CLINICAL PARASITOLOGY - PRELIMS

CLINICAL PARASITOLOGY
TERM

01
TDCI
BSMLS
2nd Year
2022-2023
MLS203B | LECTURE/LABORATORY | JENRY KEN VINCENT I. MIBATO, RMT, MSMT
OUTLINE
A. INTRODUCTION TO CLINICAL PARASITOLOGY
B. GENERAL ALBORATORY SAFETY
C. PARTS OF THE MICROSCOPE
D. MICROSCOPE – BASIC OPERATION AND MAINTENANCE
E. SARCODINA (AMOEBA)
F. SPECIMEN COLLECTION AND PROCESSING
G. LAB – MACROSCOPIC EXAMINATION

INTRODUCTION TO CLINICAL PARASITOLOGY

Parasitology - is the science that deals with organisms that take up • Insect bite
their abodes, temporarily or permanently, on or w/in other living • Entry via drilling through the skin
organisms for the purpose of procuring food, & w/ the relationship • Unprotected sexual relations
of these organisms to their host • Mouth-to-mouth contact
• Droplet contamination
History • Eye contact with infected swimming water
• The first written records of what are almost certainly PARASITISM
parasitic infections come from a period of • includes any reciprocal association in w/c a species
• Egyptian medicine from 3000-400 BC, particularly the • depends upon another for its existence
Ebers papyrus of 1500 BC discovered at Thebes • this association may be temporary or permanent
• A.lumbricoides eggs have been found in human • It involves 3 components
coprolites from Peru dating from 2277 BC. o The parasite
• Larval nematodes, possibly hook worms, have been o The host
found in fecal samples dated to about 200 BC from the o The Environment
Colorado Plateu
• In 1910, Marc Armand Ruffer found S.haeatobium eggs PARASITE-HOST RELATIONSHIP TERMS
in two Egyptian mummies dating from the, 1250-1000 BC. • Symbiosis - Living together; the association of two living
• A parasite, is an organism that lives on or inside another organisms that cannot exist independently, each of a
organism to the detriment of the host organism different species.
• The parasite grows, feeds, or uses shelter of the host • Commensal - Relating to commensalism; the association
organism (including the host itself) contributing between two different organisms in which one benefits
negatively to the relationship and has a neutral effect on the other
• Pathogenic - Parasite that has demonstrated the ability
• most parasitic infections are found in underdeveloped to cause disease
tropical and subtropical countries such as Haiti,
Guatemala, and Myanmar (Burma) and countries on the SYMBIOTIC RELATIONSHIP
African continent (Zeibig) • Mutualism - A symbiotic relationship in which both
• Increased population density, poor sanitation, marginal organisms benefit
water sources, poor public health practices, and • Parasitism - A symbiotic relationship in which one
environmental changes affecting vector breeding areas organism benefits and one is harmed
account for the prevalence of parasites. The habits and • Commensalism - A symbiotic relationship in which one
customs of the people living in these regions are also organism benefits and one is unaffected
contributing factors.
• The increased prevalence of global travel likely accounts THE PARASITE
for parasitic infections being spread to areas other than • is a living organism that obtains food & shelter from
where these infections originated. Individuals who travel another organism & derives all the benefit from the
to endemic areas are at risk of contracting parasitic association/relationship.
infections. Refugees, immigrants, and foreign visitors • comes a Greek words “para” (near) & “sites” (food)
may bring parasites with them when entering a non-
endemic area TYPE OF PARASITE EXAMPLE
Ectoparasite Parasite that is Flea
Population at Risk for Contracting Parasite
established in or
• Individuals in underdeveloped areas and countries on the exterior
• Refugees surface of a host
• Immigrants Endoparasite Parasite that is hookworm that
• Visitors from foreign countries established inside lives in the host's
• Individuals who are immunocompromised of a host gut
• Individuals living in close quarters (e.g., prisons) Facultative parasite when they are Strongyloides
• Children who attend day care centers capable of leading stercoralis
• Ingestion of contaminated food or drink both a free & a
parasitic existence
Modes of Parasite Transmission Obligate parasite when they take up Normal flora
(primarily water) a permanent
• Hand-to-mouth transfer residence in & are

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CLINICAL PARASITOLOGY - PRELIMS
completely Monoecious or having both the flukes
dependent upon hermaphroditic female & male
the host parasite reproductive
Incidental parasite One that Capillaria eggs organs in the same
establishes itself in individual
a host in which it
does not ordinarily SCIENTIFIC NOMENCLATURE
live; also known as • animal parasites are classified according to International
accidental parasite Code of Zoological Nomenclature
or spurious • each parasite belongs to a phylum, class, order, family,
parasite genus & species
Temporary parasite is free-living during Wuchereria • the names of genera & specie are printed in italics or if
part of its bancrofti not underlines; the generic name begins w/ a capital &
existence & seeks the specific name w/ a small letter:
its host o Ascaris lumbricoides
intermittently to
obtain PHASES OF PARASITISM
nourishment For a parasite to establish itself in its host, it must undergo various
especially during stages/phases:
feeding time; also
called intermittent I. Contact & entry to the host:
parasite this involves exposure (the act or process of introduction of the
Permanent parasite remains on or in parasite to its host) from one or more sources as:
the body of the • contaminated soil – soil polluted w/ human excreta
host from early life containing parasite stages
until maturity, • contaminated water – may contain viable cysts of
sometimes for its parasitic amoeba, intestinal flagellates or of infective
entire life cercaria of blood flukes
Pathogenic parasite causes injury to the • food containing the parasite’s immature
host by its • infective stage – as in some freshwater fishes, crabs, &
mechanical, crayfishes that serve as intermediate host of some
traumatic, or toxic Trematodes.
activities • blood-sucking insects – mosquitoes transmit malarial
Pseudoparasite is an bubbles parasites, leishmania, & others
artifact/object • domestic or wild animal harboring the parasite – dogs are
mistaken for a the direct sources for human infection w/ , Toxocara canis
parasite • hydatid cyst of Echinococcus granulosus; & others
Coprozoic or a parasite of Balantidium coli • another person – his clothing, bedding, or immediate
spurious parasite another animal environment which he has contaminated (ex. pinworn)
which pass through • one’s self – autoinfection comes about when one’s self is
the human body the source of reinfection; this accounts for some
w/o infecting the reinfections with Strongyloides stercoralis
host or w/o
causing any injury Modes of transmission through various portals of entry:
or damage • Direct (personal or intimate) or indirect contact w/
Aberrant parasite one which is never infected part – entry may be through skin or genitalia
transmitted from • Skin penetration from bites of arthropod vector or from
man to man but direct penetration of infective forms ( as in skin
which develops penetration of filariform larvae of hookworm)
abnormally in man. • Oral ingestion of contaminated food & drink containing
Periodic parasite is one in w/c its mosquito infective forms of the parasite – entry through mouth &
larval stage alimentary tract; includes hand-to-mouth transmission
develops in a host • Inhalation – inhalation of E. vermicularis eggs & at times
different from that of Ascaris from the air
of the adult • Transplacental (ex. congenital) infection w/ Toxoplasma
Transitory parasite is one which passes myiasis producing gondii & occasionally of malarial parasites.
its larval period of flies
development w/in II. Migration of Parasite in the Host to its Habitat
the body of the • ones the parasite has successfully entered the host’s
host, while the body, characteristically it is carried or actively migrates to
adult is free living a location where it matures & produces progeny.
Hematozoic those living in red malarial parasite
parasite blood cells III. Maturation and Reproduction
Dioecious parasite having female & roundworms • involves the parasites’ use of the host’s nutrients for
male reproductive growth, energy & multiplication; metabolic activities of
organs in different anabolism & catabolism occur in the parasites;
individuals or • Biological Incubation Period - period related to the
separate sexes development of the parasite. It starts w/ the entry of the
parasite to its host & ends as soon as the parasite or their

