LABORATORY DIAGNOSTIC TECHNIQUES
Laboratory diagnosis is a basic step in confirming a clinical diagnosis
of parasitic infection. Different techniques are used for different
specimens. Reliability of the results of an examination depends on the
selected technique carried out. These diagnostic techniques include :
I- Urine examination
II- Stool examination
III- Blood examination
Precautions during preparation of different specimens from
different sources :
-Wear personal protective equipment such as gloves, laboratory
coats.
-If you have cuts or abrasions on the skin of your hands, cover
them with adhesive dressing.
-Remove gloves and wash your hands after completing any task
involving the handling of biological material
-Decontaminate work surface at least once a day
I-URINE EXAMINATION
Urine is produced by the kidney to maintain constant plasma osmotic
concentration; to regulate pH.
Usual colors are colorless,yellow, amber,less commonly pink,red,brown.
Usual appearances (opacity) are clear; less commonly turbid, cloudy and
opaque, unless the specimen has remained at room or refrigerated
temperatures
MICROSCOPIC EXAM.(looking forward cellular element, yeast,
parasite)
Two methods are used, simple and centrifugal sedimentation.
1- Simple Sedimentation :
a. Urine
sample is collected into a conical sedimentation glass
and is left for 30 minutes to sediment.
b. With the aid of a glass pipette, few drops of the bottom sediment
are pipetted onto a clean slide.
c. Spread the urine, apply a cover slip and examine microscopically.
2- Centrifugal Sedimentation :
a. Random urine sample is collected and well mixed.
b. About 10 ml. of urine sample is placed in a centrifuge tube and
centrifuged at 1500 rpm for 5 minutes.
c. The supernatant fluid is discarded.
d. A drop of the sediment is placed on a slide, covered by a cover slip
and examined microscopically.
Some parasitic stages can be detected in urine as S. haematobium
egg, S. mansoni egg, and.
2-STOOL EXAMINATION
Stool specimen :

Examination of fresh specimens permits the observation of
motile trophozoites, but this must be carried out without delay.

Liquid specimens (which are more likely to contain
trophozoites) should be examined within 30 minutes of passage
(not within 30 minutes of arrival in the laboratory!), and soft
specimens (which may contain both trophozoites and cysts)
should be examined within one hour of passage.

If delays cannot be avoided, the specimen should be preserved
in 10 % formalin or PVP (polyvinyl alcohol) to avoid
disintegration of the trophozoites.
Sample preparation:
A- Macroscopic
Examination :
By Naked eye:
o Tape worm segments as T. saginata and T. solium may be found
on or beneath the stool on the bottom of the collection container.
o Ascaris lumbricoides , E. vermicularis
and T. trichiura are
occasionally found on the surface or in the stool.
o Bloody specimens may indicate some parasites, e.g. S. mansoni.
o Soft or liquid stool is highly suggestive of an amoebic infection.
B- Microscopic Examination :
1- Direct Examination :
i- Direct Wet Smear :
Wet smear is prepared by using saline and/or
iodine as working solutions.
▪ Procedure :
a. Place one drop of 0.9% Na Cl on the center of a clean slide .
b. Take about 2 mg. of stool, with an applicator stick, and thoroughly
emulsify it in saline.
c. Cover with cover slip and examine microscopically.
d. A new mount can be prepared with iodine alone.
e. The iodine will stains protozoan cysts for second examination.
The direct saline smear is used mainly to detect motile protozoan
trophozoites. The iodine will kill trophozoites present, thus no motility
will be seen after the iodine is added.
ii- Kato Thick-Smear Technique :
Egg-counts made by this technique is used for the quantitative
diagnosis of helminth infections.
