in the lymphatics.
3. Females produce sheathed
Microfilariae which pass into
blood.
* Animal hosts may be important for
B. Malayi.
Fig. 5.2 Transmission and life cycle of W. bancrofti and Brugia species (From
Monica Chesbrough, 1998, District Laboratory Practice in Tropical Countries,
Part One, Cambridge University Press, London.)
The presence of worms in the lymph vessels gives rise to a
foreign-body reaction. After the death of the worm, more
proteins are released; the reaction then is even more severe.
Three phases may be distinguished.
Acute phase:
Starts within a few months after infection
Lymphadenopathy
Fever
100
Eosinophilia
In this stage microfilariae are not demonstrable in the
peripheral blood because the worms are not yet mature.
The acute phase is mainly due to a hypersensitivity
reaction.
Subacute phase:
This occurs after about one year following acute phases.
In this phase worms have matured and micro filariae are
present in the peripheral blood.
Reactions to the adult worms cause attacks of fever with
lymphangitis, funiculitis or Epididymitis. Recurrent attacks
will sooner or later lead to hydrocele.
Lesions caused by microfilariae are less common and are
associated with hypereosinophilia and lung symptoms
(tropical pulmonary eosinophilia syndrome).
Chronic phase:
After many years of repeated attacks, lymph glands and
lymph vessels become obstructed; as a result lymph
edema develops. Lymph edema most commonly seen in
the legs or scrotum (elephantiasis) but may also be
present in vulva, breasts, or arms.
Since the adult worms have usually died, microfilariae are
not seen in the blood.
101
N:B Studies showed that elephantiasis of the lower legs is not

encountered in Ethiopia. But there is elephantiasis of the foot
called the big foot disease (elephantiasis of lower leg) as a
result of accumulation of silica and other minerals in the leg
(lymphatics) mostly occurring in bare-footed individuals. This
big foot disease is named podoconiosis, which is common in
the eastern high lands of Ethiopia (Wolayita, Gojjam, Gondar,
Gedeo, Sidamo, etc.).
Diagnosis
Clinical and epidemiological grounds
Obstructive signs with history and travel to and
residence in endemic areas.
Best established by identifying microfilariae in the
peripheral blood (blood film).
Before taking blood sample one should know the
periodicity of microfilariae. That is, microfilariae appear in
the peripheral blood during the night (nocturnal) in most
parts of the world and during day (diurnal) in the South
Pacific region.
Single dose of Diethylcarbamazin Citrate (DEC) causes
the sequestered microfilariae to emerge to blood 45-60
minutes later. This test is said to be the mazoti test, which
is used in nocturnal periodicity.
102
Treatment
1. Diethyl carbamazin Citrate (DEC) results in rapid
disappearance of most microfilariae from blood but may
not destroy the adult worm. Because of this, we need to
repeat DEC annually for some years.
2. Refer the patient for surgical treatment of hydrocele.

1. Reducing the vector population
2. Mass and selective treatment
3. Personal protection against mosquito bite.
5.3.3 Yellow fever
Definition
An acute infectious viral disease of short duration and varying
severity.
Infectious agent
Yellow fever virus
Epidemiology
Occurrence- The disease exists in two transmission cycles.
Namely, the sylvatic or Jungle cycle, which occurs between
mosquitoes and non-human primates, and an urban cycle,
103
involving Aedes aegypti mosquitoes and humans. Found in

southwest Ethiopia (Gambella region).
Reservoir- Urban areas- humans and Aedes aegypti

mosquitoes. Forest areas- Vertebrates other than humans
(mainly monkeys) and forest mosquitoes.
Mode of transmission- By the bite of infective Aedes aegypti

mosquitoes
Incubation period- 3-6 days
Period of communicability- Blood of patients is infective for

mosquitoes shortly before onset of fever and for the first 3-5
days of illness. Not communicable by contact or common
vehicles. The disease is highly communicable where many
susceptible people and abundant vector mosquitoes co-exist.
Susceptibility and resistance- Recovery from yellow fever is

followed by lasting immunity; second attacks are unknown.
Transient passive immunity in infants born to immune mothers
may persist for up to 6 months. In natural infections,
antibodies appear in the blood within the first week.
104
Typical attacks are characterized by sudden onset of
fever, chills, headache, backache, generalized pain,
prostration, nausea and vomiting.
Slow and weak pulse.
Bleeding tendency is common resulting in epistaxis,
bleeding of gums, hematemesis, melaena.
Jaundice occurs due to liver cell necrosis and this may
result in liver failure and death.
Albumin uria occurs due to nephrosis and this may result
in kidney failure and anuria.
Patients surviving the seventh day of the disease usually
recover.
Diagnosis
History of residence and/or travel to endemic area
Treatment
No specific treatment.
Nursing care
1. Monitor vital signs regularly.
3. Monitor input and output balance.
4. Keep patient in screened rooms or under mosquito nets to
avoid further infection.
105

1. Active immunization of all people greater than 9 months of
age necessarily exposed to infection because of
residence, occupation or travel.
2. Eradication or control of Aedes aegypti mosquitoes in
urban areas.
3. Sylvatic /Jungle yellow fever- immunization to all people in
rural communities whose occupation brings them into
forests in yellow fever areas and for people who visit
those areas.
4. Notification of the disease to the concerned health
authorities.
5.4 Flea-Borne Diseases
5.4.1. Plague
Definition
A highly infectious bacterial disease which can kill many
people within a short time.
Infectious agent
Yersinia pestis, the plague bacillus.
Epidemiology
Occurrence- Endemic in wild rodents living in forests in the
highlands. Wild rodent plague exists in western USA, large
106
areas of South America, North, Central, Eastern and Southern

Africa, Central and Southeast Asia. However, urban plague is
controlled in most of the world.
Reservoir- Wild rodents (especially ground squirrels) are the

natural vertebrate reservoir of plague. Wild carnivores and
domestic cats may also be a source of infection to people.
Mode of transmission- Through the bite of infected fleas.

Handling of tissues of infected animals.
Incubation period- 1-7 days.
Period of communicability- Fleas may remain infective for

months under suitable conditions of temperature and
humidity. Bubonic plague is not usually transmitted directly
from person to person unless there is contact with pus from
suppurating buboes. Pneumonic plague may be highly
communicable under appropriate climatic conditions.
Overcrowding facilitates transmission.

Immunity after recovery is relative; it may not protect against a
large inoculums.
107
Bubonic plague- Characterized by swelling of lymph glands
(bubos); mostly the glands of the groins, sometimes arm pit or
other places. Swelling may be the size of an egg, tender or
non-tender. Other symptoms are:
Sudden high fever
Shock
Prostration
Coma
Death within 3-5 days
Pneumonic plague
Acute onset
Severe prostration
Watery sputum quickly followed by blood-stained sputum.
Pleural effusion
Death within 1-2 days
Diagnosis
Gram stain of sputum or pus-gram negative bacilli.
Treatment
1. Early treatment with antibiotics like streptomycin or
tetracycline or sulfa groups.
108

1. Chemotherapy of patient
2. Chemoprophylaxis of all contacts with Sulfa drugs
3. The area where disease occurs must be quarantined
(isolated from outer world)
4. Insecticides to kill fleas
5. Encourage people to kill rats
6. Notify the disease to the concerned health authority.
5.4.2 Endemic Typhus (Flea-borne typhus)
Definition
A rickettsial disease whose course resembles that of louse-
borne typhus, but is milder.
Infectious agent
Rickettsia typhi (Rickettsia mooseri)
Epidemiology
Occurrence- Worldwide, found in areas where people and
rats occupy the same buildings and where large numbers of
mice live. Occurs sporadically.
Reservoir-Rats, mice and possibly other small animals.

Infection is maintained in nature by a rat-flea-rat cycle where
rats are reservoirs (Commonly rattus and rattus novergicus).
109
Mode of Transmission- Infective rat fleas defecate rickettsia

while sucking blood, contaminating the bite site and other
fresh skin wounds. An occasional case may follow inhalation
of dried infective flea feces.
Incubation period- from 1 to 2 weeks; commonly 12 days
Period of communicability- Not directly transmitted from

person to person. Once infected, fleas remain so for life.

One attack confers immunity.
Prodromal symptoms of headache, myalgia, arthralgia,
nausea, and malaise developing 1 to 3 days before the
abrupt onset of chills and fever. Nearly all patients
experience nausea and vomiting early in the illness.
The duration of untreated illness averages 12 days.
Rash is present in only 13% of patients
Pulmonary involvement: non-productive cough and
pneumonia.
Diagnosis
Epidemiological ground
Weilfelix agglutination test (Serology)
110
Treatment
1. Doxycyclin or
2. Chloramphenicol

1. Destroy rats from burrows and harborages.
2. Use insecticides to abolish flea from livingquarters.
3. Treatment of patients.
5.5 Louse-Borne Diseases
5.5.1 Epidemic Typhus
Definition
An acute rickettsial disease often with sudden onset.
Infectious agent
Rickettsia Prowazeki
Epidemiology
Occurrence- In colder areas where people may live under
unhygienic conditions and are louse-infected. Occurs
sporadically or in major epidemics, for example during wars or
famine, when personal hygiene deteriorates and body lice
flourish.
111
Reservoir- Humans. Infected lice die and don’t serve as a

reservoir.
Mode of transmission- The body louse and head louse are

infected by feeding on the blood of a patient with acute typhus
fever. Infected lice excrete rickettsiae in their feces and
usually defecate at the time of feeding. People are infected by
rubbing feces or crushed lice into the bite or into superficial
abrasions (scratch inoculation).
Incubation period- From 1 to 2 weeks, commonly 12 days
Period of communicability- Patients are infective for lice

during febrile illness and possibly for 2-3 days after the
temperature returns to normal. Infected lice pass rickettsiae in
their feces within 2-6 days after the blood meal; it is infective
earlier if crushed. The louse die within 2 weeks after infection.
Rickettsiae may remain viable in the dead louse for weeks.

One attack usually confers long-lasting immunity.
Early symptoms of fever, headache, mayalgia, macular
eruption appear on the body.
112
Patient may have pneumonia, renal or CNS involvement,

gastrointestinal disease, skin rash singly or in
combination.
Disease usually terminates by rapid lysis after 2 weeks of
fever.
Diagnosis
Based on clinical and epidemiologic grounds
Serologic test (weil-felix agglutination test)
Treatment
1. Chloramphenicol or Tetracycline

1. Delousing of clothes by insecticides or dipping into boiling
water
2. Public education on personal hygiene
4. Chemoprophylaxis for contacts.
5.5.2 Relapsing Fever
Definition
An acute infectious bacterial disease characterized by
alternating febrile periods (recurrent pyrexial attacks).
113
Infectious agent
Borrelia recurrentis- cause of louse-borne relapsing fever
Borrelia duttoni-cause of tick-borne relapsing fever
Epidemiology
Occurrence- Occurs in Asia, eastern Africa (Ethiopia and
Sudan), the highland areas of central Africa and South
America. It occurs in epidemic form when it is spread by lice
and in endemic form when spread by ticks.
Reservoir- Humans for Borrelia recurrentis; , wild rodents and

soft ticks through transovarian transmission. for tick borne
relapsing fever
Mode of transmission- vector-borne. Acquired by crushing

an infected louse so that it contaminates the bite wound or an
abrasion of the skin.
Incubation period- 5-10 days usually 8 days.
Period of communicability- Louse becomes infective 4-5

days after ingestion of blood from an infected person and
remains so for life (20-40 days)
114

Duration and degree of immunity after clinical attack are
unknown; repeated infection may occur.
Sudden onset of illness with chills, fever and prostration,
headache, mayalgia and arthralgia
There may be nausea and vomiting, jaundice and liver
swelling.
After 4-5 days the temperature comes down, the patient stays
free for 8-12 days and then a relapse follows with the same
signs but less intense.
In untreated cases there may be up to ten relapses.
Diagnosis
Clinical and epidemiological grounds
Giemsa or Wright stain (blood film)
Dark field microscopy of fresh blood.
Treatment
1. Admit the patient.
2. Open vein (i.e. start iv-line) before administering penicillin.
3. Administer 400,000-600,000 IU procaine penicillin IM stat
4. Tetracycline during discharge for 3 days
5. Chloramphenicol in infants and children can be used in
place of tetracycline.
115
Nursing care
2. Close vital sign monitoring for 3 hours after medication.
3. Check whether there is reaction or not and report.
4. Comfort the patient by providing antipain.
5. Shaving of hair, and delousing of clothes.