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CLINICAL PARASITOLOGY - PRELIMS
products can be demonstrated in the feces or their may serve as an additional source of infection
excreta, or in the circulating blood (parasitemia), by to man (ex. pig in B. coli).
aspiration, biopsy or other diagnostic procedures. • Susceptible host – one that is readily infected
• Clinical Incubation Period - refers to the interval between by a particular parasite.
exposure & the earliest evidence of symptoms produced • Refractory host – one that is not readily
as a result of the infection or infestation infected by a particular parasite
• Infection - is the entry & development or multiplication • Vector – is an animate or inanimate object that
of a pathogen in the body of the host (water, soil, milk, carries the infective stage of the parasite
food, etc. cannot be infected w/ pathogens, they can be • Carrier – is a person or animal that harbors a
contaminated only.). invasion of endoparasites. specific parasite w/o manifesting any clinical
• Infestation - is the lodgement, development, & symptoms & serves as a potential source of
reproduction of parasite esp arthropods on the surface of reservoir of infection for man or animals.
the body or in the clothing of man or the fur of animals.
Refers to the external parasitism of ectoparasites. PATHOGENESIS
• Parasitic infection - the infected host suffers very little the origin & development of disease; the dynamics of any disease
damage & no symptoms process.
• Parasitic disease - the infected individual develops
pathologic changes & symptoms of varying degree Damage produced by parasites on its host include the ff:
1. Traumatic damage - destruction of tissues following
IV. Exit & Development Outside of the Host for invasion of parasites as in the case of scabies mite or fly
Dissemination/Transmission/Spread maggots infesting the skin.
• gastrointestinal tract – via feces or vomitus (mouth) 2. Mechanical obstruction – a related damage brought
• kidney – via urine about by the presence of large worms like Ascaris or
• circulation – upon blood meal of arthropods/insects Taenia in the intestinal lumen thereby obstructing flow of
• nasal cavity – through sneezing / coughing intestinal contents.
• genitalia – sexual contact 3. Lytic necrosis – enzymes elaborated by many parasites
make it possible for them to digest available food in the
immediate environment as well as the tissue of the host
for penetration.
4. Stimulation of host tissue reaction – w/ few exception ,
all animal parasites provoke host tissue reaction. This
may consist of cellular proliferation & infiltration at the
site of the parasite, & it may involve systemic increase in
certain types of cells.
a. Hyperplasia – is an accelerated rate of cell
division resulting from an increased level of cell
metabolism; it commonly follows inflammation
& is the consequence of an excessive level of
tissue repair.
b. Hypertrophy – is an increase in cell size,
commonly associated with intracellular
parasites.
c. Metaplasia – describes the change of one type
THE HOST of tissue into another w/o the intervention of
• the living organism that harbors the parasite. embryonic tissue
• Classification of Hosts: d. Neoplasia – is the growth of cells in a tissue to
• Definitive host – harbors the adult or sexual form a new structure.
stage of the parasite e.
• Intermediate host – harbors the larval or 5. Toxic & allergic phynomena/inflammatory reaction to
asexual stage (ex. snail for the Schistosome) parasite or parasite products – several poisons or toxins
• Paratenic host - an organism that harbors the secreted by some parasites cause irritation & damage to
sexually immature parasite but is not necessary host.
for the parasite's development cycle to 6. Mechanical interference – this is the best exemplified by
progress. elephantiasis or edema of certain parts of the body esp
• also known as a carrier or transport host, one in the extremities as lymph fluid leaks out to tissues from
w/c the parasite remains viable but does not blockage of its flow by the presence of adult filarial
develop. worms.
• Incidental host – the infected individual is not 7. Secondary invaders – entry of an animal parasite may
necessary for the parasite’s survival or devt (ex. open pathways in the skin or the intestinal tract for
man in the case of trichinosis); the disease in invasion by other pathogenic organisms like bacteria.
this case is also referred to as zoonosis; a a. “Ground itch” in the skin at sites where
zoonotic infection is one that is normally hookworm larvae have penetrated is
transmitted only among animals. characteristically complicated by pyogenic
• Dead-end host – the host where the cycle for bacterial infection.
transmission of the parasite is such that it
cannot be transmitted further. IMMUNITY
• Reservoir host – a vertebrate host other than Immunity in animal parasitoses is rarely solid as it is in some of the
the definitive host w/c harbors the parasite & viral diseases like measles. A notable exception is found in
ensure continuity of the parasite’s life cycle & cutaneous leishmaniasis in w/c a natural infection followed by
spontaneous cure appears to confer immunity for life against

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CLINICAL PARASITOLOGY - PRELIMS
subsequent attack. Cases of human infections with foreign worms • Diarrhea
belonging to other animals are most frequent in children than in • Fever
adults. • Chills
• Abdominal pain
• Abdominal cramping
• Elephantiasis
THE ENVIRONMENT • Anemia
The presence or absence of a number of biological, chemical, & • Vitamin deficiency
physical factors in the environment directly or indirectly affects the • Bowel obstruction
densities & distribution of parasites. • Edema
• FLORA - vegetation that serves as food & shelter for • Enlargement of major organs
hosts, both definitive & intermediate, greatly influences • Skin lesions
parasite population. • Blindness
• FAUNA - animal population constitute potential hosts for
parasites so that the latter can maintain themselves in TREATMENT
the environment. • Antiparasitic medications
• WATER - some infective forms of parasites are free- • Change in diet
swimming & requires water to migrate & reach its host; • Vitamin supplements
this is exemplified by cercariae of Schistosomes. • Fluid replacement
• Host population density & behavior - population • Blood transfusion
densities of transport, intermediate & definitive hosts • Bed rest
affect parasite population densities.
• Influence of seasons, climate, temperature, humidity - PARASITE PREVENTION AND CONTROL STRATEGIES
both the incidence & most of human infection are • Development and implementation of parasite awareness
commensurate with the degree of personal & group education programs
sanitation, together w/ the resistance to pathogens to • Use of insecticides and other chemicals
w/c the individual is exposed. • Use of protective clothing
• Use of protective netting
DIAGNOSIS • Proper water treatment
• Signs & Symptoms? • Good personal hygiene
• Specimen for Diagnosis? • Proper sanitation practices
• Satisfactory for examination? • Proper handling, cooking, and protection of food
• No contaminants? • Avoidance of unprotected sexual relations
• Symptoms Associated with Parasitic Disease Process