2- Concentration Techniques:
a- Sedimentation Methods: Three methods are of value.
i- Simple Saline Sedimentation:
like urine
ii- Formalin-Ether Sedimentation Technique :
This technique leads to the recovery of all protozoan cysts, and
helminthic eggs and larvae present. Formalin is added for fixation and
preservation of the parasitic stages, while ether is used as an extractor
of debris, fat and oils from the stool. Also, fecal debris absorbs ether
and becomes lighter than the sediment.
iii- Acid-Ether Sedimentation Technique :
The advantage of acids used in this technique is their ability to
dissolve mucus and other substances resulting in cleaner sediment.
b- Flotation Methods:
In contrast to sedimentation, flotation concentrates the eggs and
cysts at the top because their specific gravity is less than that of the
suspending medium.
i- Erlenmeyer’s Method:
ii- Zinc Sulfate Centrifugal Flotation Method :
some helminthic eggs (operculated and un-fertilized Ascaris eggs) will
not float in zinc sulfate but sink to the bottom. So, if zinc sulfate is the
only concentration method used, both the surface film and the sediment
should be examined.
3- Permanent Stained Smears:
Special staining techniques are used as the modified Zeihl-Neelsen
acid-fast stain. This stain is used to differentiate schistosome eggs. The
egg shells of S. mansoni and S. japonicum are acid-fast positive, while
that of S. haematobium are negative.
III- BLOOD EXAMINATION
 The circulating blood is composed of plasma and cells.
 The cells are red cells (or erythrocytes), white cells (or leucocytes)
and platelets.
 Blood cells can be identified in blood films stained with a mixture
of basic and acidic dyes.
 Normal white cells are divided into polymorphonuclear leucocytes
(or granulocytes) and mononuclear cells.
There are three types of granulocyte named according to their staining
characteristics in blood films. They are neutrophils,eosinophils and
basophils. Mononuclear cells are divided into
lymphocytes and
monocytes
 Type of Sample: either
1- Venous blood samples
or
2- capillary blood samples
Venous blood obtained by venipuncture:
1. Label collection tubes and slides with the patient’s name and date
and time of collection.
2. Clean the site well with alcohol; allow to dry.
3. Collect the venous blood in a vacuum tube containing
anticoagulant (preferably EDTA); alternatively, collect the blood in
a syringe and transfer it to a tube with anticoagulant; mix well.
4. Prepare at least 2 thick smears and 2 thin smears as soon as possible
after collection.
Advantage of Venous blood samples :
Provide sufficient material for performing a variety of
diagnostic tests, including concentration procedures (filariasis,
trypanosomiasis).
Disadvantage of Venous blood samples :
In some parasitic diseases (e.g., for diagnosis of malaria),
anticoagulants in the venous blood specimen can interfere with
parasite morphology and staining characteristics.
Capillary blood obtained by fingerstick:
Label slides with the patient’s name and date and time of collection.
1. Clean the site well with alcohol; allow to dry.
2. Clean the area to be punctured with 70% alcohol; allow to dry
3. Puncture the 3rd or 4th finger .
4. Wipe away the first drop of blood with clean gauze.
5. Prepare at least 2 thick smears and 2 thin smears.
Advantage of Capillary blood obtained by fingerstick:
capillary blood samples are preferable in parasitic diseases, in which
anticoagulants in the venous blood specimen can interfere with parasite
morphology and staining characteristics.
A- Preparation of Blood Films:
1- Thin Blood Film:
Procedure:
a- Bring a clean spreader slide, held at a 45° angle, toward the drop of
blood on the specimen slide.
b- Wait until the blood spreads along the entire width of the
spreader slide.
c- While holding the spreader slide at the same angle, push it forward
rapidly and smoothly.
Thin film to be
examined
d- Fix the smears by dipping them in absolute methanol.
2- Thick Blood Film:
▪ Procedure:
a. Place 2 or 3 drops of fresh blood (without anticoagulant) on
a clean slide.
b. Using the corner of a clean slide, mix and spread the drops
of blood in a circle
c. Continue stirring for 30 sec. to prevent the formation of
fibrin strands that may obscure the parasites.
d. Allow the film to air dry at room temperature. No need for
fixation.
e. Before staining, the films are leaked in phosphate-buffered
water for de-haemoglobinization of RBCs.
f. Films are stained with Giemsa stain.
3- Combination of Thin and Thick Blood Films:
In field surveys, it is helpful to prepare slides with both a thick
and a thin blood films on the same slide.