1. Control of vectors (louse)
2. Personal hygiene
3. Health education about hygiene and modes of disease
transmission
4. Delousing of patient’s clothes and his/her family
5. Chemotherapy of cases and Chemoprophylaxis for
contacts.
5.6 Snail-Borne Diseases
5.6.1 Schistosomiasis
Definition
It is a blood fluke (trematode) infection with adult worms living
within mesenteric or vesicle veins of the host over a life span
of many years.
116
Infectious agent
The major schistoma species that cause schistosomiasis of
humans are:
Schistosoma mansoni
Schistosoma Japonicum
Schistosoma Hematobium
Others in limited areas are S. mekongi, S. intercalatum, S.

malayesis, S. mattheei.
Most prevalent species in Africa are S. mansoni and S.

hematobium.
Snail vectors are:

Bulinus-S. hematobium
Biomphalaria-S. mansoni
Onchomelania-S. japonicum
Epidemiology
Occurrence- S. mansoni is found in South America,

Caribbean Islands, Africa and the Middle East. S. hematobium
is found in Africa and the Middle East. S. Japonicum is found
in the Far East. The disease occurs worldwide and 2 million
people are expected to be infected; however, most infected
individuals show few or no signs and symptoms, and only a
small minority develop significant disease.
117
Reservoir-The principal reservoir for S. mansoni, S.

hematobium and S. intercalatum is man. Other animals, like
dog, cat, pig, cattle, water buffalo, horse and wild rodents, are
hosts for S. japonicum.
Mode of transmission-Infection is acquired from water

containing free-swimming larval forms (cercariae) that have
developed in snails.
Incubation period-Acute systemic manifestations (katayama

fever) may occur in primary infections 2-6 weeks after
exposure, immediately before and during initial egg
deposition. The infection in humans can persist up to 10
years. Snails release cercariae as long as they live (from
several weeks to 3 months).
Susceptibility and resistance-Susceptibility is universal.

Resistance is poorly defined.
118
Life cycle
TRANSMISSION
1. Cercariae penetrate skin when
person in contact with contaminated
water
FRESH WATER
7. Eggs reach water.
Miracidia hatch
Snail host
8. Miracidia penetrate snail.
HUMAN HOST*
Become sporocysts and
2. Cercariae Î Schistosomula.
multiply (2 generations).
Migrate through lungs and
Sporocysts Î cercariae.
liver.
9. Cercariae leave snail.
3. Become mature flukes in
(S.Japonicum attaches to
portal venous system. Flukes
water vegetation).
pair.
4. Migrate to veins of lower large
intestine (S. haematobium to
veins of bladder)
5. Eggs laid in venules. Burrow
through into intestine (eggs of
S. haematobium into bladder)
6. Eggs passed in feces. (S.
haematobium in urine).
*S. japonicum also infects animals.
Fig. 5.3 Transmission and life cycle of Schistosoma species. (From Monica
The stages of schistosomiasis are:
A. invasion
B. maturation
C. established infection and
D. late stage.
119
A. Invasion stage
Cercariae penetrate skin
Cercarial dermatitis with itching papules and local edema
Cercariae remain in skin for 5 days before they enter the
lymphatic system and reach the liver.
B. Maturation
Schistosoma mature in the liver.
Fever, eosinophilia, abdominal pain and transient
generalized urticaria (known as katayama syndrome)
Worms descend the portal vein. S. manson; migrates to
mesenteric veins in the intestinal wall and S.
haematobium to bladder plexus.
This stage may be diagnosed as clinical malaria or may
pass unnoticed.
C. Established infection
This is a stage of egg production and eggs reach to the
lumen of bladder and bowel.
Some eggs penetrate the tissue, reach the bladder and
intestinal wall are discharged with urine and feces.
Eggs that could not penetrate the tissue are carried with
blood to the liver and lungs.
Other eggs that fail to reach the lumen of the bladder or
bowel provoke an inflammatory reaction.
120
The inflammatory reaction, resulting in fibrosis, causes

signs and symptoms of schistosomiasis.
Sign of colitis with bloody diarrhea and cramps in S.
mansoni infection. Terminal haematuria and dysuria in S.
haematobium infection.
D. Late stage
This is the stage of fibrosis, which occurs where there are
eggs in the tissues. Around the bladder this may result in:
- Stricture of urethra leading to urine retention or fistula.
- Dilatation of ureters (hydroureter) and kidney
(hydronephrosis) possibly leading to kidney failure
- Calcification of bladder.
In the liver portal hypertension leads to hypersplenism

and anemia, eosophageal varices and bleeding.
In the lungs fibrosis results in pulmonary hypertension,
which leads to congestive cardiac failure.
Diagnosis
Demonstration of ova in urine or feces,
Biopsy of urine and feces are repeatedly negative (rectal
snip, liver biopsy, bladder biopsy).
Treatment
121
Praziquantel and oxamniquine are the drugs of choice but in

Africa praziquantel is best because of resistance strain of
oxamniquine.

2. Intermittent irrigation
3. Drainage of water bodies
4. Clearing of vegetation in water bodies to deprive snails of
food and resting place
5. Flooding
6. Straightening and deepening margins of water bodies
7. Educating the public about the mode of transmission and
ways of prevention
8. Proper disposal of human feces and urine
9. Avoid swimming in water bodies known to have the
infection
10. Use rubber boots to prevent exposure to contaminated
water.
5.6.2 Guinea Worm Infection
Definition
An infection of the subcutaneous and deeper tissues by large
nematode.
122
Infections agent
Dracunculus medinensis, a nematode
Epidemiology
Occurrence- In Africa (16 countries south of the Sahara) and
in Asia (India and Yemen) especially in regions with dry
climates. Local prevalence varies greatly. In some locales,
nearly all inhabitants are infected, in others, few, mainly young
adults.
Reservoir- Humans
Mode of transmission- Larvae discharged by the female

worm into stagnant fresh water are ingested by minute
crustacean copepods (Cyclops species). In about 2 weeks,
the larvae develop into the infective stage. People swallow
the infected copepods in drinking water from infested step-
wells and ponds. The larvae are liberated in the stomach,
cross the duodenal wall, migrate through the viscera and
become adults. The female, after mating, grows and develops
to full maturity, then migrates to the subcutaneous tissues
(most frequently of the legs).
Incubation period- About 12 months
123
Period of communicability- From rupture of vesicle until

larvae have been completely evacuated from the uterus of the
gravid worm, usually 2-3 weeks. In water, the larvae are
infective for the copepods for about 5 days. After ingestion by
copepods, the larvae become infective for people after 12-14
days at temperatures >25c0 and remain infective in the
copepods for about 3 weeks.
Susceptibility and resistance- Susceptibility is universal. No

acquired immunity; multiple and repeated infections may
occur in the same person.
Few or no clinical manifestations are evident until just
before the blister forms.
Fever and generalized allergic symptoms, including
periorbital edema, wheezing, and urticaria.
The emergence of the worm is associated with local pain
and swelling.
When the blister ruptures, the adult worm releases larva-
rich fluid and this is associated with a relief of symptoms.
The shallow ulcer surrounding the emerging adult worm
heals over weeks to months.
Diagnosis
124
Treatment
1. Gradual extraction of the worm by winding of a few
centimeters on a stick each day remains the common and
effective practice. Worms may be excised surgically.
2. Administration of thiabendazole or metronidazol may
relive symptoms but has no proven activity against the
worm.

1. Provide health education programs in endemic
communities to covey three messages:
The guinea-worm infection comes from their drinking
water
Villagers with blisters or ulcers should not enter any
source of drinking water and
That drinking water should be filtered through fine
mesh cloth to remove copepods
2. Provision of safe drinking water
125
Review Questions
1. What do you understand by vector-borne disease

transmission?
2. Which of the vector-borne diseases pose major health
problems in Ethiopia?
3. Except one, others do not require notification to the health
authorities
a) Malaria
b) Yellow fever
c) Plague
d) B and C
e) Schistosomiasis
4. What are the preventive and control methods for malaria
and schistosomiasis?
126
CHAPTER SIX
SEXUALLY TRANSMITTED
DISEASES

List the common sexually transmitted diseases (STDs).
Identify the diagnostic symptoms of sexually transmitted
diseases.
Identify sexually transmitted diseases that are transmitted
through vertical route.
Apply the management of sexually transmitted diseases.
State the preventive and control measures for sexually
transmitted diseases.
6.2. Introduction
The diseases belonging to this group are usually transmitted

during sexual intercourse; hence the name sexually
transmitted diseases or STDs. During sexual intercourse there
is close body contact, which is an ideal situation for
127
transmission. The causative organisms of the STDs are very

easily killed by drying or by cooling to below body
temperature. Therefore transmission of these agents from one
person to another can only occur under very special
circumstances, mostly during sexual intercourse. STDs are
very common in adults, but they are often hidden for fear of
the opinion of others. Single young men are a high–risk group
for STDs, as they satisfy their sexual needs with women who
have many sexual partners (promiscuity). They may be
professional prostitutes, barmaids, or persons who in other
ways gain from casual sexual relationships. This group is
called the promiscuous women pool (PWP). They are the
reservoir of STDs.
Risk factors are:

1. Age: 15 years and older
2. Marital status: unmarried people who often change their
sexual partners are more frequently exposed. Most of the
women in the PWP are unmarried or divorced.
3. Occupation: soldiers, policemen, students, seasonal
laborers, and other people who are temporarily away from
home tend to expose themselves more easily.
4. Residence: Due to industrialization and consequent
urbanization there is usually a large group of single young
men in towns. Women in towns may have more difficulty
128
in earning their daily living than women in rural areas and

may take up prostitution for money.
5. Promiscuity
6.3 Syphilis (Hard chancre)
Definition
A disease characterized by a primary lesion, a later
secondary eruption on the skin and mucus membranes, then
a long period of latency, and finally late lesions of skin, bones,
viscera, CNS and cardiovascular systems.
Infectious agent
Treponema pallidum, a spirochete.
Epidemiology
Occurrence: Worldwide spread. Primarily involving sexually
active young people between 20 and 29 years. More common
in urban than rural areas.
Reservoir - Humans
Mode of transmission:- by direct contact with lesion mainly

during sexual intercourse. Accidentally by touching infective
tissues. Or via blood transfusion. Or congenitally, which may
occur before birth, in the case of an infected mother.
129
Incubation period– 10 days to 3 months, usually 3 weeks.
Period of communicability – variable and indefinite, during

primary and secondary stages and also in mucocutaneous
recurrences that may occur during the first 4 years of latency.
Extent of communicability through sexual activity during this
latent period is not established. Adequate penicillin treatment
usually ends infectivity within 24 – 48 hours.
Susceptibility and resistance – Susceptibility is universal,

although only approximately 30% of exposures result in
infection. Infection leads to developing immunity against T.
pallidum gradually and to some extent, but immunity usually
fails to develop because of early treatment in the primary and
secondary stages.
The clinical presentation is divided into three groups:
a) Primary syphilis – consists of hard chancre, the primary
lesion of syphilis, together with regional lymphadenitis.
The hard chancre is a single, painless ulcer on the
genitalia or elsewhere (lips, tongue, breasts) and heals
spontaneously in a few weeks without treatment.
The lymph glands are bilaterally enlarged and not painful.