GENERAL LABORATORY SAFETY

Why Practice Lab Safety at all times • Length should be up to knee when standing and should
• To enable staff to work safely with potentially infectious entirely cover the lap when sitting
organism • Disinfect before laundry
• To prevent unintentional exposure of lab staff to a
pathogen Laboratory shoes/Shoes
• To prevent its unintentional release to the environment • Shoes must cover the toes, upper part of the feet, and
have closure to the back of the heel.
Components of Lab Safety • A dedicated laboratory shoes should be available in the
• Facilities facility.
• Admin control
• Containment principles Wearing of masks
• Emergency preparedness • Surgical Mask should be worn at all times in the
• Safety equipment laboratory.
• Practices procedure • RESPIRATORS - Protect the wearer from inhaling droplet
nuclei
Gloves • MASKS - Prevent the spread of microorganisms from the
• Disposable, powder free wearer
• In light of the COVID-19 pandemic, the use of double Donning
gloves is recommended. • Laboratory Shoes
• Wearing gloves can give technicians a false sense of • Laboratory coat
safety O • Surgical Mask
• Regular and thorough hand washing is most essential • Bouffant cap
• Do not reuse gloves • inner gloves
• Do not wear gloves outside of the laboratory • Outer gloves
• Shoe cover
Laboratory Gown
• Appropriate size Doffing
• Leave coats at worksite • Outer gloves
• Buttoned • Shoe cover
• Fasten laboratory coat when worn • Laboratory coat
• Covers the whole arm with elastic cuff • Bouffant cap
• Use appropriate size and type O • inner gloves.
• Do not wear outside of the laboratory • Mask

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CLINICAL PARASITOLOGY - PRELIMS
• Solvents and oils must be segregated into the correct
GENERAL HAZARDS IN THE LABORATORY waste bottle or drum
• Fire • Your department will help you determine what to do with
• Breakage of glassware chemical or biological materials
• Sharps • All materials used should be considered contaminated!
• Spillages
• Pressure equipment & gas cylinders WHEN IN DOUBT- ASK
• Extremes of heat & cold • Do not carry out a new or unfamiliar procedure until you
• Chemical hazards have been fully trained & understand the precautions
• Biological hazards • necessary for safe working
• Radiation
Sodium hypochlorite
Flammable substances • Sodium hypochlorite (household bleach) should be used
• Use minimum quantity at a concentration of 10% in water
• Store in special storage cabinet • Diluted solutions should be prepared daily.
• Use temperature-controlled heating sources • Advantage
• (ex. water-bath rather than hot-plate or Bunsen burner) o Broad spectrum of antimicrobial activity
o Readily available
Fire Safety o Inexpensive
• Make sure that you know what to do: o Property to decontaminate and degrade
• If you have a fire contaminating DNA
• If you hear a fire alarm • Disadvantage
o Corrosive to metals
o Inactivated by organic matter
Spillages o Discolor or bleaches fabrics
• Clear up spillage promptly o Unstable
• Dispose of any hazardous material as toxic waste
Alcohol
• Messy workers are usually poor workers
• Ethanol (70%), isopropyl alcohol (709%).
General Tidiness • Advantage
• Keep your workplace tidy o They do not leave residues on treated items
o Can be used in SC and bench top
• Clear up waste, deal with washing up and put things away
as you finish with them • Disadvantage
o Volatile
• Make sure everything is safe before you leave things
o Flammable
unattended
• A tidy laboratory avoids accidents to everyone
Phenolic compounds
• Phenolic compound should be used at a concentration of
Laboratory Equipment
10% in water.
• Never use any laboratory equipment unless you are
• Advantage
trained & have been authorized to do so
o Used for decontaminating equipment and
• As well as injuring yourself you may cause very costly
single-use items prior to disposal.
damage
• Disadvantage
o Inhalation, dermal exposure is irritating to skin.
First Aid
o Ingestion of phenol is considered to be toxic
• All laboratory workers should undergo simple first aid
o Because of its toxicity and odor, phenol
training
derivatives are generally used in place of
• For ALL chemical splashes, wash with plenty of water for
phenol.
10 minutes
• Control bleeding with direct pressure, avoiding any
How to clean surfaces?
foreign bodies such as glass
• Wipe with 10% bleach solution or 5% Phenol
• Contact time for 10-15minutes
Waste Materials
• Wipe with 70% alcohol two times
• Part of your risk assessment will be to determine how to
dispose of waste lab materials safely

PARTS OF THE MICROSCOPE AND THEIR FUNCTION

• Body Tube – Reflects light up to the viewers eye

• Nose Piece – Allows for quick change of objectives
• Low Power Objective – The first lens you use when doing
proper microscope work. Usually 4 X
• Medium Power Objective – The second lens you use
when doing proper microscope work. Usually 10 X
• High Power Objective – The highest magnification used.
Usually 43 X. NEVER use the course adjustment when
using this lens.
• Stage Clips – Use to keep the slide in place.

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CLINICAL PARASITOLOGY - PRELIMS
• Diaphragm – Use to vary the amount of light passing
through the slide. Usually it is better if the amount of light
is low. • Place slide on a flat surface.
• Light Source – Sends light up through the diaphragm and • Place a drop of water on the slide. Add the specimen to
through the slide for viewing the drop of water (at times, you may want to have the
• Eye Piece—The part you look at with your eye. Usually 10 specimen already on the slide before adding the water).
X magnification. • Hold the coverslip by its sides and lay its bottom edge on
• Neck – Used to safely transport microscope the slide close to the specimen. Holding the coverslip at a
• Stage – Slides are placed on this 45° angle helps.
• Coarse Adjustment – Used to make large changes in • Slowly lower the coverslip so that it spreads the water
focus. NOTE Never use this when viewing on high power out. If you get air bubbles (looking like little black
• Fine Adjustment – Used to small adjustments of focus doughnuts), gently press on the coverslip to move them
• Base – Used to safely transport the microscope to the edge. If there are dry areas under the coverslip,
add a little more water at the edge of the coverslip. Too
HOW A LIGHT MICROSCOPE WORKS much water can be dabbed off with a piece of paper
• Use lenses to make small objects appear larger towel
• Compound light microscope: Two lenses separated by a
tube Why is this a preferred procedure?
• Lenses magnify an object by bending the light that passes • The cover-slip will prevent the slide from breaking.
through the lens • The organisms will be more evenly distributed.
• Magnification: ability to make things appear larger than • The possibility of breaking the cover-slip is reduced.
they are • The possibility of trapping air bubbles is reduced.
• Resolution: fineness of detail that can be seen in an image

