Introduction To Parasitology: Pamanatasan NG Lungsod NG Maynila Modified By: Maria Cielo B. Malijan, MD, DPPS, FPSDBP
Introduction To Parasitology: Pamanatasan NG Lungsod NG Maynila Modified By: Maria Cielo B. Malijan, MD, DPPS, FPSDBP
Introduction To Parasitology: Pamanatasan NG Lungsod NG Maynila Modified By: Maria Cielo B. Malijan, MD, DPPS, FPSDBP
PARASITOLOGY
Pamanatasan ng Lungsod ng Maynila
Modified by: Maria Cielo B. Malijan, MD, DPPS, FPSDBP
Biological Relationships
• Symbiosis:
– is the living together of unlike organisms
– may also involve protection or other advantages to
one or both partners
Organism 1 = (+)
Organism 2 = (0)
Biological Relationships
Biological Relationships
2 organisms mutually
benefit from each other
Organism 1 = (+)
Organism 2 = (+)
Biological Relationships
Biological Relationships
Organism 1 = (+)
Organism 2 = (-)
Biological Relationships
Biological Relationships
• Medical Parasitology
– Concerned primarily with the animal
parasites of humans and their medical
significance, as well as their
importance in human communities
PARASITOLOGY
• Parasite
• Host
• Vector
PARASITES
Parasites
According to Habitat
Presence of an presence of an
endoparasite in a ectoparasite
host is called an inside the host is
INFECTION called an
INFESTATION
PARASITE
Parasites
need a host at
may exist in a free-
some stage of
their life cycle to
living state or may
complete their become parasitic when
development and the need arises
to propagate their
species
e.g. tapeworms
depend entirely upon
their host for
existence
• Accidental or Incidental parasite: establishes itself
in a host where it does not ordinarily live
2. FOOD
may contain the infective stage of the
parasite
3. :ARTHROPODS
e.g. mosquitoes as vectors of malaria
and filaria parasites
4. OTHER ANIMALS
(wild or domesticated) may harbor the parasite
– E.g. cats are direct sources of Toxoplasma ifnection
5. OTHER SOURCES
– Another person, his beddings and clothing, the immediate
environment he has contaminated
– E.g. asymptomatic carriers of Entamoeba histolytica working as
food handlers
AUTOINFECTION
where the self is the source of infection as seen in the life
cycles of E. vermicularis, Hymenolepis nana and Strongyloides
stercoralis
Modes of Transmission
• Mouth
– the most likely portal of entry
– Most cestodes, trematodes and protozoans are food borne
• Skin penetration
– : e.g. hookworms & Strongyloides
• Arthropods:
– as vectors transmit parasites through bites
– Agents of malaria, filaria, leishmaniasis and trypanosomiasis
• Congenital transmission:
– Toxoplasma gondii trophozoites can cross the placenta
– In transmammary infection with Ancylostoma and Strongyloides, the
parasites may be transmitted through the mother’s milk
Modes of Transmission
• Inhalation
– of air-borne eggs of Enterobius
• Sexual intercourse
– as in the case of Trichomonas vaginalis
Nomenclature
• Animal parasites are classified according to the International
Code of Zoological Nomenclature
• Intensity of infection:
– number of worms per infected person
– also referred to as worm burden
– measured directly by counting expelled worms during
treatment; indirectly by counting helminth eggs
excreted in feces expressed as eggs per gram (epg)
• Morbidity:
– clinical consequences of infections that affect an
individual’s well being
Diagnosis
• Demonstration of parasites
– E.g. eggs, adults, larvae, cysts, oocysts and trophozoites
• Cure rate:
– no. (expressed as percentage) of previously positive subjects
found to be egg-negative on examination of a stool or urine
sample at a set time after deworming
• Targeted treatment:
– group-level deworming where the (risk) group to be
treated (without prior diagnosis) may be defined by
age, sex, or social characteristics irrespective of
infection status
• Universal treatment:
– population-level deworming in which the community
is treated irrespective of age, sex, infection
status, or other social characteristics
Prevention and Control
• Morbidity control:
– the avoidance of illness caused by infections
• Information-education-communication (IEC):
– a health education strategy that aims to encourage
people to adapt and maintain healthy life practices
• Environmental management:
– manipulation of environmental factors or their
interaction with human beings
• Environmental sanitation:
• interventions to reduce environmental health
risks
– Includes safe disposal and hygienic management of human
and animal excreta, refuse and waste water
– Involves the control of vectors, intermediate hosts, and
reservoirs of disease
– provision of safe drinking water and food safety
Eradication versus Elimination
• Disease Eradication:
– permanent reduction to zero of the worldwide incidence of
infection caused by a specific agent, as a result of deliberate
efforts
– continued measures no longer needed
• Disease Elimination:
– reduction to zero of the incidence of a specified disease in a
defined geographic area as a result of deliberate efforts
– Continued intervention/surveillance still required
Damage Caused By The Parasite To Teh Host
• Immune processes
– Acquired immunity important in modifying severity
of disease in endemic areas
Immune Defense Against Parasitic Infections
• Mucus secretions
– envelop parasites (G. lamblia) affecting its motility
and reducing pathology on the host