There will not be suppuration.
130
b) Secondary syphilis - After 4 – 6 weeks of the primary

infection, a generalized secondary eruption appears, often
accompanied by mild constitutional symptoms. These
early rashes tend to be symmetrical, quickly passing, and
do not itch. These early skin lesions are highly infective
and many spirochetes are demonstrated in them.
c) Tertiary syphilis -This stage is characterized by
destructive, non-infectious lesions of the skin, bones,
viscera, and mucosal surfaces. Other disabling
manifestations occur in the cardiovascular system (aortic
incompetence, aneurysms) or central nervous system
(dementia paralytica, tabes dorsalis).
d) Syphilis in pregnancy- According to the severity,
congenital syphilis can result in congenital abnormalities,
still birth, or repeated spontaneous abortions.
Diagnosis
Serological test – will be positive 6 to 8 weeks after
infection
Dark field microscopy of smears from primary lesion
(hard chancre) or from skin lesions in the early secondary
stage will show the spirochaetes.
131
Treatment
1. Primary and secondary syphilis
Benzathin penicillin 2.4 M IU Im stat or
Tetracycline or Erythromycin 500mg PO Qid for 2
weeks for penicillin sensitive people
2. Tertiary syphilis
Benzathin penicillin 2.4 M IU Im single dose every
week for 3 consecutive weeks or
Tetracycline or Erythromycin for one month for
penicillin sensitive individuals.
3. Early congenital syphilis

Crystalline penicillin 50,000 IU/ Kg per dose IV or Im
bid in the first 7 days of life and Tid then after for 10-
14 days.

2. Treatment of contacts and source of infection
3. Health education on safe sex
4. Controlling STDs among commercial sex workers
Monthly check up and treatment of cases
Provision of condom
5. Screening of pregnant women and early treatment to
prevent congenital syphilis
6. Screening of blood before transfusion.
132
6.4 Chancroid (soft chancre)
Definition
An acute bacteria infection localized in the genital area and
characterized clinically by single or multiple painful narcotizing
ulcers at the site of infection.
Infectious agent.
Haemophilus ducreyi, the Ducrey bacillus
Epidemiology
Occurrence – endemic in many developing countries. The
commonest cause of genital ulcer in many developing
counties. Most frequently diagnosed in men, especially those
who frequently prostitutes.
Reservoir – Humans
Mode of transmission – by direct sexual contact with

discharges from open lesion and pus from buboes. Infected
males don’t pass the infection farther because of the painful
ulcer.
Incubation period – from 3 to 5 days, up to 14 days after

sexual contact.
Period of communicability – until healed and as long as the

infectious agent persists in the original lesion or discharging
133
regional lymph nodes, which lasts for several weeks or

months without antibiotic treatment. Antibiotic therapy
eradicates H. ducreyi, and lesions heal in 1 – 2 weeks.
Susceptibility and resistance – Susceptibility is general.

The uncircumcised are at higher risk than the circumcised. No
evidence of natural resistance.
Classic Chancroid ulcer begins as a tender papule
that ulcerates within 24 hours.
The ulcer is painful, irregular and sharply demarcated
from the nearby skin.
About 50% of men will have single ulcer.
Diagnosis
Clinical, but always rule out syphilis
Gram stain of smear from ulcer shows typical rods in
chain
Culture.
Treatment
1. Co- trimorazele or
2. Erythromycin or
3. Tetracycline can be used
N.B. Do not incise lymph nodes even with fluctuation because
they will completely heal with treatment.
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1. Case treatment
2. Investigation of contacts, source of infection and
treatment
3. Thorough washing of genitalia with soap and water
promptly after intercourse is very effective.
4. Controlling STDs among commercial sex workers
5. Sex education for high risk groups
6.5 Lymphogranuloma venereum.
Definition
A venereal disease caused by chlamydia microorganisms,
most commonly manifested by acute inguinal lymph adenitis.
Infectious agent
Chlamydia trachomatis (Ll L2 and L3)
Epidemiology
Occurrence – Common in most parts of the world but very
common in tropical and subtropical regions of Africa and Asia.
Its incidence is more common in males than females, and is
lower than Gonorrhea and Chancroid.
Reservoir- Humans often asymptomatic (particularly in

females)
135
Mode of transmission- Direct contact with open lesions of

infected people, usually during sexual intercourse.
Incubation period – variable, with a range of 3 – 30 days for

a primary lesion.
Period of communicability – variable, from weeks to years,

during presence of active lesions.
Susceptibility and resistance – Susceptibility is general.

Status of natural or acquired resistance is unclear.
Lymph adenopathy with non-specific symptoms of fever,
chills, head ache, malaise, anorexia and weight loss.
Regional lymph nodes undergo suppuration followed by
extension of inflammatory process to the adjacent tissues.
In the female, inguinal nodes are less frequently affected
and involvement is mainly of the pelvic nodes with
extension to the rectum and recto vaginal septum,
resulting in proctitis, stricture of the rectum and fistula.
Elepthantiasis of genitalia, scrotum and vulva occur in
either sex.
Diagnosis
Clinical presentation (i.e. presence of bubo.)
Culture of bubo aspirate.
136
Treatment
1. Tetracycline or
2. Erythromycin or
3. Co -trimoxazole can be used
4. Aspiration of fluctuating bubo and wound care

1. Early diagnosis and treatment of cases
2. Investigation of contacts, source of infection and
treatment
3. Controll STDs among commercial sex workers
4. Sex education for high risk groups
6.6 Herpes Genitalia
Definition
A viral infection characterized by a localized primary lesion,
latency and a tendency to localized recurrence.
Infectious agent
Herpes simplex virus (HSv) type 2
Epidemiology
Occurrence – worldwide. HSV 2 infection usually begins with
sexual activity and is rare before adolescence, except in
sexually abused children. Prevalence is greater (up to 60%) in
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lower socio-economic groups and persons with multiple

sexual partners.
Reservoir – Humans.
Mode of transmission - Usually by sexual contact.

Transmission to the neonate usually occurs via the infected
birth canal, but less commonly occurs
intrauterine or postpartum
Incubation period – 2 – 12 Days
Period of communicability – Patients with primary genital

lesions are infective for about 7 –12 days, with recurrent
disease for 4 days to a week. Reactivation of genital herpes
may occur repeatedly in > 50% of women.
Susceptibility and resistance – Humans are universally

susceptible.
First – episode primary genital herpes is characterized by
fever, head ache, malaise and myalgias
Pain, itching, dysuria, vaginal and urethral discharge, and
tender inguinal lymph adenopthy are the predominant
local symptoms.
138
Widely-spaced bilateral lesions of the external genitalia

are characteristic: lesions may be vesicles, pustules, or
painful erythematous ulcers.
Cervix and urethra are involved in more than 80% of
women with first episode infection.
A clear mucoid discharge and dysuria are characteristics/
symptoms of urethritis.
Occasionally, HSV genital tract disease is manifested by
endometritis and salpingitis in women and by prostatitis in
men.
Treatment
1. Oral acyclovir is effective

1. Consistent use of condom is an effective means of
reducing the risk of genital HSv – 2 transmission.
6.7 Candidiasis
Definition
A mycosis usually confined to the superficial layers of skin or
mucus membranes, presenting clinically as oral thrush or
vulvovaginitis.
Infectious agent
Candida albicans (most common cause)
Candida tropicalis (rare cause)
139
Epidemiology
Occurrence – Worldwide. Candida albicans is often part of
the normal human flora.
Reservoirs – Humans
Mode of transmission – contact with secretions or excretions

of mouth, skin, vagina and feces, from patients or carriers.
Passage from mother to neonate during childbirth.
Incubation period – variable.
Period of communicability - presumably while lesions are

present.
Susceptibility and resistance – Susceptibility is very low

except in low host defense. It is common in diabetes, HIV-
infected; women are prone to vulvovaginitis in the third
trimester of pregnancy. Oral contraceptive users, individuals
with prolonged steroid therapy are susceptible.
Severe vulvar pruritis (prominent feature)
vaginal discharge (scanty, whitish, yellow, thick to form
curds, non-offensive)
sore vulva due to itching
speculum examination – thick whitish plugs attached to
vaginal wall
140
vaginal epithlium bleeds when the plug is removed but the

cervix is normal
Diagnosis
Microscopic demonstration of pseudohyphae or yeast
cells in infected tissue or body fluids (vaginal discharge)
Culture (vaginal discharge)
Treatment
1. Nystatine vaginal pessary or
2. Miconazole or clotrmazele creams or
3. Keto conazole or
4. Fluconazele in recurrent cases

1. Case treatment
2. Treatment of underlying medical conditions or predisposing
factors
6.8 Gonorrhea
Definition
An acute or chronic purulent infection of the urogenital tract.
Infectious agent
Neisseria gonorrhea, the gonococcus
141
Epidemiology
Occurrence – worldwide, affecting both genders, especially
sexually active adolescents and young adults. Common in
rural areas. Prevalent in communities of lower socio-economic
status. In most industrialized countries, the incidence has
decreased during the past two decades.
Reservoir - Strictly a human disease
Mode of transmission - almost always as a result of sexual

activity
Incubation period - usually 2-7 days
Period of communicability - may extend for months in

untreated individuals. Effective therapy ends communicability
within hours.
Susceptibility and resistance - Susceptibility is general. No

immunity following infection and reinfection is common.
Males- Usually involves the urethra resulting in purulent
discharge, dysurea and frequency.
Females - Females are usually asymptomatic. Vaginal

discharge is common. Most common site of infection is
cervix, followed by urethra, anal canal and pharynx.
Bartholinitis occurs unilaterally. Salpingitis as a complication
142
occurs in 20% of women. Neonates borne to infected mothers

develop a purulent discharge which exudes from between
eyelids which are edematous and erythematous 2 -3 days
postpartum.
Diagnosis
Gram stain of discharge (urethral, cervical, conjuctival
discharge)
Culture on selective media
Treatment
1. Co - trimoxazole or
2. Erythromycin or
3. Ceftriaxone can be used

1. The same as syphilis
2. Application of 1% tetracycline in both eyes of newborne
as soon as delivered.
6.9 Trichomoniasis
Definition
A common and persistent protozoal disease of the genito-
urinary tract.
Infectious agent
Trichomonas vaginalis, a flagellate protozoan
143
Epidemiology
Occurrence - worldwide spread, a frequent disease of all
continents and all races, primarily of adults, with the highest
incidence among females 16 - 35 years. Overall, about 20%
of females may become infected during their reproductive
years.
Reservoir - Humans.
Mode of transmission- by contact with vaginal and urethral

discharges of infected people during sexual intercourse.
Indirectly through contact with contaminated articles and
clothes.
Incubation period - 4 - 20 days, average 7days. Many are

symptom-free carriers for years.
Period of communicability - the duration of the persistent

infection, which may last for years.
Susceptibility and resistance -Infection is general, but

clinical disease is seen mainly in females.
Most men remain asymptomatic although some develop
arthritis, and a few have epididymitis or prostatitis.
144
Infection in women is usually symptomatic and manifests

with malodorous vaginal discharge often yellow, vulvar
erythema and itching dysuria or urinary frequency (in 30 -
50% of cases) and dyspareunia. These manifestations
don't clearly distinguish trichomoniasis from other types of
infections/vaginitis.
Diagnosis
Detection of motile trichomonads by microscopy of wet
mounts of vaginal or prostatic secretions remains the
conventional means of diagnosis.
Culture (most effective) takes 3 - 7 days.
Treatment.
1. Metronidazole or
2. Clotrimazole vaginal suppository for pregnant women
cures up to 50%.