HOW TO PREPARE A SLIDE

THE MICROSCOPE: BASIC OPERATION AND MAINTENANCE

• The Brightfield Microscope - A microscope is an mold strips, and temperature-controlled cabinets can be
instrument that is used to magnify small objects useful.
• HPO for DFS • Proper storage - Cover the microscope with vinyl cover
• OIO for blood parasites and store it in a place free from moisture and dust;
• Immersion oil must have medium viscosity and a maximum humidity <75%.
refractive index greater than 1.5. DO NOT use cedar wood • Cleaning the microscopic lens - Clean the microscope
oil because it leaves a sticky residue on the lens. lens gently with 95% alcohol and lens paper or soft tissue
paper by wiping it in a circular manner, starting from the
MICROSCOPE MAINTENANCE inner part going to the outer edge.
• Treat the microscope with care! NEVER expose it to sharp o NEVER wipe using zigzag movements.
knocks, vibrations, moisture, dust, or direct sunlight. o Direct pressure from the fingers should NEVER
• Humidity causes fungal growth on the surfaces of lenses be applied to the glass lens surface.
and prisms. This can cause cloudiness of the view field • The following materials are NOT used in cleaning the
and rusting of metal parts of the microscope. microscope:
• What can you do about this? Always keep the glass o Chloroform Acetone – toxic
surface as clean as possible and free of dirt and o Xylene Toluene Diethyl ether – leaves surface
fingerprints. In very humid areas, use of silica gel, anti- residue
o Carbon Tetrachloride – harmful to the
environment
SARCODINA (AMOREBA)
PARASITE NOMENCLATURE AND CLASSFICIATION

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PROTOZOA • Cilia – in ciliates; numerous short threads arising from
• are unicellular organisms that occur singly or in colony basal granules w/in the cytoplasm & are distributed over
formation the surface of the body.
• each protozoan is a complete unit capable of performing • Sporozoates – are the only motile form of protozoa
the physiologic functions that in higher organisms are o Have well developed sexual and asexual stages
carried on by specialized cells o Entire group is parasitic in nature and are
• most are free-living harmful
• Most of which are harmless free living and inhabits water o Some common examples of sporozoates and
and soil. A few species are pathogenic in nature parasitize their infections are:
human and other animals causing hundreds of million of ▪ Plasmodium (causative agent of
infections in a year around the world. Malaria, causes 100 to 100 million
infection world wide)
Morphology ▪ Toxoplasma Gondii (causes
• Protozoa are Eukaryotic resemble to animal cell, contain Toxoplasmosis)
major cell organelles (including Nucleus, Mitochondria)
• Their organelles are highly specialized for feeding, Reproduction in Protozoa
reproduction and movement Protozoa can reproduce their off spring by both Sexual and
• The cytoplasm of protozoa are divided into an outer layer Asexual methods
called Ectoplasm and an inner layer called Endoplasm 1. Asexual Methods
• Ectoplasm helps in movement, feeding and Protection • Simple Binary Fission - where the protozoan divides into
• Endoplasm houses Nucleus, mitochondria and food 2 equal parts; longitudinal division occurs in the
• Some protozoa have special appendages Flagella and cilia flagellates while in ciliates, it is transverse; is the
that helps in their movements simplest form of division
• Freshwater protozoa have contractile vacuoles to pump • Schizogony or Multiple Fission - where 2 or more
out excess water daughter cells or products of division result. The
• Their shape may remain constant (specially in Ciliates) or nucleus of the parent cell first undergoes repeated
change constantly (as seen in Amoeba) division & then the cytoplasm collects around them
• The size of Protozoa is range between 3 to 300 • Endodyogeny - in this form of division, the cell
micrometer. undergoes a single internal budding resulting in the
• Few ciliate and Amoeba are larger enough to be seen with formation of 2 daughter cells; seen in Toxoplasma &
naked eyes (they are about 4 to 5 mm). related organism
2. Sexual Methods
• Except Sporozoates, all types of protozoa are motile
either through Flagella, cilia or Pseudopodia • Syngamy / Gametogony - sexually differentiated cells
called gametes unite permanently & complete fusion of
• Have Eyespot that can detect change in light
the nuclear materials takes place. The resulting
• Respond to light & learn by trial & error
organism is called a zygote. This is found among
protozoans.
• Conjugation - observed among Ciliates where for
instance 2 Paramecia unite along their oral surfaces, the
macronuclei disintegrate & the micronuclei in each
organism divide twice. All daughter nuclei disintegrate
except one; there’s no increase in the number of cells

Life Cycle
Excystation
• where cyst stage becomes trophozoite
• 3 favorably factors that are possibly involve in
excystation:
o osmotic change in the medium
Classification of Protozoa o enzymatic action of the enclosed organism on
• Protozoa are classified on the basis of their motility and the inner surface of the cyst wall
method of reproduction o favorable pH & enzymatic action of the host
tissues
• They are classified into Four main types
Encystation
o Sarcodina (Amoeba)
o Flagellates • morphological formation of cyst from the trophozoite
o Ciliates • involves 5 factors:
o Sporozoates o deficiency or overabundance of food supply
o excess of catabolic products of the organism
Locomotory organelles arising from the ectoplasm may vary or of associated bacteria
from: o marked change in pH
• Pseudopodia (false feet) – in Amoeba where crawling o desiccation of the medium
movement is accomplished by the extension & retraction o depletion or excess O2 supply
of its ectoplasm called pseudopodia, hence the irregular
form. The major protozoan pathogens are grouped according to the
location in the body where they most frequently cause disease.
• Flagella – in flagellates; delicate, hair-like projections of
1. Within the intestinal tract, 3 organisms are the most
the cytoplasm arising from the kinetoplast within the
important:
cytoplasm.
a. the ameba - Entamoeba histolytica
b. the flagellate - Giardia lamblia

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CLINICAL PARASITOLOGY - PRELIMS
c. the sporozoan - Cryptosporidium species • Anal-oral transmission also occurs (ex. among male
2. In the urogenital tract, the flagellate Trichomonas homosexuals)
vaginalis is common • No animal reservoir
3. The blood & tissue protozoa are a varied group • The ingested cysts differentiate into Trophozoites in the
consisting of the flagellates Trypanosoma & Leishmania ileum but tend to colonize the cecum & colon
& the sporozoans Plasmodium & Toxoplasma. The • Trophozoites invade the colonic epithelium & secrete
important opportunistic lung pathogen Pneumocystis enzymes that cause localized necrosis; little
was recently classified as a fungus. inflammation occurs at the site; as the lesion reaches the
muscularis layer, a typical “teardrop” ulcer forms that
THE AMOEBAS can undermine & destroy large areas of the intestinal
epithelium; progression into the submucosa lead to
invasion of the portal circulation by the trophozoites
• By far the most frequent site of systemic disease is the
liver
• E. histolytica infection is found worldwide but most
frequent in tropical countries especially in areas w/ poor
sanitation
• The disease is widely prevalent among male homosexuals