B- Staining of Blood Films:
The most common stains used are Giemsa and Leishman stains.
1- Giemsa Stain:
2- Leishman Stain:
Normal blood Picture :
Practical work:
a-Red blood cells transport oxygen
b-Neutrophils digest bacteria
c-Lymphocytes consist of B cells and T cell
d-Platelets help blood to clot
PRACTICAL HELMINTHOLOGY
A- CLASS : TREMATODA
FASCIOLAE
1- Fasciola gigantica, adult :
-
Length : 3-7 cm.
-
Elongated with parallel borders.
-
Ventral sucker is larger than
oral one.
-
Lateral compound and inner Tor Y-shaped caecal branches.
-
2 branched testes (in tandem).
-
One branched ovary, anterior to
the anterior testis, in the middle
of the body.
-
Numerous vitelline follicles at
the lateral borders.
2- Fasciola hepatica, adult :
a. Length : 2-3 cm.
b. Shorter and broader flat worm
with two converging lateral
borders.
c. Cephalic cone and shoulders
are prominent anteriorly.
d. Oral and ventral suckers
are equal.
e. The medial caecal branches are
simple diverticula.
3- Fasciola egg :
- Oval.
-
Thin, operculated shell.
-
Size : 160X80 u.
-
Yellowish-brown.
-
Contains an immature
embryo.
HETEROPHYES HETEROPHYES
1- Adult :
-
Pyriform in shape with broad
posterior end.
-
Size : 1.5-3 mm.
-
3 suckers, oral (small),ventral
(large) and genital.
-
2 simple intestinal caeca.
-
2 oval testes, opposite each other,
posteriorly.
-
Oval mid plane ovary in front of
testes.
-
Few large postero-lateral vitelline
follicles.
2- Egg :
-
Oval.
-
Size : 30X15 u.
-
Yellowish-brown.
-
Thick-shelled.
-
Operculated.
-
Small knob posteriorly.
-
Mature (contains miracidium).
HUMAN SCHISTOSOMES
1- S. haematobium Egg:
-Size: 120 x 60 µ.
-Shape: oval.
-Shell: thin with terminal spine.
-Colour: translucent.
-Contents: mature miracidium.
2- S. mansoni egg:
Size: 140 x 70 µ.
Shape: oval.
Shell: thin with lateral spine.
Colour: translucent.
Contents: mature miracidium.
B- CLASS : CESTODA
TAENIAE
1- T. saginata gravid segment :
a- Longer than broad.
b- Size : 20X7 mm.
c- Main lateral uterine branches : 1520 on each side.
2- T. solium gravid segment :
a- Longer than broad.
b- Size : 11X6 mm.
c- Main lateral uterine branches : 9-11
on each side.
3- Taenia egg :
a- Rounded.
b- 40 u. in diameter.
c- Brownish in colour.
d- With thick double-layer and radiallystriated embryophore.
e- Contains hexacanth embryo.
ECHINOCOCCUS GRANULOSUS
1- Adult :
a- Scolex and 3 segments (immature,
mature and gravid).
b- Scolex : 4 suckers and rostellum
with 2 rows of taenoid hooks.
c- Mature segment contains : posterior
horse-shoe shaped ovary, compact
vitelline gland, closed uterine tube,
numerous testes laterally and
alternate genital pores.
d- Gravid segment : 1/2 body length.
Contains gravid uterus with lateral
pouches filled with ova.
2- Egg:
a- Size: 30-50 u
b- Shape: spheroid with 2
envelopes:
outer egg shell,
-
- inner embryophore with two polar
thickenings from each arises 4-8
filamints.
c- Colour: translucent.
d- Contents: mature hexacanth
embryo.
HYMENOLEPIS NANA
Egg :
-Size: 30-50 µ.
-Shape: spheroid with 2 envelopes:
-outer egg shell,
-inner embryophore with two polar
thickenings from each arises 4-8
filaments.
-Colour: translucent.
-Contents: mature hexacanth embryo.