1. case detection and treatment
2. condom use
3. Educate public to seek medical help whenever there is an
abnormal discharge from the genitalia and to refrain from
sexual intercourse until investigation and treatment of self
and partners are completed.
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6.10 HIV/AIDS
Definition
A severe, life - threatening clinical condition, first recognized
as a distinct syndrome in 1981. This syndrome represents the
late clinical stage of infection with the human immuno-
deficiency virus (HIV), which most often results in progressive
damage to the immune and other organ systems, including
the CNS.
Infections agent
Human immuno-deficiency virus (HIV) (HIV-1 and HIV-2 )
Epidemiology
Occurrence - worldwide spread pandemic. HIV -1 infections
are now distributed worldwide, but are most prevalent in Sub-
Saharan Africa, the Americas, western Europe and southern
and Southeast Asia. HIV -2 has been found primarily in West
Africa, with some cases in the western hemisphere and other
African countries that are linked epidemiological to West
Africa.
The MOH 2002 report depicts the following about the

HIV/AIDS situation in Ethiopia:
- The HIV prevalence rate for the country as a whole is
estimated at 6.66 percent.
146
- The estimated HIV prevalence rate for urban areas is 13.7

percent
- Prevalence rates for some urban centers other than Addis
Ababa are much higher than the rate for Addis Ababa.
- The estimated rural prevalence rate is 3.7 percent, which
is 25 percent of Addis Ababa’s rate.
- HIV seems to be driving the TB epidemic in Ethiopia.
- The highest prevalence of HIV is seen in the age group
15 to 24.
The figure is worrying as it represents “recent” infections.

Among the top ten leading causes of deaths, AIDS ranked 9th
with 0.8% in 1993 E.C.
Reservoir - Humans
Mode of transmission – Mainly through sexual exposure and

exposure to blood or tissues . Moreover, transplacental
transmission from an infected mother to the fetus.
Incubation period- variable. Although the time from infection

to the development of detectable antibodies is generally 1-3
months, the time from HIV infection to diagnosis of AIDS has
an observed range of less than 1year to 10years or longer.
About half of infected adults will have developed AIDS within
10 years after infection.
147
Period of communicability - unknown. Presumed to begin

early after onset of HIV infection and extend throughout life.
Susceptibility and resistance - unknown, but susceptibility

presumed to be general. Susceptibility is increased in the
presence of other STDs, especially those with ulcerations.
Acute HIV syndrome. Occurs 3 - 6 weeks after primary
infection. Clinical findings in the acute syndrome are: fever,
pharyngitis, lymphadenopathy, head ache, retro-orbital pain,
arthralgias, myalgias, lethargy or malaise, anorexia, weight
loss, nausea or vomiting or diarrhea. Meningitis, Encephalitis,
peripheral neuropathy, myopathy, erythematous
maculopupular rash, mucocutaneous ulceration.
Late complications of HIV infection

These result from opportunistic infections like pneumocystis
carinii pneumonia, Tuberculosis, cryptococcal meningitis, etc.
Diagnosis
Based on clinical ground in the late stage
Based on serologic test in the early and late stage
148
Treatment
1. No specific treatment.
2. Treatment of opportunistic infections.
3. Use of anti-HIV drug to reduce transmission of the virus to
the fetus of pregnant mothers reduces fetal infection.

1. prevention and control methods for other STDs
149
Review Questions
1. What are the common sexually transmitted infections?

2. What is the basic difference in the clinical manifestation of
syphilis, Chancroid and Herpes genitalia?
3. What are the common preventive and control methods
applicable to all STIs?
150
CHAPTER SEVEN
ZOONOTIC DISEASES

Define what zoonotic disease means.
Identify common modes of transmission for each disease.
Describe the clinical manifestations of each disease.
Participate in diagnosis and treatment of these diseases.
Implement preventive and control methods.
7.2 Introduction
Infectious diseases transmitted under natural conditions

between vertebrate animals and man are called zoonosis.
For most of these diseases, man is a dead-end of the
transmission cycle. This means under normal conditions, man
will not infect other human beings.
151
7.3 Food of Animals
7.3.1Taeniasis
Definition
Taeniasis is an intestinal infection with the adult stage of large
tapeworms. Cysticercosis is a tissue infection with the larval
stage.
Infectious agent
Taenia saginata (beef tapeworm)
Taenia solium (pork tapeworm)
Epidemiology
Occurrence- Worldwide; frequent where beef or pork is eaten
raw or insufficiently cooked and where sanitary conditions
permit pigs and cattle to have access to human feces.
Prevalent in Latin America, Africa, South East Asia and
Eastern Europe.
Reservoir- Humans are definitive hosts of both species of

Taenia; cattle are the intermediate hosts for Taenia saginata
and pigs for Taenia solium.
Mode of transmission- Eggs of Taenia saginata passed in

the stool of an infected person are infectious only to cattle in
the flesh of which the parasites develop into “cysticercus
152
bovis”; the larva stage of Taenia saginata. In humans,

infection follows after ingestion of raw or under-cooked beef
containing cysticerci; the adult worm develops in the intestine.
Taenia Solium eggs to mouth of oneself or to another person
or ingestion of food or water infected with eggs-embryos
escape from the shells-penetrate the intestinal wall lymphatics
or blood vessels and are carried to the various tissues where
they develop to produce the human disease of cysticercosis.
Incubation period- 8-14 weeks, eggs appear in stool in both

species.
Period of communicability- T. saginata is not directly

transmitted from person to person but T. solium may be. Eggs
of both species are disseminated into the environment as long
as the worm remains in the intestine, sometimes more than 30
years. Eggs may remain viable in the environment for
months.
Susceptibility and resistance- Susceptibility is general. No

apparent resistance follows infection but more than one
tapeworm in a person has rarely been reported.
153
Life cycle
TRANSMISSION
1. Cysticerci ingested in
undercooked meat. T. saginata
in beef T. solium in pork.
ENVIRONMENT
6. Segments and eggs reach ground
where animals feed.
Animal host:
Cattle for T. saginata pig for T. solium
7. Eggs ingested.
8. Embryos carried to muscles. Develop
into infective cysticerci.
HUMAN HOST
2. Cysticerci attached to wall of
small intestine.
3. Become mature tapeworms
4. Eggs released when gravid
segments become
detached.
5. Eggs and gravid segments
passed in feces.
Fig.7.1 Transmission and life cycle of Taenia solium and Taenia saginata.
(From Monica Chesbrough, 1998, District laboratory practice in tropical
countries, part one, Cambridge University press, London.)
Cysticercosis: Infection with T. solium larvae can occur by

ingesting eggs in food or from hands contaminated with feces.
Eggs develop into cysticerci causing cysticercosis and
neurocysticercosis.
154
Clinical manifestation (for both species)

Symptoms of cysticercosis may appear after some days
and stay for 10 years after infection.
Passage of proglottidis (segmented adult worms) in the
feces and perianal discomfort when proglottidis are
discharged.
Minimal or mild abdominal pain or discomfort, nausea,
change in appetite, weakness and weight loss.
Usually asymptomatic.
Epigastric discomfort, nausea, a sensation of hunger,
weight loss, nervousness, and anorexia.
Passage of proglottidis.
Diagnosis
Identification of proglottidis (segments)
Eggs in feces or anal swab
Cysticercus – palpable subcutaneous cysticercus and
microscopic examination of an excised cysticercus
confirms the diagnosis.
Intracerebral and other tissues- CT scan, MRI or by x-ray
when the cysticerci are calcified.
Treatment
1. Single dose of praziqantel is highly effective or
2. Niclosamide or
3. Dechlorophil or
155
4. Mebendazole or
5. Albendazole
T. Solium
Treatment is the same as to T. saginata but praziqantel
can evoke an inflammatory response in the CNS if cryptic
cysticercosis is present.
Cysticercosis management
- Chemotherapy
- Surgery and supportive medical treatment
For symptomatic patients with neurocysticercosis,
admission is required. Combination of Praziquantel and
Albendazole can be used. Besides, high dose of
glucocorticoids can be used to decrease inflammation.

1. Educate the public to:
Prevent fecal contamination of soil, water, human &
animal foods
Cook beef and pork thoroughly.
Use latrines.
2. Identification and immediate treatment of cases.
3. Freezing of pork/beef below –5co for more than 4 days
kills the cystraci effectively or cooking to a temperature of
56co for 5 minutes destroys cystcerci.
4. Deny swine access to latrines and human feces.
156
7.3.2 Brucellosis
Definition
A systemic bacterial disease with acute or insidious onset
transmitted to humans from infected animals.
Infectious agent
Brucella melitensis (most common worldwide), acquired
primarily from goats, sheep and camels.
B. abortus from cattle
B. suis from pigs
B. canis from dogs
These are small aerobic gram-negative bacilli, intracellular
parasites.
Epidemiology
Occurrence- Worldwide. Predominantly an occupational
disease of those working with infected animals or their tissues
especially farm workers, veterinarians and abattoir workers,
which is more frequent among males. Outbreaks can occur
among consumers of raw milk and milk products, especially
unpasteurized soft cheese from cows, sheep and goats.
Reservoir- cattle, swine, goats and sheep, pet dogs.
157
Mode of transmission- by contact with tissues, blood, urine,

vaginal discharges, aborted fetuses and especially placentas
(through breaks in the skin). Most commonly through
ingestion of raw milk and dairy products from infected animals
(raw meat or bone marrow). Airborne infection occurs in
humans in laboratories and abattoirs.
Incubation period- may last about 1-3 weeks but may be as

long as several months.
Period of communicability- no evidence of communicability

from person to person.
Susceptibility and resistance- Severity and duration of

clinical illness are subject to wide variation. Duration of
acquired immunity is uncertain.
Abrupt onset of symptoms
Most common symptoms are: Fever, chills, diaphoresis,
headache, myalgia, fatigue, anorexia, joint and low back
pain, weight loss, constipation, sore throat, and dry
cough.
Physical examination reveals
- Often no abnormalities and patient looks well
158
- Some are acutely ill, with pallor, lymphadenopathy,

hepatosplenomegally, arthritis, spinal tenderness,
epididymoorchitis, skin rash, meningitis, cardiac
murmurs, or pneumonia
- Reactive asymmetric polyartaritis (knees, hips,
shoulders, sacroiliac and sternoclavicular joints)
Diagnosis
Exposure and consistent clinical features
Serology- raised levels of B. agglutinin
Blood or bone marrow culture
Treatments
Doxycyline + aminogrycoside for 2 weeks followed by
Doxycycline + Rifampcin for 4-8 weeks is the most
effective regimen.
In pregnancy and in children less than 7 years, Bacterium
and Rifapcin for 8-12 weeks
N:B 4-14 days after the initiation of therapy, patients become
afebrile and constitutional symptoms disappear but enlarged
liver and spleen return to normal size within 2-4 weeks.