Clinical Findings
• Acute intestinal amebiasis presents as dysentery (ex.
Entamoeba Histolytica bloody, mucus containing diarrhea) accompanied by
Common associated disease or condition names: lower abdominal discomfort, flatulence & tenesmus.
• Intestinal amebiasis • 90% of those infected are asymptomatic carriers (whose
• Amebic colitis feces contain cysts that can be transmitted to others)
• Amebic dysentery • Amebic abscess of the liver is characterized by right-
• Extraintestinal amebiasis. upper-quadrant pain, weight loss, fever & a tender,
enlarged liver; right-lobe abscesses can penetrate the
Important Properties diaphragm & cause lung disease
• The life cycle of E. Histolytica has 2 stages: • Most cases of amebic liver abscess occur in patients who
• CYST have not had overt intestinal amebiasis.
o The nonmotile form which predominates in
non-diarrheal stools Laboratory Findings
o are not highly resistant & are readily killed by Stool Examinations
boiling but not by chlorination of water • Trophozoites in diarrheal stools – should be examined
supplies; are removed by filtration of water w/in 30mins of collection to see the ameboid motility of
o has 4 nuclei, an important diagnostic criterion. the trophozoite
o Morphology o trophozoites characteristically contain ingested
▪ 8 to 22 µm, with an average range of RBC
12 to 18 µm. It is the Infective Stage o the most common error is to mistake fecal
▪ The presence of a hyaline cyst wall leukocytes for trophozoites
(thick chitinous wall) which makes it • Cysts in formed stools – at least 3 specimens should be
highly resistant to gastric acid, examined ‘coz cysts are passed intermittently.
adverse environmental conditions
and chlorine concentration. Laboratory Diagnosis
▪ It starts as uninucleate body but later 1. Wet Mount in saline
nucleus divides into two and later 2. Iodine-stained wet mount
four. 3. Fixed Trichrome-stained preparation
▪ Cysts are only present in the lumen of a. helpful in distinguishing amebic
colon and in the formed stool. (<polymorphonuclear leukocytes) from
• TROPHOZOITE bacillary dysentery (> polymorphonuclear
o The motile amoeba leukocytes)
o Found w/in the intestinal & extra-intestinal 4. Sigmoidoscopy procedure
lesions & in diarrheal stools 5. Culture - TYI-S-33 medium
o Upon excystation in the intestinal tract, an 6. Immunologically based procedures- antigen tests,
ameba w/ 4 nuclei (cyst) emerges & then enzyme-linked immunosorbent assay (ELISA), indirect
divides to form 8 trophozoites hemagglutination (IHA), gel diffusion precipitin (GDP),
o The mature trophozoite has a single nucleus w/ and indirect immunofluorescence (IIF).
an even lining of peripheral chromatin & a
prominent central nucleolus (karyosome) Treatment
o Antibodies are formed against trophozoite • Metronidazole (flagyl) plus iodoquinol - treatment of
Antigens in invasive amebiasis, but they are not choice for symptomatic intestinal amebiasis or hepatic
protective; prior infection does not prevent abscesses; hepatic abscesses need not be drained.
reinfection; but the Antibodies are useful for • Paromomycin, Diloxanide Furoate (Furamide), or
serologic diagnosis. Metronidazole (Flagyl) - for asymptomatic cyst carriers

Pathogenesis and Epidemiology Prevention and Control

• Cysts are transmitted primarily by the fecal-oral route in • avoid fecal contamination of food & water
contaminated food & water • observe good personal hygiene (ex. hand washing)

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CLINICAL PARASITOLOGY - PRELIMS
• purification of municipal water supplies is usually • Proper use of the ocular micrometer is therefore
effective but amebiasis outbreaks still occur when essential to obtain correct measurements of suspected
contamination is heavy organisms.
• use of “night soil” (human feces) for fertilization of crops • The prevalence of E. hartmanni appears to be similar to
should be prohibited that of E. histolytica in areas in which specific and
• in endemic areas, vegetables should be cooked accurate diagnoses have been made.
• Mode of Transmission and prevention and control same
Entamoeba Coli with E. histolytica
• Found worldwide. Warm climates also occur in cold • Typically Asymptomatic
climates, such as Alaska. Geographic areas that have poor
hygiene and sanitation practices are at the greatest risk Entamoeba Polecki
of becoming endemic with E. coli. As with the other • Trophozoites 8-25 µm, Cyst 10-20 µm
intestinal amebas, E. coli is transmitted through the • 1 nuclei both Troph and Cyst
ingestion of the infected cyst through contaminated food • E. polecki trophozoites exhibit progressive, unidirectional
or drink. motility in diarrheal stool
• Asymptomatic and non-pathogenic • The presence of fine and evenly distributed peripheral
• Proper disposal of human feces, proper personal hygiene chromatin is the most common form seen.
practices. Protection of food and drink from flies and • Diagnosed by examining stool samples
cockroaches is also necessary to break the E. coli • Primarily considered a parasite of pigs and monkeys and
transmission cycle. it is usually rare to humans
• Ingestion of the E. polecki cyst is most likely responsible
Difference Between E. Histolytica & E. Coli for the onset of infection. Human to human as well as pig
FEATURES E. histolytica E. coli to human are the major routes of parasite transmission
1. Cyst • Usually Asymptomatic. Diarrhea for patients with
size 8-22 u 8-35 u symptoms
nuclear membrane Thin Thick
Endolimax Nana
# of nuclei 1-4 1-8
• Non-pathogenic
chromatoidal bar Cigar-shaped Broomstick/splinter • Trophozoites 5 to 12 µm. Cyst is spherical, ovoid,
ed ends ellipsoid, size 4-12 µm.
2. Trophozoite • Exhibit sluggish, nonprogressive motility, which is
size 8-65 u 12-55 u accomplished by blunt, hyaline pseudopods.
pseudopods Long & finger like Short & • The karyosome is typically large and irregularly shaped,
round/blunt and is often described as blotlike in appearance.
motility Progressive & Sluggish & non- • The absence of peripheral chromatin is a key feature that
directional directional aids in the identification of E. nana trophozoites.
nucleus Central karyosome Eccentric / off • Food or drink contaminated with E. nana infective cysts
(bull’s eye center karyosome
karyosome) Iodamoeba Bütschlii
cytoplasm Clean w/ rbc Dirty w/ vacuoles • Non-pathogenic
bec they feed on • Trophozoites (8-22 µm), Cyst (5-22 µm)
bacteria & • Trophozoites characteristically exhibit progressive,
undigested food sluggish motility. The single nucleus consists of a large,
particle usually central karyosome surrounded by refractive
achromatic granules.
Entamoeba Hartmanni • Examination of stool samples for the trophozoites and
cysts
• Iodine wet preps in the identification of cysts
• Glycogen mass remains unstained following trichrome
staining.
• Infective cysts are ingested in contaminated food or
drink. Hand-to-mouth transmission may also occur.

Entamoeba Gingivalis
• Trophozoite size from 8 to 20 µm and exhibit active
motility.
• Food vacuoles containing phagocytosed and partially
digested white blood cells (leukocytes) and epithelial cells
of the host, bacteria, and ingested red blood cells.
• The only ameba that ingests white blood cells.
• NO known cyst stage
• Specimen for diagnosis- Mouth Scrapings
• Other specimens - tonsillar crypts, pulmonary abscess,
sputum, vaginal and cervical materia;.
• Infections are contracted via mouth-to-mouth (kissing)
and droplet contamination, which may be transmitted
through contaminated drinking utensils.
• No symptoms and nonpathogenic

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CLINICAL PARASITOLOGY - PRELIMS
• Frequently recovered in patients suffering from pyorrhea • N. fowleri is primarily found in warm bodies of water,
alveolaris. including lakes, streams, ponds, and swimming pools.
• Improved oral hygiene for prevention & control • Primary amebic meningoencephalitis (PAM) occurs when
the ameboid trophozoites of N. fowleri invade the brain,
FREE LIVING AMOEBA causing rapid tissue destruction.
They are ubiquitous in nature
Found commonly in soil and water, where they feed on bacteria. Acanthamoeba Spp.
They produce diseases in CNS and eyes.
free-living amoeba because they live in fresh water & moist soils;
infection often occurs during summer when people swim in fresh
water lakes & swimming pools.