C- CLASS : NEMATODA
ASCARIS LUMBRICOIDES
Fertilized egg :
Broad oval.
Size : 60X45 u.
Yellowish-brown in colour.
Thick-shelled with regular
albuminous mammillations.
Immature (contains large single cell
stage embryo).
ENTEROBIUS VERMICULARIS
Egg :
a- D-shaped (plano-convex).
b- Size : 50X25 u.
c- Shell : double-walled.
d- Translucent.
e- Contains fully developed larva.
TRICHINELLA SPIRALIS
Trichina capsule :
a- Ellipsoidal in shape.
b- Between muscle fibers.
c- Size : 0.5X0.2mm.
d- Contains coiled larva (1 mm.
long).
ANCYLOSTOMA DUODENALE
egg:
a- size: 60 X40 u.
b- shape: Oval with blunt
poles. Thin shell.
c- Colour: translucent.
d- Contents: immature ovum
(4- cell stage).
(empty narrow space between shell and
contents)
Trichuris trichiura
Egg :
Barrel-shaped.
50X25u.
Thick-shelled with translucent bipolar mucoid plugs.
Yellowish-brown.
Immature (contains an embryo in
the single cell stage).
Wuchereria bancrofti
Microfilaria:
-
300 x10 µ.
-
Smooth ,graceful body curves.
-
Sheathed, the sheath is loose
and redundant.
-
Bluntly rounded anterior end.
-
Tapering posterior end and free
of nuclei.
PROTOZOOLOGY
Entamoeba coli
Cyst:
a- Rounded.
b- 15-25 U. in diameter.
c- Contains 8 nuclei (at different
levels).
d- No chromatoid bodies in mature
cyst.
Entamoeba histolytica
Cyst :
a- Rounded.
b- 10-20 μ in diameter.
c- Contains 4 nuclei (at different levels)
and rod-shaped chromatoid bodies
with rounded ends.
INTESTINAL FLAGELLATES
Giardia intestinalis
Cyst:
a- Oval.
b- Size: 10X5 u.
c- Double-walled.
a- 4 nuclei at one pole.
b- Remnants of axostyles and
parabasal body.
HAEMO-SOMATIC FLAGELLATES
Polymorphic trypanosomes
( T. gambiense, T. rhodesiense):
a- Elongated bodies and multisized (20-30 u. in length).
b- Extra-cellular.
c- Central vesicular nucleus.
d- Posterior kinetoplast.
e- Long undulating membrane.
f- Free flagellum.
Multiple in the blood film.
CLASS: CILIATA
Balantidium coli
Trophozoite :
a- Oval in shape.
b- 100X50 u.
c- Covered with cilia.
d- Anterior cytostome.
e- 2 nuclei :
i- Macronucleus (kidney- shaped).
ii- Micronucleus (rounded).
f- 2 posterior contractile vacuoles
CLASS: SPOROZOA
Plasmodium malariae
1- Ring form:
a- Single ring.
b- Large (fills 1/2 R.B.C.).
c- Enlarged parasitized RBCs.
2- Schizont:
a- Large (fills R.B.C.).
b- Contains 8 (6-12) merozoites
arranged regularly (rosetteshape).
c- Normal size of parasitized
RBCs.
3- Gametocyte :
a- Large (fills R.B.C.).
b- Rounded or oval.
Toxoplasma gondii
Trophozoite:
a- Crescent-shaped.
b- One pole is more rounded than
the other.
c- 6X3 u.
d- Nucleus is eccentric (near the
rounded end).
e- Para-nuclear body (near the
pointed end).
PRACTICAL ENTOMOLOGY
CLASS : ARACHNIDA
SARCOPTES SCABIEI
1- Male :
a- Grey-coloured.
b- Rounded in shape.
c- 4 pairs of legs venterally.
d- Anterior 2 pairs of legs ends with
suckers.
e- 3rd pair of legs ends with long
bristles.
f- 4th pair ends with suckers.
2- Female :
a- Anterior 2 pairs of legs ends
with suckers.
b- Posterior 2 pairs of legs ends
with long bristles.