1. Control depends on elimination of the disease among
domestic animals.
159
2. Educate people not to drink untreated milk or eat products

made from untreated milk.
3. Educate farmers and slaughterhouse workers and those
in meat processing plants and butcher shops as to the
nature of the disease and the risk in the handling of
carcasses and products of potentially infected animals.
4. Educate hunters to use barrier precaution (gloves and
clothing).
5. Eliminate infected animals.
6. Pasteurize milk; cook meat and bone well.
7. Proper disposal of placenta, discharges or fetus from an
aborted animal. Disinfect contaminated areas.
7.3.3 Trichinellosis or Trichinosis
Definition
A disease caused by an intestinal round worm whose larvae
(trichinae) migrate to and become encapsulated in the
muscles.
Infectious agent
Trichinella spiralis, an intestinal nematode
Epidemiology
Occurrence - Worldwide, but variable incidence, depending
in part on practices of eating and preparing pork or wild
animal meat.
160
Reservoir - swine, dogs, cats, horses, rats and many wild

animals, including fox, wolf, etc.
Mode of transmission - By eating raw or insufficiently

cooked flesh of animals containing viable encysted larvae,
chiefly pork and pork products and "beef products" such
ashamburger adulterated either intentionally or inadvertently
with raw pork.
Incubation period - Systemic symptoms usually appear

about 8 - 15 days after ingestion of infected meat.
Susceptibility and resistance - Susceptibility is universal.

Infection results in partial immunity.
Symptoms result from invasion of the body by larvae
produced by the adult female worm in the intestine and
from their encystment in striated muscles.
Infection ranges from symptomatic to mild febrile illness to
a severe progressive illness with multiple system
involvement.
Fever (low - high grade)
Muscle pain mainly upon movement
Edema, and spasm (periorbital and facial)
Photophobia and conjunctivitis
161
Weakness or prostration
Pain on swallowing
Dyspnea, coughing and hoarseness
Subconjuctival, retinal and nail splinter hemorrhage and
rashes
Diarrhea
Abdominal cramps
Nausea and vomiting
Inflammatory reactions around larvae that reach tissues other

than muscles may result in:
Meningitis
Encephalitis
Myocarditis
Broncho-pneumonia
Nephritis
Peripheral and cranial nerve disorders
Diagnosis
History of ingestion of raw or inadequately cooked pork
Larvae in muscle biopsy
Positive serologic test
Eosinophilia
Treatment
1. Hospitalization of the patient
2. Mebendazole or
162
3. Albendazole or
4. Thiabendazole
5. High doses of corticosteroids for 1-2 days followed by
lower doses for several days or weeks. But not for
intestinal stage.

1. Educate the public on the need to cook all fresh pork and
pork products and meat from wild animals.
2. Freezing of pork and its products inactivates trichinae.
7.3.4 Toxoplasmosis
Definition
Toxoplasmosis is a systemic protozoal disease that can be
either acute or chronic type with intracellular parasite.
Toxoplasma gondii in which the parasite is responsible for the

development of clinically evident disease, including
lymphadenopathy, myocarditis and encephalitis.
Infectious agent
Toxoplasma gondii
163
Epidemiology
Occurrence- Worldwide in mammals and birds. Infection in
man is common. In the United States and most European
countries, the prevalence of sero-conversion increases with
age and exposure. In Central America, France, Turkey and
Brazil, sero-prevalence is much higher, approaching 90% by
age of 40.
Reservoir- The definitive hosts are cats and other felines,

which acquire the infection mainly from eating infected
mammals (especially rodents) or birds and rarely from feces
of infected cats. Only felines harbor the parasite in the
intestinal tract where the sexual stages of its life cycle takes
place, which result in the excretion of the oocyst in feces for
10-20 days or rarely longer. The intermediate hosts of T.
gondii include sheep, goats, rodents, cattle, chicken and birds.
Intermediate hosts are man and other animals.
The life cycle can be either hetroxenous (requiring two hosts)

or monoxenous (one host). Both sexual and asexual
reproduction occur in man.
There are five main developmental forms in the life cycle, but
only trophozoites and cyst stages are found in human. All
stages occur in the felines (cats).
164
Toxoplasma has two forms

1. Tachyzoites- occur in the early acute stage of infection.
2. Bradyzoites-occur in the chronic stage of infection,
develop slowly and multiply in the tissue to form a true
cyst.
Mood of Transmission
1. Ingestion of cysts in raw or under-cooked meat
2. Ingestion of oocysts in food, drink or from hands
contaminated with feces of an infected cat.
3. Transplacental/congenital
4. Blood transfusion
5. Organ transplantation
Incubation period- from 10-23 days. One common source

outbreak from ingestion of under-cooked meat is possible.
Period of communicability- Not directly transmitted from

person to person, except in utero. Oocysts shed by cats
sporulate and become infective 1-5 days later and may
remain infective in water or moist soil for about a year.
Cysts in the flesh of an infected animal remain infective as

long as the meat is edible and uncooked.
165
Susceptibility and resistance- Susceptibility to infection is

general, but immunity is readily acquired and most infections
are asymptomatic. Duration and degree of immunity are
unknown, but are assumed to be long-lasting or permanent.
Antibodies persist for a year, and probably for life. Patient
undergoing cytotoxic or immuno-suppressive therapy or
patients with AIDS are at risk of developing the disease.
General symptoms: Although severe symptoms may be

noted, Toxoplasmosis gondii symptoms are mild and mimic
those seen in cases of infectious mononucleosis. The acute
form of this disease is characterized by fatigue, lymphodenitis,
chills, fever, headache and myalgia. In addition to chronic
disease, the patient may develop maculopapular rash,
encephalomyelitis and hepatitis; retinochoriditis with
subsequent blindness has been known to occur on rare
occasions.
Congenital Toxoplasmosis: The typical symptoms in an

infected child include hydrocephaly, microcephaly,
choreoretinitis, convulsion and psychomotor disturbance.
Most of these infections ultimately result in mental retardation,
severe visual impairment or blindness.
166
Diagnosis
Clinical sign and symptom
Serological test
Demonstration of the agent in body fluid or tissue biopsy
cell culture
Treatment
1. Treatment is not routinely indicated for a healthy immuno-
competent host, except in an initial infection during
pregnancy or the presence of active choreoretinitis and
myocarditis or other organ involvement.
2. The preferred treatment for those with severe
symptomatic disease is: Pyrimethamine combined with
sufadiazine and folinic acid for four weeks.
3. For pregnant women, Spirmycin is commonly used to
prevent placental infection. If ultrasound or other studies
indicate that fetal infection has occurred, Pyrimethamine
and sulfadiazine should be considered.
Treatment for infants

1. Pyrimethamine
2. Sufadiazine
3. Folinic acid
167
1) The cause of primary infection with Toxoplasma can be

reduced by avoiding eating under-cooked or raw meat
and avoiding cyst-contaminated materials (i.e. cat’s litter
box).
2) Meat should be heated to 600c or frozen to kill cysts.
3) Hands should be washed thoroughly after work in the
garden and all fruits and vegetables should be washed.
4) Discourage cats from hunting.
5) Dispose cats’ feces daily.
6) Control stray cats and prevent them from gaining access
to sand boxes and sand piles.
7) Educate pregnant women.
To avoid cleaning litter pans or contact with cats.
Dietary meat; to heat to 60oc or freeze it.
To wear gloves during gardening.
8) Blood intended for transfusion into Toxoplasma sero-
negative immuno-compromised individuals should be
screened for antibody to toxoplasma gondii.
9) Patients with HIV/AIDS who have severe symptomatic
toxoplasmosis should receive prophylactic treatment
(Prymethamine, sulfadizine, folinic acid) throughout their
life span.
168
7.4 Animal Bite Diseases
7.4.1 Rabies
Definition
It is almost invariably fatal: acute vial encephalomyelitis
(attacking brain and meninges).
Infectious agent
Rabies virus
Epidemiology
Occurrence- Worldwide in wildlife particularly in developing
countries. It is primarily a disease of animals (zoonotic). It is
primarily an infection of carnivores transmitted through bite.
Reservoir- Dog is common in urban areas; in the wild, wild

carnivores and bats are reservoirs.
Mode of transmission- Transmitted with saliva of rabid

animal introduced by a bite or scratch. Transmission from
man to man is dead-ended.
Incubation period- Usually 3-8 weeks
Period of communicability -Usually 3-7 days before the

onset of the disease and throughout the course of the
disease.
169
Susceptibility and resistance- All mammals are susceptible

to varying degrees. Humans are more resistant to infection
than several animal species.
The clinical manifestation, which is the same in all species
including humans, has 3 phases:
Prodromal phase
Excitatory phase
Paralytic phase
Prodromal phase: Onset is heralded by a sense of

apprehension, headache, fever and nausea, abnormal
sensations at the site of inoculation (bite) is most significant,
(i.e. paraesthesia, tingling sensations at the bite site).
Excitatory phase or Aerophobia: Slightest sound/wind

excites the victim, irritability, restless, nervousness, tendency
to bite, are some of the symptoms.
Paralytic phase: Spasm of swallowing muscles leads to

drooling of saliva and fear of water (hydrophobia). Delirium
and convulsions form and death is often due to respiratory
muscle paralysis.
170
Diagnosis
History of bite by known rabid animal and the bitten
person show typical symptoms leading to clinical
diagnosis.
Treatment
1. Wound Care
Wash the wound with soap and water thoroughly to
decrease the viral load.
If there is bleeding cover the wound.
Never suture the wound as this will spread the virus.
2. Start anti-rabies vaccine immediately if it is proved to be
rabid animal bite.