Naegleria fowleri
Trophozoite
• Size: 8-22 µm
• Motility: Slug-like, blunt pseudopods
Flagella
• Size: 7 to 15 µm
• Motility: jerky movements or spinning
Cyst
• Size: 9 to 12 µm
• Motility: None progressive

The Cycle of N. Fowleri

• Spine-like pseudopods, known as acanthopodia,

• Acanthamoeba infections occur primarily in
immunocompromised individuals.
• Contact lens wearers, particularly those wearing soft
contacts, may be at risk of contracting Acanthamoeba
eye infections.
• Granulomatous amebic encephalitis. CNS infections with
Acanthamoeba are also known as granulomatous amebic
encephalitis (GAE).
• Acanthamoeba keratitis. Acanthamoeba infections of the
cornea of the eye are known as amebic keratitis.

Naegleria fowleri Acanthamoeba

1. acute meningoencephalitis 1. chronic
in normal hosts meningoencephalitis in
• Infections occur in healthy persons, usually children immunocompromised
• Trophozoites usually enter the body through mucous hosts
membranes while an individual is swimming 2. Ameboid trophozoites only 2. w/ cysts &trophozoites
• can penetrate the nasal mucosa & cribriform plate to in brain tissue (no cysts) found in brain tissue
produce a purulent meningitis & encephalitis that are
3. no corneal infection 3. corneal infection (diagnose
usually fatal
by corneal scrapings)

SPECIMEN COLLECTION AND PROCESSING

General Considerations for Proper specimen collection, Transport • If delayed, it should be preserved with fixed
and Preservation Procedures solutions
• A stool sample can be collected on a clean cardboard or - Time frame to demonstrate the motility of protozoan
a bedpan. It is important that samples collected are not trophozoites, a fresh specimen is required.
contaminated with urine. These must be promptly • Protozoan cysts are more likely to be found in formed
transferred to a clean, dry, sterile, wide-mouthed stools than trophozoites.
container with a tight-fitting lid with sufficient moisture • If amoebiasis or intestinal giardiasis is suspected, it is
before submitting to the laboratory. recommended that patients submit at least 3 stool
• The stool should be collected in sufficient amounts so samples, one every other day. Direct wet mount is done
that repetition of examination can be done if necessary. for watery or soft stools only, while fecal concentration
• 2-5 gram sample technique, and a permanently stained smear can be used
• Pea or thumb size for stool examination.
• Fresh stool sample must be delivered and processed into • Specimen must be collected before the start of treatment
the laboratory based on the following guidelines: (antibiotic, antielminths, antidiarrhea drugs, antacids,
• Liquid stool (within 30min) laxatives, hypertonic salt enemas).
• Semisolid (within 1 hr) • Feces containing barium, bismuth, kaolin and mineral oil
• Formed (within 1hr) should be rejected for possible result interference.
Resubmit 5-10 days.

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CLINICAL PARASITOLOGY - PRELIMS
• Stool should not be retrieved from toilet bowl water • Easy preparation • Contains mercuric
because free-living protozoa and nematodes may be of permanent chloride
confused with human parasites. smears stained • Difficult to
• Water may destroy select parasites, such as schistosome with such as prepare in the
eggs and amebic trophozoites. trichome laboratory
• Toilet paper in the stool specimen may mask parasites or (solution both • Not suitable for
make examination of the sample difficult. preserves concentration
• The specimen container should be labeled with the organisms and procedures
patient’s name and identification number, the makes them • Cannot be used
physician’s name, and the date and time of sample adhere to slides) with
collection. • Preserved immunoassay kits
• When handling all specimens, gloves and a protective samples remain • Not suitable for
coat should be worn at all times. stable for several acid-fast, safranin
months. and chromotrope
NEVER LABEL ON THE LID stains
• Label patient’s name and identification number, the Sodium acetate- • Suitable for both • Requires additive
physician’s name, and the date and time of sample acetic acid- concentration (e.g., albumin
collection. formalin (SAF) procedures and glycerine) for
• Label on the outer sides of container with permanent ink preparation of adhesion of
permanent specimens to
FIXATIVES AND PRESERVATIVES stained smears slides
PRESERVATIEVS ADVANTAGES DISADVANTAGES • Easy to prepare • Permanent stains
10% Formalin • All-purpose • Not Suitable for • Long shelf life not as good as
fixative some permanent • Suitable for acid- with PVA or
• Easy to prepare smears stained fast, safranin, Schaudinn’s
• Long shelf life with trichome and chromotrope fixative
• Good • Inadequate stains
preservative of preservation of • Compatable with
morphology of morphology of immunoassay
helminth eggs, protozoan kits
larvae, trophozoites Schaudinn’s • Good • Less suitable for
protozoan cysts, • Can interfere with Fixative preservation of concentration
and coccidia PCR, especially morphology of procedures
• Suitable for after extended protozoan • Contains mercuric
concentration fixation time trophozoites and chloride
procedures and cysts • Inadequate
UV fluorescence • Easy preparation preservation of
microscopy of permanent morphology of
• Suitable for acid- stained smears helminth eggs and
fast, safranin, larvae, coccidia,
and and microsporidia
chromotrope • Poor adhesion of
stains liquid or mucoid
• Compatible with specimens to
immunoassay slides
kits and UV Modified PVA • Permanent • Staining not
fluorescence copper or zinc smears can be consistent
microscopy made and • Organism
Merthiolate- • Components • Not suitable for stained with morphology may
iodine- both fix and some permanent trichome be poor
formaldehyde stain organisms smears stained • Zinc is preferred • Copper-
(MIF) • Easy to prepare with trichrome over copper morphology of
• Long shelf life • Inadequate • No mercuric cysts and
• Useful for field preservation of chloride trophozoites is
surveys morphology of poor
• Suitable for protozoan • Zinc-better
concentration trophozoites morphology but
procedures • Iodine interferes not comparable
with other stains to LV-PVA
and fluorescence One-Vial • Concentrate and • Certain one-vial
• Iodine may cause Fixatives (such permanent fixatives must use
distortion of as Ecofix, smear can be certain stains
protozoa • Color difference of
Parasafe, Unifix, made out of one
stain
Low viscosity • Good • Inadequate Proto-fix, STF, vial • Staining not always
polyvinyl- preservation of preservation of and others that • Immunoassays consistent
alcohol (LV-PVA) morphology of morphology of may be can be done on • Sometimes more
protozoan helminth eggsand available) most expensive than
trophozoites and larvae, coccidia, • No mercuric formalin and LV-PVA
cysts and microsporidia chloride

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CLINICAL PARASITOLOGY - PRELIMS