1) Immunize all dogs and cats.
2) Detain and clinically observe for 10 days any healthy
appearing dog or cat known to have bitten a person.
3) Post exposure prophylaxis
Treatment of bite wounds
Specific immunologic protection
4) Keep dogs and cats at home.
5) Destroy stray animals where rabies is endemic.
171
7.5 Direct Contact Diseases
7.5.1 Anthrax
Definition
An acute bacterial disease usually affecting the skin, but
which may very rarely involve the oropharynx, lower
respiratory tract, mediastinum or intestinal tract.
Infectious agent
Bacillus anthracis, spore forming bacteria.
Epidemiology:
Occurrence- Worldwide. Primarily a disease of herbivores.
Humans and carnivores are incidental hosts. Primarily an
occupational hazard of workers who process hides, hair
(especially from goats), bone and bone products and wool:
and of veterinarians and agriculture and wildlife workers who
handle infected animals. Human anthrax is common
(endemic) in those agricultural regions of the world where
anthrax in animals is common, including countries in South
and Central America, southern and eastern Europe, Asia and
Africa.
Reservoir- Animals, normally herbivores, both livestock and

wildlife, shed the bacilli in terminal hemorrhages or spilt blood
172
at death. On exposure to air, the vegetative forms sporulate,

and the spores of B. anthracis, which are very resistant to
adverse environmental conditions and disinfections, may
remain viable in contaminated soil for many years after the
source animal infection has terminated. Dried or processed
skins and hides of infected animals may harbor the spores for
years and are the fomites by which the disease is spread
worldwide.
Mode of transmission-
Cutaneous anthrax: Contact with tissues of animals
(Cattle, sheep, goats, horses, pigs and others) dying of
the disease. Bite of flies that had partially fed on such
animals, contaminated hair, wool, hides, or products
made from them such as drums or brushes or contact
with soil associated with infected animals.
Inhalation anthrax: inhalation of spores in risky industrial
processes such as tanning of hides, or wool or bone
processing, where aerosols of B. antracis spores may be
produced.
Intestinal and oropharyngeal anthrax: ingestion of
contaminated meat; but there is no evidence that milk
from infected animals transmits anthrax.
N:B. The disease is transmitted among grazing animals

through:
173
contaminated soil and feed, and among omnivorous bone

meal or other feeds and among wildlife from feeding on
anthrax carcasses.
Vultures have been reported to spread the organism from
one area to another.
Incubation period- A few hours to seven days; most cases

occur within 48 hours of exposure.
Period of communicability- transmission from person to

person is very rare. Articles and soil contaminated with spores
may remain infective for decades.
Susceptibility and resistance- uncertain
Cutaneous Anthrax
Approximately 95% of human cases of anthrax are
cutaneous form and about 5% are the inhalation form.
Found on exposed areas of skin (head, neck, face and
hands).
Small red macules appear.
Lesion- progress to papule, vesicle or pustule during the
next week and formation of an ulcer with blackened
necrotic eschar surrounded by a highly characteristic,
expanding zone of brawny edema.
174
The early lesion may be pruritic but painless.

Small satellite vesicle may surround the original lesion
and painful non-specific regional lymphadenitis is
common.
Most patients are afebrile with mild or no constitutional
symptoms; in severe cases, however, edema may be
extensive and associated with shock.
Spontaneous healing occurs in 80-90% of untreated
cases but edema may persist for weeks.
In 10-20% of cases, infection progresses, bacteria
develops and is often associated with high fever and rapid
death.
Inhalation anthrax
Presentation of symptoms of severe viral respiratory
diseases makes early diagnosis difficult.
Acute phase supervenes after 1-3 days. With increasing
fever, dyspnea, stridor, hypoxia, and hypotension usually
leading to death within 24 hours.
Gastrointestinal Anthrax- Symptoms are variable and

include:
Fever, nausea and vomiting, abdominal pain, blood,
diarrhea, and sometimes rapidly developing ascites.
Diarrhea is occasional and massive in volume.
175
Oropharyngeal anthrax
Fever, sore throat, dysphagia, painful regional
lymphadenopathy toxemia, respiratory distress may be
evident.
The primary lesion is most often on the tonsils.
Diagnosis
Clinical data
Gram stain of wound discharge
Culture from the wound discharge or blood
Treatment
For Cutaneous anthrax
1. Penicillin-G IV until edema subsides and with subsequent
oral penicillin to complete the course (adults). For
Penicillin-sensitive adults, Ciprofloxacin, erythromycin,
Tetracycline, Chloramphenicol can be substituted.
2. Clean and cover the cutaneous lesions.
For Inhalation anthrax, Gastrointestinal and Anthrax

meningitis
High dose of penicillin is recommended.

1. Decontaminate wool and goat’s hair and improvement of
working condition for handlers of animal products.
176
2. Vaccination of susceptible groups and domestic

herbivores.
3. Carcasses of animals should be buried intact.
4. Butchering of infected animals should be avoided.
5. Education in mode of transmission and in care of skin
abrasions for employees handling potentially
contaminated articles.
6. Dust control and proper ventilation in hazardous
industries.
7. Treat all animals exposed to anthrax with Tetracycline or
penicillin.
7.6 Animal Reservoir Diseases
7.6.1 Leishmaniasis
Definition
A polymorphic protozoan disease of the skin and mucous
membrane or a chronic systemic disease caused by a number
of species of the genus leishmania.
Infectious agents
For cutaneous and mucosal Leishmaniasis
Leishmania tropica Leishmania donovani *
Leishmania major and Leishmania infantum *
Leishmania aethiopica*
177
For visceral Leishmaniasis

Leishmania donovani. *
Leishmania infantum. *
Leishmania tropica. * and
Leishmania chagasi. *
*Common agents in Ethiopia.
Epidemiology
Occurrence- It occurs in Pakistan, India and recently China,
the Middle East including Iran and Afghanistan, southern
regions of the former Soviet Union, sub-Saharan Africa,
Sudan, the highlands of Ethiopia, Kenya and Namibia. Urban
populations including children may be at risk. In the developed
world, the disease is restricted to occupational groups, such
as those involved in work in forest areas; to those whose
homes are in or next to a forest and to visitors to such areas
from non-endemic countries. It is common where dog
populations are high, generally more common in rural than
urban areas.
Reservoirs- locally variable; include human beings, wild

carnivores and domestic dogs.
Mode of transmission- Transmission is through the bite of

the female phlebotomine (sand flies). From person to person,
by blood transfusion, and sexual contact has been reported,
but rare.
Incubation period- at least a week; up to many months.
178
Period of communicability- Infectious to sand flies as long

as parasites remain in lesion, in untreated cases, usually a
few months to 2 years. Eventual spontaneous healing occurs
in most cases.
Susceptibility and resistance- Susceptibility is probably

general. Life-long immunity may be present after lesion due to
L. tropica or L. major but may not protect against other
leishmanial species.
Life cycle
TRANSMISSION
1. Promastigotes injected
through skin when sand fly
takes a blood meal
SANDFLY
3. Amastigotes ingested by sand fly.
4. Amastigotes become promastigotes.
5. Promastigotes multiply. Migrate to
head and mouth parts of fly.
HUMAN HOST*
2. Promastigotes taken up by
macrophages. Become amastigotes
Multiply in reticuloendothelial cells (VL)
or skin macrophages (CL, MCL).
* Leishmania species infect a wide
range of animals.
Fig. 7.2 Transmission and life cycle of Leishmania parasites VL: Visceral
leishmaniasis, CL: Cutaneous leishmaniasis MCL: Mucocutaneous
leishmaniasis. (From Monica Chesbrough, 1998, District Laboratory Practice
in Tropical Countries, Part One, Cambridge University Press, London.)
179
There are papules that further develop to ulcers. The
disease is characterized by fever, hepathosplenomegally,
lymphadenopathy, anemia, leucopoenia, thrombocy-
topenea, and progressive emaciation and weakness.
Diagnosis
Demonstration of the parasite (blood or tissue)
By culture of the motile promastigote
Using serologic test
Treatment
Pentalvalent antimonial agents
Pentamidine or
Amphotercin or
Aminoglycoside aminosidine or
Cytokine immunotherapy

1. The avoidance of outdoor activities.
2. The use of mechanical barriers such as screens and bed
nets.
3. Wearing of protective clothing.
4. Application of insect repellent.
5. Treatment of cases.
6. Vector control and elimination of reservoir host (e.g.
domestic dogs).
180
7.6.2 African Trypanosomiasis
Definition
A systemic disease caused by protozoa characterized by
fever followed by general weakness and cerebral involvement
leading to death.
Infectious agent
The commonest agents are:
T. Brucei rhodesiense
T. Brucei gambiense
Other species which are less important are;
T. Cruzi, which causes American Trypanosoniasis
Vectors for all species are tsetse flies of Genus Glossina.
Epidemiology
Occurrence-The trypanosomes that cause sleeping sickness
are found only in Africa. 20,000 new cases are reported each
year. This number surely under-estimates the true incidence.
T. brucei gambiense occurs and is widely distributed in the
tropical rainforests of Central and West Africa. Gambiense
trypanosomes are primarily a problem in rural population;
tourists rarely become infected. The principal reservoir of T.B
rhodesiense in savanna and woodland areas of Central and
East Africa are Trypotolerant antelope species. Humans
acquire T.B. rhodesiense infection only incidentally while
181
working in areas where infected vectors are present. T.

ganebie has no animal reservoir. However, T. rhodesiense
causes the more severe trypanosomiasis without sleeping
sickness. In Ethiopia, the distribution of Trypanosomiasis is
mostly found in Jinca, Afar, Setitu Humera, Konso, Moyale,
Woito, and Dilla.
Reservoir- for T. brucie gambiense it is only humans. For T.

brucie rhodesiense the reservoir is dog, cattle, fox, wolf and
human beings.
Mode of transmission- by the bite of infective Glossina

Tsetse fly during blood meal. Congenital transmission can
occur in humans. Direct mechanical transmission is possible
by blood on the proboscis of Glossina and other man-biting
insects, such as houseflies or in laboratory accidents
Incubation period- T. brucei rhodensiense: 3 days to few

weeks. T. brucei gambiense: several months up to one year.
Period of communicability- The disease is transmitted as

long as the parasite is present in the blood of infected person
or animal and infected Tsetse fly.
Susceptibility and resistance- All persons are equally

susceptible for the disease.
182
Life cycle
TRANSMISSION
1. Trypomastigotes injected
through skin when tsetse fly
takes a blood meal
TSETSEFLY
3. Trypomastigotes ingested by tsetse
fly
4. parasites multiply in mid gut.
Migrate to salivary glands.
5. Become epimastigotes and multiply.
Develop into infective metacyclic
HUMAN HOST* trypomastigotes.
2. Trypomastigotes multiply
in blood. Lymph and in
later stages. In CNS.
* T.b. rhodesiense infects a
wide range of game
animals and domestic
animals.
Fig. 7.3 Transmission and life cycle of T.b. rhodesiense and T.b gambiense.
(From Monica Chesbrough, 1998, District Laboratory Practice in Tropical
Countries, Part One, Cambridge University Press, London.)
Stage I (Signs & symptoms)

1. Painful trypanosoma chancre
2. Hematogenous and lymphatic dissemination
3. High body temperature
4. Lymphadenopathy discrete
5. Winter bottom’s sign (classic), painless enlargement of
lymph node
183
6. Malaise
7. Headache
8. Weight loss
9. Edema
10. Hepatomegally and
11. Tachycardia
Stage II
1. Abnormality in CSF
2. Day time somnolence
3. Tremors
4. Parkinson’s disease may appear
5. Hypertonia
6. Congestive heart failure
7. CNS disease develops
8. Coma and death
Diagnosis
Wet blood smear
Thick blood smear
Serological test
CSF analysis
Blood film
Bone marrow biopsy
184
Treatment
1. Pentamidine or
2. Etlornithine or
3. Helarsupron or
4. Trypansamide
These are drugs to be used for treatment of different stages.
For stage I (Normal CSF) – T.b. gambie treated with

Suramin or
Eflornithine or
Pentamidine
For stage II
Trypansamide
1. Public education on personal measures to protect against

insect bite.
2. Eradication of vectors.
3. Drug treatment of infected humans.
4. Avoiding areas to be known by harboring infected insects.
5. By wearing protective cloth and by using insect repellents.
6. Reducing tsetse fly number by
Identifying and studying the breeding habits of local vector
185
Selectively clearing the bush and wooden areas

especially around game reservoirs, water holes, bridges
and along rivers bank
Using and maintaining insecticide impregnated tsetse fly
traps.
7. Spraying vehicles with insecticide as they enter and leave
tsetse fly infested areas
8. Prohibit blood donation from those who have visited or
lived in endemic areas.
186
Review Questions
1. List the common zoonotic diseases and their main mode

of transmission.
2. Which of the Taenia species are most common in
Ethiopia?
a. Taenia solium
b. Taenia saginata
c. Trypanosomiasis
d. Echinococcus granulosis
3. What are the preventive and control methods for zoonotic
diseases?
187
CHAPTER EIGHT
FOOD-BORNE DISEASES (FOOD

POISONING, FOOD-BORNE
INTOXICATIONS, FOOD-BORNE
INFECTION)

List the common food-borne diseases.
Identify the difference between food poisoning and food
infection.
Describe the clinical manifestations and possible sources
of infection.
Participate in the diagnosis and management of food-
borne diseases.
Implement the preventive and control methods.
8.2 Introduction
Food-borne diseases, including food-borne intoxications and

food-borne infections, are terms applied to illnesses acquired
188
by consumption of contaminated food. They are frequently

and inaccurately referred to as food poisoning. While these
terms would include illnesses caused by chemical
contaminants (heavy metals and organic compounds), this
chapter will cover illnesses caused by toxins elaborated by
bacterial growth in the food before consumption
(staphylococcus aureus and botulism) and a food-borne
infection (salmonellosis).
8.3 Staphylococcal Food Poisoning

(intoxication)
Definition
An intoxication (not infection) of abrupt and sometimes violent
onset.
Infectious agent (Toxic agent)

Several enterotoxins of staphylococcus aureus, stable at
boiling temperature. Staphylococci multiply in food and
produce the toxins.
Epidemiology
Occurrence- Widespread and relatively frequent
Reservoir- Humans in most instances; occasionally cows with

infected udders.
189
Mode of transmission- By ingestion of a food product

containing staphylococcal enterotoxin. Foods involved are
particularly those that come in contact with food handlers’
hands, either without subsequent cooking or with inadequate
heating or refrigeration, (e.g. salad, sandwiches, sliced meat
and meat products, pastries, etc.). When these foods remain
at room temperature for several hours before being eaten,
toxin-producing staphylococci multiply and elaborate the heat-
stable toxin. The organisms may be of human origin, from
purulent discharges of an infected finger or eye, abscesses,
nasopharynyeal secretions.
Incubation period- 30 minutes to 8 hours, usually 2-4 hours.
Period of communicability- not applicable
Susceptibility and resistance- Most people are susceptible.
Sudden onset of vomiting and watery diarrhea
Fever and abdominal cramp
The intensity of illness may require hospitalization.
Diagnosis
Group of cases with characteristic acute predominantly
upper gastrointestinal symptoms and the short interval
190
between eating a common food item and the onset of

symptoms.
Culture –staphylococcal recovery (≥105organisms per
gram of food) or detection of enterotoxin from an
epidemiologically implicated food item confirms the
diagnosis.
Treatment
1. Fluid and electrolyte replacement if fluid loss is significant
particularly in severe cases.

1. Educate food handlers in strict food hygiene, sanitation
and cleanliness of kitchens, proper temperature control,
handwashing, cleaning of finger nails, need to cover
wounds on the skin, etc.
2. Reduce food-handling time (initial preparation to service)
to an absolute minimum, with no more than 4 hours at
ambient temperature. Keep perishable food hot (>60c0) or
cold (below 10c0).
3. Temporarily exclude people with boils, abscesses and
other purulent lesions of hands, face or nose from food
handling.
191
8.4 Botulism
Definition
A paralytic disease that begins with cranial nerve involvement
and progresses caudally to involve the extremities.
Infectious agent (Toxic agent)

Toxin produced by Clostridium botulinum (Neurotoxin)
Epidemiology
Occurrence- Worldwide occurrence. Home-canned foods,
particularly vegetables, fruits and less commonly with meat
and fish. Outbreaks have occurred from contamination
through cans damaged after processing. Commercial
products occasionally cause outbreaks but some of these
outbreaks have resulted from improper handling after
purchase. Food-borne botulism can occur when a food to be
preserved is contaminated with spores.
Reservoir- The bacteria is found in the soil and in the

intestine of animals.
Mode of transmission- Food ingestion in which preformed

toxin is found.
192
Incubation period- Neurological symptoms of food-borne

botulism usually appear within 12-36 hours, sometimes
several days, after eating contaminated food.
Period of communicability- not communicable
Clinical Manifestations
Illness varies from a mild condition to very severe disease
that can result in death within 24 hours.
Symmetric descending paralysis is characteristic and can
lead to respiratory failure and death.
Cranial nerve involvement marks the onset of symptoms;
usually produces diplopia, dysphagia. Weakness
progresses, often rapidly, from the head to involve the
neck, arms, thorax and legs; the weakness is occasionally
asymmetric.
Nausea, vomiting, abdominal pain may proceed or follow
the onset of paralysis.
Dizziness, blurred vision, dry mouth, and occasionally
sore throat are common.
No fever
Ptosis is frequent.
Papillary reflexes may be depressed: fixed or dilated
pupils are noted in half of patients.
193
The gag reflex may be suppressed; deep tendon reflexes

may be normal or decreased.
Paralytic illus, severe constipation and urinary retention
are common.
Diagnosis
Clinical- afebrile, mentally intact patients who have
symmetric descending paralysis without sensory findings.
Appropriate History.
Demonstration of organisms or its toxin in vomitus, gastric
fluid or stool is strongly suggestive of the diagnosis
Wound culture
Treatment
1. Hospitalize the patient and monitor closely.
3. Intubation and mechanical ventilation may be needed.
4. Antitoxin administration after hypersensitivity test to horse
serum.
5. Emesis and lavage if short time after ingestion of food to
decrease the toxin.

1. Ensure effective control of processing and preparation of
commercially canned and preserved foods.
2. Education about home canning and other food
preservation techniques regarding the proper time,
194
pressure and temperature required to destroy spores, the

need for adequate refrigeration, storage, boiling with
stirring home-canned vegetables for at least 10 minutes to
destroy botulinal toxin.
3. Canned foods in bulging containers should not be used,
eaten or tasted.
8.5 Salmonellosis
Definition
A bacterial disease commonly manifested by an acute
enterocolitis.
Infectious agent
Salmonella typhimurium and Salmonella enteritidis are the
two most commonly reported.
Epidemiology:
Occurrence- Worldwide
Reservoir- Domestic and wild animals including poultry,

swine, cattle, rodents and pets (tortoises, dogs, cats and
humans) and patients or convalescents are carriers,
especially of mild and unrecognized cases.
Mode of transmission:- ingestion of organisms in food

derived from infected food animals or contaminated by feces
195
of an infected animal or person. Raw and under-cooked eggs

and egg products, raw milk and its products, contaminated
water, meat and its products, poultry and its products.
Consumption of raw fruits and vegetables contaminated
during slicing.
Incubation period –from 6 –72 hours, usually about 12-36

hours
Period of communicability- extremely variable through the

course of infection; usually several days to several weeks.
Susceptibility and resistance- Susceptibility is general and

increased by achlorhydria, antacid therapy, gastrointestinal
surgery, prior or current broad spectrum antibiotic treatment,
neoplastic disease, immunosuppressive treatment and
malnutrition.
Self limited fever and diarrhea (bloody or dysenteric when
colon is involved)
Nausea, vomiting and abdominal cramp
Microscopic leukocytosis.
Diagnosis
Blood culture initially
Stool, culture
196
Treatment
1. Symptomatic
2. If there is an underlying immunosuppressive disease
(conditions like AIDS, lymphoma, immunosuppressive
treatment), treat the underlying cause.

1. Improved animal rearing and animal marketing
2. Quality testing of the known and commonly contaminated
foods
3. Avoid consuming raw or partially cooked eggs
4. Wear gowns and gloves when handling stool and urine
and handwashing after patient contact.
197
Review Questions
1. What is the basic difference between food poisoning and

food infection?
2. What is the common cause of food infection?
3. How do you prevent and control food poisoning?
198
CHAPTER NINE
NURSING RESPONSIBILITIES IN
THE MANAGEMENT OF
COMMUNICABLE DISEASES

List the different prevention and control methods for
common diseases in Ethiopia.
Implement the preventive and control measures for each
disease category at any level of health care.
The proper nursing management of communicable diseases

involves both trying to stop people getting diseases
(prevention) and looking after those who have them
(treatment and care). The two are frequently close related and
doing one without the other is only half the job. The measures
based on each disease category are described as follows:
199
For Oral-fecal transmitted diseases:

Control of diarrheal diseases including dysentery is only
possible when the problem of stool disposal is solved
(deep pit latrines in rural areas).
Providing handwashing facilities at toilets: wash hands
after going to toilet, wash hands before cooking or eating.
Fly control by proper refuse disposal and proper disposal
of feces.
- Screen toilets, cover latrines
- Screen kitchens and food stores
- Store left-over food where flies cannot reach it
- Spray with residual insecticides
Food should always be properly cooked.
Raw vegetables and fresh fruits without intact skins
should be avoided.
Milk should be boiled or pasteurized.
Protection, purification and chlorination of public water.
Health education based on dangers of bottle–feeding;
encourage cup/spoon feeding methods and encourage
prolonged breastfeeding.
Demonstrate prevention of dehydration by homemade
soup or salt solution.
Appropriate treatment of cases
200
For air-borne diseases

Ventilation removes used air and replaces it with clean
air.
Having too many people in the same room should be
avoided. This is especially important in prisons,
dormitories, boarding schools, and in urban housing
where many people may be forced to live in a single
room.
Health education about personal hygiene
- To cover the mouth when coughing and sneezing
- To use a hand kerchief or tissue paper for disposal of
nasal secretions and sputum
- Not to spit on the ground in or outside the house
For vector-borne diseases

Draining water or ditches, and any accumulation of water
around the village or filling in holes and ditches so that
water will not accumulate.
Clearing bush and grass along water banks and in the
village.
All containers likely to hold water are to be collected and
disposed.
No water container should have water in it longer than
one week.
Snails can be controlled by disturbing their habitant
through changes in water level, filling or damming
habitant, and clearing habitat.
201
Mosquito net should be used at night.