MACROSCOPIC EXAMINATION Concentration Technique

• A stool sample submitted to the laboratory should be • These techniques use differences in specific gravity and
screened for gross abnormalities. A freshly passed stool centrifugation to separate the parasites from the fecal
is the ideal specimen for accurate fecal examination debris and increase their recovery.
• Note the color and consistency of the stool. Color may • In sedimentation techniques, parasites are concentrated
help to indicate if the patient is on antibiotic therapy, in the sediment of the tube following centrifugation and
undergone special procedures, or if the patient the sediment is examined microscopically. In flotation
consumed foods that may affect the color of the stool. techniques, the parasites are less dense than the
Consistency indicates the possible stages of the parasite solutions used and, during centrifugation, they float to
that is present in the sample. the surface.
• Examine the surface of the stool if there are tapeworm
proglottids and adult worms. Formalin-Ethyl Acetate Sedimentation Procedure
• Stool specimen should be broken up with an applicator • The most widely used sedimentation technique
stick to check for the presence of adult worms. • The principle of this technique is based on specific gravity
• Note the presence of blood, mucus, and pus • Ethyl acetate is added to a saline-washed formalin-fixed
• Fresh bright red blood suggests acute lower sample and the tube is then centrifuged.
intestinal bleeding or irritation. • Parasites are heavier than the solution and settle in the
• Bloody stool with mucus indicates amebic sediment of the tube, whereas fecal debris is usually
ulcerations in the large intestine or colon. lighter and rises to the upper layers of the test tube.
• ADVANTAGE: Provides good recovery of most parasites
and is easy to perform.
• DISADVANTAGE: Preparation contains more fecal debris
than a flotation technique and is more challenging to the
microscopist.

Zinc Sulfate Flotation Technique

• Also based on differences in specific gravity between the
sample debris, which in this case is heavy and sinks to the
bottom of the test tube, and potential parasites, which
are lighter and float toward the top of the tube.
• Zinc sulfate specific gravity of 1.18 to 1.20, is used as the
concentrating solution.
• ADVANTAGE: More fecal debris is removed and it yields
a cleaner preparation, making it easier for microscopic
examination.
• DISADVATAGE: Some helminth eggs are very dense and
will not float; therefore, some parasites will be missed.
• It is recommended that if laboratories perform this
• A routine microscopic examination of stool specimen technique, they examine saline and iodine preps made
involves several distinct steps: ocular micrometer from the sediment microscopically, as well as the surface
calibration, processing of stool samples, and microscopic film, so as not to miss any parasites.
examination.
III. PERMANENT STAINS
I. OCCUMLAR MACROMETER CALIBRATION • the final procedure in the O&P examination is the
• A calibrated ocular micrometer is necessary whenever a preparation.
microscopic examination is being done. In a differential • Defined as a microscope slide that contains a fixed
diagnosis, it is important to measure size differences of sample that has been allowed to dry and subsequently
various organisms. Parasites are in microns (ù). stained
• There are some protozoa that only possess a trophozoite
II. PROCESSING OF STOOL SAMPLE stage and will not be detected in the concentrated wet
1. Direct Fecal Smear/Direct Wet mount mount preparation. Dientamoeba fragilis is one example
2. Concentration Technique and, if a permanent stained smear is not performed, this
parasite will likely be missed.
Direct Fecal Smear/Direct Wet Mount • Not the method of choice for the identification of
• Mixing a small portion of unfixed stool (stool with no helminth eggs or larvae because these parasites often
added preservatives) with saline or iodine stain too dark or appear distorted.
• Detect the presence of motile protozoan trophozoites. • Helminth eggs or larvae are best detected and identified
• Other parasite stages that might be observed in a direct using a concentration technique.
wet preparation include protozoan cysts, oocysts,
helminth eggs, and larvae however yield is low. Wheatly Trichome
• Direct saline wet preparation-placing a drop of 0.85% • The most widely used permanent stain
saline on a glass slide (a 3- × 2-inch size is suggested) and • Laboratory technicians choose this stain because it uses
mixing with a small portion of unfixed stool using a reagents with a relatively long shelf life and the
wooden applicator stick or another mixing tool. procedure is easy to perform
• Direct iodine wet preparation may be made to enhance
the detail of protozoan cysts.
• (Lugol’s or D’Antoni’s formula)
• Iodine kills trophozoites

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CLINICAL PARASITOLOGY - PRELIMS
o Systemic or blood-borne parasitic infections
are diagnosed by demonstrating the diagnostic
stage(s) of the responsible parasite(s) in a blood
specimen. Parasites that may be recovered in
blood include Leishmania donovani and
Trypanosoma spp., Plasmodium and Babesia
spp., and microfilariae.
o Trypanosoma spp. and microfilariae- observing
motility in a wet preparation
o Definitive identification in a permanent stained
smear. Blood smears can be prepared from
fresh whole blood without anticoagulant
(fingertip or earlobe) or from venipuncture
collection with anticoagulant.
o Blood from fingertip or earlobe
o If malaria is suspected, it is best to prepare
Iron Hematoxylin smears within 1 hour of collection, because
• Reveals excellent morphology of the intestinal protozoa. storage of blood for a longer period leads to
In some cases, the nuclear detail of these organisms is distortion and possible loss of malarial
considered to be stained clearer and sharper than when parasites.
stained with trichrome. o Thick and thin blood smears and stain for
Malaria identification.
IV. STOOL SCREENING METHODS o Wright’s stain and Giemsa stain (preferred).
• Alternative tests have been developed that are often o Knott Technique- The Knott technique is
referred to as rapid methods, or stool-screening designed to concentrate blood specimens
methods. These methods can be obtained as kits that suspected of containing low numbers of
contain monoclonal antibody. microfilariae.
• This commercial antibody is used to detect antigens in o Buffy Coat Slides - A buffy coat is a layer of
patient specimens. Current assays include enzyme white blood cells between the plasma and red
immunoassay (EIA), direct fluorescent antibody (DFA), blood cells that results from centrifuging whole
and membrane flow cartridge techniques. blood. Buffy coat cells may be extracted from
• Some of the kits require fresh or frozen stool and cannot blood specimens, stained with Giemsa stain,
be done on preserved specimens and microscopically examined for Leishmania
and Trypanosoma. Wintrobe tube, and spinning
OTHER INTESTINAL SPECIMENS it for 30 minutes at 100 × g.
1. Duodenal Material o Cultures of blood - one such culture technique
a. Collected by nasogastric intubation or by the that yields favorable results for the recovery of
enteric capsule test (Enterotest). Giardia Leishmania spp. and Trypanosoma cruzi uses
intestinalis trophozoites, Cryptosporidium Novy-MacNeal-Nicolle (NNN) medium.
spp., Isospora belli, Strongyloides stercoralis • Cerebrospinal Fluid and Other Sterile Fluids
and eggs of Fasciola hepatica or Clonorchis o Cerebrospinal fluid (CSF) specimens may be
sinensis. collected for the diagnosis of amebic conditions
b. If (>2 mL), it should be centrifuged and the associated with select ameba as well as African
sediment examined. sleeping sickness.
c. Mixed with PVA fixative; prepared using o A wet preparation can be prepared to search
trichrome, iron hematoxylin, and/or modified for the presence of the characteristic
acid-fast stain. The material can also be used to morphologic forms of Naegleria fowleri and
perform antigen tests for Cryptosporidium Acanthamoeba spp. and the trypomastigote
and/or Giardia. stages of Trypanosoma spp.
d. The Enterotest is a simpler method for o Giemsa, trichrome, and modified trichrome
collecting duodenal material without requiring stains.
intubation. The patient swallows a gelatin o Cultured on non-nutrient agar seeded with
capsule that contains a coiled length of yarn. Escherichia coli. The CSF sediment is inoculated
2. Sigmoidoscopy Material to the medium, sealed, and incubated at 35° C.
a. Examination of sigmoidoscopy (colon) material o Sterile fluids other than CSF include several
is often helpful for detecting E. histolytica. specimen types, such as fluid present in cysts,
Material from ulcers obtained by aspiration or aspirates, peritoneal fluid, pleural fluid, and
scraping should be examined by direct wet bronchial washings.
preparations and permanent stains. • Tissue and Biopsy Specimens
3. Cellophane Tape Preparation o Recovery of a intracellular organisms such as
a. At night, when the body is at rest, pregnant Leishmania spp. and T. gondii.
adult female worms exit the host, typically a o Other parasites that may be detected in these
child, through the rectum and lay numerous samples include free-living ameba,
eggs in the perianal region. Therefore, it is Trypanosoma spp., Trichinella spiralis and
important that the specimen be collected in microsporidia.
the morning before the patient washes or o Hepatic abscess material- suspected of liver
defecates. abscesses caused by E. histolytica
• Sputum
OTHER SPECIMENS AND LABORATORY TECHNIQUE
• Blood