Appropriate treatment of cases and provision of
chemoprophylaxis.
For sexually transmitted diseases

Early diagnosis and treatment:- This is the most important
measure and not difficult to achieve.
Patients should be encouraged to bring their contacts
(including their husband or wives) for treatment. Failure to
do this will result in high numbers of infection.
Elimination of reservoirs: The reservoir is exclusively
human; it includes untreated patients and especially
unsuspected infectious persons in the promiscuous
women pool (PWP).
Regular examination and treatment of known prostitutes
and other promiscuous women will reduce the reservoir,
but will not completely eliminate the risk of infection
(contact must be treated).
Sex education
This is a form of health education and should be directed at

the groups at risk, especially: students, soldiers, laborers, etc.
Here it is important to stress :
- Dangers of sexual promiscuity
- The early signs and symptoms of STD
- The possibilities for individual prophylaxis.
- Normal sexual behavior
202
- The dangers of antibiotic chemoprophylaxis

Suggest periodical check ups for STDs for bar ladies and
other women at risk.
For Zoonotic diseases

Educate the public to:
- Prevent fecal contamination of soil, water, human and
animal foods
- Cook beef and pork
- Use latrines
- Avoid drinking untreated milk or eating products made
from untreated milk
- Eliminate infected animals
- Use barrier precaution (gloves and clothing in the
handling of carcasses and products of potentially
infected animals)
- Keep dogs and cats at home and immunize them
- Destroy stray animals where rabies is endemic
- Bury carcasses of animals intact
- Vector control and elimination of reservoir host
Education of workers to control dust by ventilating rooms
of hazardous industries where wool and goat’s hair is
processed
203
For food-borne diseases

Educate food handlers in strict food hygiene, sanitation
and cleanliness of kitchens, proper temperature control,
handwashing, cleaning of finger nails, need to cover
wounds on the skin, etc.
Temporary exclusion of people with boils, abscesses and
other purulent lesions of hands, face or nose for food
handling
Education about home canning and other food
preservation techniques.
Educate public to avoid eating canned foods in bulging or
damaged containers
Avoid consuming raw eggs or partially cooked ones
Wearing gowns and gloves when handling stool and urine
and handwashing after patient contact
204
Review Questions
1. State the major modes of disease transmission in

Ethiopia.
2. What are the main nursing responsibilities in managing
communicable diseases?
205
GLOSSARY
Albuminuria Urine containing protein

Anuria Cessation of the production of urine
Biopsy The removal and examination of tissue
from somebody who is ill, in order to find
out more about his/her disease.
Bloating Full of liquid or gas and therefore
abdomen is felt larger than normal in a
way that is unpleasant.
Case An infected or diseased person or animal
having specific clinical, laboratory and
epidemiological characteristics.
Cercariae The stage of the fluke life cycle that
develops from germ cells in a daughter
sporocyst. This is the final developmental
stage in the snail host, consisting of a
body and a tail that aids in swimming.
Chemoprophylaxis The administration of a chemical, including
antibiotics, to prevent the development of
an infection or the progression of an
infection to clinical disease.
Chemotherapy The treatment of diseases with the use of
chemical substances.
Chronic diarrhea Diarrhea which persists for more than two
weeks.
206
Contact A person or animal that has been in such

association with an infected person or
animal, or a contaminated environment as
to have an opportunity to acquire the
etiologic agent.
Cyst The immotile stage protected by a cyst
wall. In this stage the protozoan is readily
transmitted to a new host.
Epididymoorchitis Inflammation of testis and epididmis.
Fomites A subclass of vehicles including inanimate
objects such as articles of clothing which
can become contaminated and transmit
agents.
Health A state of physical, mental and social
wellbeing of an individual, not merely the
absence of disease or infirmity.
Health education he process by which individuals and
groups of people learn to behave in a
manner conducive to the promotion,
maintenance or restoration of health.
Hematemesis Vomitus consisting blood.
Host A person or other living animal including
birds that affords subsistence or lodgment
to an infectious agent under natural (as
opposed to experimental) conditions.
Hosts in which the parasite attains maturity
207
or passes its sexual stage are primary or

definitive hosts; those in which the parasite
is in a larval or asexual stage are
secondary or intermediate hosts.
Hydrocele Accumulation of serous fluid in the
scrotum
Immune individual A person or an animal that has specific
protective antibodies and/or cellular
immunity as a result of previous infection
or immunization, or is so conditioned by
such previous specific experience as to
respond in such a way that prevents the
development of infection and/or clinical
illness following re-exposure to the specific
infectious agent.
Immunity That resistance usually associated with the
presence of antibodies or cells having a
specific action on the microorganism
concerned with a particular infectious
disease or its toxin.
Unapparent The presence of infection in a host without
infection recognizable clinical signs or symptoms.
Unapparent infections are identifiable only
by laboratory means such as blood test or
by the development of positive reactivity to
specific skin tests. (Synonymous:
208
asymptomatic, subclinical, occult

infection).
Incidence The number of instances of illness
commencing or, of persons falling ill during
a given period in a specified population.
More generally the number of new events
(e.g. New cases of a disease in a defined
population within a specified period.)
Infected individual A person or animal that harbors an
infectious agent and who has either
manifest disease (patient or sick personal)
or unapparent infection (see carrier).
Intermediate host A host for only the larval or sexually
immature stages of parasite
development.
Jaundice A syndrome characterized by an increased
level of bile pigments in the blood and
tissue fluid.
Lymphadenopathy Enlargement of lymph glands in more than
one centimeter for a variety of disease
conditions.
Lymphadenitis Inflammation of the lymphatic vessels.
Melaena Feces containing blood.
Merozoite One of the trophozoite released from
human red blood cells or liver cells at
maturation of the asexual cycle of malaria.
209
Microfilaria A term used for the embryo of a filaria,

usually in the blood or tissues of humans
ingested by the arthropod intermediate
host.
Miracidium Ciliated first swimming larva of a
trematode, which emerges from the egg
and must penetrate the
appropriate species of snail in order to
continue its life cycle development.
Oocyst The encysted form of the ookinet, which
occurs on the stomach wall of anopheles
mosquito species infected with malaria.
Ookinete The motile zygote of plasmodium species
formed microgamate (male) fertilization of
a macrogamate (female).
Resistance The sum total of body mechanisms that
interpose barriers to the invasion or
multiplication of infectious agents, or to
damage by their toxic products.
Source of The person, animal, object or substance
infection from which an infectious agent passes to a
host.
210
References
1. Abraham S. Benenson, 1995, Control of Communicable

Diseases Manual, 16th edition, An Official Report of the
American Public Health Association, The United Book
Press, Inc, Baltimore.
2. Davidson, S., 1999, Principles and Practice of Medicine,
18th edition, Harcourt, Edinburgh, London.
3. Donowitz, 1996, Infection Control in the Child Care Center
and Preschool, 3rd edition, Williams Wilkins, USA.
4. Eshuis Manschot, 1978, Communicable Diseases: A
Manual for Rural Health Workers, African Medical and
Research Association, Nairobi.
5. Harrison, S., 1998, Principles of Internal Medicine, 14th
edition, McGraw-Hill, U.S.A
6. Hegazi M. 1994, Applied Human Parasitology, 1st edition,
The Scientific Book Centers, Cairo.
7. Kozier, et al, 1995, Fundamentals of Nursing, 5th edition,
Addison - Wesley, U.S.A
8. Madeleine Fletcher, 1992, Principles and Practice of
Epidemiology, Addis Ababa University, Ethiopia.
9. Meseret Shiferaw, Haile Tena, 1990, A Manual for
Students and Health Workers, Ministry of Health,
Ethiopia.
10. Ministry of Health, 1997, Manual of National
st
Tuberculosis and Leprosy Control Program, 1 edition,
211
Health Learning Materials Development and Production

Division, Addis Ababa, Ethiopia.
11. Ministry of Health, 2001, Health and Health-related
Indicators, Planning and Programming Department, Addis
Ababa, Ethiopia.
12. Ministry of Health, 2002, AIDS in Ethiopia, 4th edition,
Disease Prevention and Control Department, Addis
Ababa, Ethiopia.
13. Monica Cheesbrough, 1998, District Laboratory Practice
in Tropical Countries, Part One; Cambridge University
Press, London.
212

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LECTURE NOTES

For Nursing Students

Important Guidelines for Printing and Photocopying

©2004 by Mulugeta Alemayehu

This lecture note was written because there is currently no

In order to accomplish the above objectives, efforts have been

Specific learning objectives and review questions have been

I am highly indebted to acknowledge The Carter Center -

I would like to express my deep appreciation to Dr. Tadesse

My deep appreciation also goes to Ato Keneni Gutema, Ato

I would like to acknowledge Ato Abraham Alano and Ato

Last but not least my thanks also go to W/t Yiftusra Abebe

CHAPTER ONE: INTRODUCTION 1

CHAPTER TWO: DEFINITIONS, DESCRIPTIONS 8

2.1 Learning Objectives 8

CHAPTER THREE: ORAL-FECAL TRANSMITTED 23

CHAPTER FOUR: AIR-BORNE DISEASES 62

CHAPTER FIVE: ARTHROPOD OR 92

CHAPTER SIX: SEXUALLY TRANSMITTED 122

CHAPTER SEVEN: ZOONOTIC DISEASES 151

7.5 Direct Contact Diseases 172

CHAPTER EIGHT: FOOD-BORNE DISEASES 188

CHAPTER NINE: NURSING RESPONSIBILITIES IN 199

Fig. 3.1 The five “Fs” which play an important role in 24

Abbreviations and Acronyms

AFB Acid Fast Bacilli

STD Sexually Transmitted Disease

Diseases can be classified according to two major

Based on the cause, diseases can be broadly categorized as

However, most of the common diseases in Africa are

organisms. These are called communicable diseases,

1.2 Epidemiology and Scope of Communicable

In less developed countries, however, especially in the

Others, like yellow fever, acute febrile illnesses, trachoma

1.3 Epidemiological Terms and Definitions

Epidemiology- the study of the frequency, distribution and

promotion of health and to the prevention and control of health

The causes of diseases are classified epidemiologically

smoking leads to lung cancer. Having multiple sexual

Definition of other epidemiological terms:

1. How do you compare the impact of communicable

DEFINITION, DESCRIPTION OF THE

2.1 Learning Objectives

At the end of this chapter the student will be able to:

2.2 Communicable Diseases

These are illnesses due to specific infectious agents or its

indirectly, through an intermediate plant or animal host, vector

2.3 Chain of Disease Transmission

This refers to a logical sequence of factors or links of a chain

a. Infectious agent: An organism that is capable of

b. Reservoir of infection: Any person, animal, arthropod,

2. Animals: Some infective agents that affect man have their

3. Non-living things as reservoir: Many of the agents are

c. Portal of exit (mode of escape from the reservoir): This

d. Mode of transmission (mechanism of transmission of

1. Direct transmission: Consists of essentially immediate

b. Vector-borne transmission: Occurs when the infectious

1. Mechanical transmission: The arthropod transports the

2. Biological transmission: This is when the agent multiplies

Health promotion: by providing optimal nutrition for a

Prevention of exposure: by reducing exposure of the

Prevention of disease after exposure: by the provision

Detection and adequate treatment of cases: arrests the