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CLINICAL PARASITOLOGY - PRELIMS
o Sputum - lung fluke Paragonimus westermani, o The Acanthamoeba cysts stain apple green. It is
patients with Strongyloides stercoralis. important to note that this technique does not
o Hyperinfection will demonstrate motile larvae stain the trophozoites
in their sputum. o Scrapings may be processed using histologic
o Microsporidia, E. histolytica, Entamoeba methods.
gingivalis, Ascaris lumbricoides, and o T. gondii, microsporidia, and Loa loa
hookworm. • Mouth Scrapings and Nasal Discharge
o An early-morning specimen is best and should o Mouth scrapings are the sample of choice for
be collected into a widemouthed container the detection of E. gingivalis and Trichomonas
with a screw cap lid tenax
• Urine and Genital Secretions o Nasal discharge -N. fowleri.
o Specimen of choice for the detection of o Wet preps and permanent stains
Schistosoma haematobium eggs and may also • Skin Snips
yield Trichomonas vaginalis trophozoites o Useful in the detection of Onchocerca volvulus
(Vaginal and urethral specimens). o The objective of both procedures is to obtain
o Microfilariae- with a heavy filarial infection. skin fluid without bleeding.
o Should be centrifuged on arrival at the
laboratory. Identify microscopically. REPORTING OF RESULTS AND QUALITY CONTROL
o Permanent stains • Postanalytic phase of laboratory testing. When reporting
o Alternative techniques for the diagnosis of T. a positive specimen, the report should state the scientific
vaginalis include antigen detection methods name (genus and species), along with the stage that is
using latex agglutination and EIA procedures. present (e.g., cyst, trophozoite, larvae, eggs, adults).
o Culture methods are available. • It is also helpful to report the presence of certain cells in
• Eye Specimens the specimen. White blood cells should be reported
o Acanthamoeba keratitis is best diagnosed by semiquantitatively—rare, few, moderate, many. The
the collection and examination of corneal results of the O&P procedure should include a comment
scrapings and be kept moist with sterile saline. indicating that this procedure does not detect
o Cultured on an agar plate seeded with gram- Cryptosporidium spp., Cyclospora cayetanensis, and
negative bacteria. (Examining the culture plate microsporidia.
under low dry magnification every day for 1 • Quantation - Blastocystis homini, helminth eggs,
week should reveal the trophozoites (usually in including Trichuris trichiura, Clonorchis sinensis and
less than 4 days) and the cysts (in 4 to 5 days). Schistosoma spp. and Plasmodium and Babesia spp.
o Scrapings may be transferred to glass slides and • Charcot-Leyden crystals are also reported when found
stained using the calcofluor white stain, and can be quantitated.
followed by microscopic examination using
fluorescent microscopy.

LAB ACTIVITY NO. 3: MACROSCOPIC EXAMINATION

Once a stool specimen has been received in the Fecal Odor
laboratory, the analytic phase of laboratory testing also referred to 1. Normal - peculiar, offensive but not excessively foul. This
processing begins. In this phase, samples are examined from two is principally due to indole and Skatole which are
perspectives, macroscopic and microscopic products of intestinal putrefaction. Offensive odor is
Stool specimen submitted tor parasitic study should first accentuated when diet consists largely of meat
be examined macroscopically to determine the consistency and 2. Extremely foul odor - Occurs in alkaline stool. Suggest
color of the sample. The specimen should be screened and some form of ulceration in the intestines or rectum,
examined for the presence of gross abnormalities especially it due to malignancy, syphilis, or gangrenous
dysentery
Frequency 3. Putrid - found in ulcerated and malignant tumors of the
One or two stools in 24 hours may be considered normal, lower bowel (sigmoid or rectum) and in large
yet one in three or four days is common among healthy persons. hemorrhages.
The individual habit should be considered in every case. 4. Sour or rancid -indicates gas formation, fermentation of
carbohydrates, unabsorbed fatty acids and in high acidity
Fecal Color
1. Brown - normal color is due to urobilin (stercobilin), a Fecal Consistency
reduction product of bilirubin. Diet and drugs can cause 1. Well-formed – normal
marked changes in stool color 2. Abnormal Consistency
2. Black or Tarry (melena) - upper gastrointestinal bleeding a. Pale, bulky or frothy - poor fat digestion
iron therapy, charcoal, bismuth, digested blood b. Hard -constipation
3. Red - lower gastrointestinal bleeding. Pyridium c. Flattened and ribbon-like - Obstruction in the
compounds, beets and food coloring rifampin, bleeding lower bowel
low down in the intestinal tract d. Semisolid - Digestive upset, mild diarrhea or
4. Pale Yellow, White, Gray - Bile duct obstruction, barium after taking laxative
5. Yellow - Milk, diet, corn meal, rhubarb, Senna, santonin, e. Watery - Bacterial infection or after taking
fats purgative
6. Green - Biliverdin, green vegetables, antibiotics, spinach, f. Rice watery stools - Cholera
calomel, cooked greens unchanged biliverdin, meconium, g. Rounded scybalous masses -prolonged
and porphyrins constipation; ball-shaped. "Sybala" means
7. Bulky pale/ Frothy/ Foamy -steatorrhea goat-droppings.

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CLINICAL PARASITOLOGY - PRELIMS
h. Small caliber stools - constipation. If very large ross abnormalities possibly found in stool include adult worms,
in children, it indicates "Hirschsprungs disease proglottids, pus, and mucus. First, the surface of the stool should
be examined tor parasites. The sample should then be broken up -
BRISTOL STOOL CHART a wooden applicator stick works nicely for this task - and examined
once more for macroscopic parasites, especially adult helminths

Other macroscopic abnormalities in the specimen may have

parasitic indications. For example, blood and/or mucus in loose or
quid stool may sug8est the presence of amebic ulcerations in the
large intestine. Bright red on the surface of a formed stool is usually
associated with irritation and bleeding

---end ---

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