CASES OF PARASITIC INFECTIONS
A. HELMINTHIC INFECTIONS
CASE 1:
A 29-year-old woman presented to the physician complaining of
diarrhea, mild indigestion, hunger pains, loss of weight and frequent
abdominal pain. She passed white segments, each about 2 cm long,
with or without defecation causing perineal irritation and pruritus. She
is fond of eating roasted meat.
The patient was instructed to submit three stool specimens, on
alternate days that were examined for ova and parasites. Also, blood
sample was drawn for complete blood count.
The blood count revealed eosinophilia (16% eosinophils). On
examination of the concentrated stool sediments, several yellowbrown, spherical, 40 µ in diameter, thick-shelled eggs were detected.
The eggs were characterized by radial striations. Gravid segments
were also detected in the stool specimens; each contained 15-20 lateral
uterine branches, on either side, when stained with an Indian ink.
QUESTIONS:
1. Which parasite is causing the patient's illness?
2. Name the 2 species of this genus which cause human disease.
3. Can they be differentiated by the morphological appearance of
their eggs? Explain.
4. Can these 2 species be differentiated by the appearance of their
proglottids? Explain.
5. Compare the morphological characteristics of the scolices of these
2 species.
6. What is the infective stage? What is the mode of infection?
7. Why is it important to differentiate between these 2 species?
8. How is this infection treated?
9. What is the sure sign of complete cure?
10. How can you control this parasite ?
CASE 2:
A 45-year-old man was presented with pain in the upper quadrant
of the abdomen. He had a history of contact with dogs many years
ago. On examination, the physician noted an enlarged liver with a
palpable mass in the right hypochondrium. The patient was submitted
for stool, blood and radiological (plain x-ray, CT and MRI)
examinations.
Stool examination is negative for ova or parasites. The blood count
revealed eosinophilia (24 % eosinophils). Radiological studies
revealed a rounded space-occupying lesion, 12 cm in diameter in the
liver. Microscopic examination of a biopsy specimen confirmed the
diagnosis of the parasitic infection. During surgical removal of the
hepatic cyst, aspiration of the cyst contents was performed and the
contents were also examined microscopically.
QUESTIONS:
1. Based on the patient's symptoms, which parasitic infection do you
think he has?
2. What aspect of the patient's history is a clue to his infection?
3. Describe the morphology of this cyst.
4. What danger to the patient exists during surgical removal
and aspiration of the cyst?
5. Describe the life cycle of this parasite.
6. Can sputum examination help in the diagnosis?
7. What is the parasitological diagnostic value of Ziehl-Neelsen stain?
8. How would you treat this patient?
9. How can you control this disease?
CASE 3:
A 10-year-old boy was presented to the pediatrician suffering from
headache and gastrointestinal symptoms, including abdominal pain
and persistent diarrhea with associated loss of appetite and weight
loss. A stool sample was sent immediately to the laboratory for
examination for ova and parasites.
Examination of the fresh specimen showed oval, thin-shelled eggs.
Oncospheres having numerous bi-polar filaments were observed
inside the eggs. A proglottid containing eggs is detected.
QUESTIONS:
1. Which parasite is causing this patient's symptoms?
2. Name the 2 species of this genus which cause human disease.
3. Can they be differentiated by the morphological appearance of
their proglottids? Explain.
4. Why is this parasite unusual among members of its class?
5. What is the infective stage(s)?
6. How is this parasite transmitted?
7. How is the diagnosis of this infection made?
8. Describe the different types of the life cycle of this parasite.
9. How is this infection treated?
10.What are the precautions to be followed during treatment of this
parasite?
11.How can you control this infection?
CASE 4:
A 21-year-old woman presented suffering from abdominal colic,
nausea, vomiting and diarrhea. After a physical examination, which
was un-remarkable, the physician ordered a stool analysis for eggs
and parasites.
Microscopic examination of a concentrated wet-mount preparation
revealed several types of eggs. These eggs had thick shells and were
oval, with some being more broadly oval than others. Some eggs
lacked the outer mammillated covering found on the majority of eggs.
The diagnosis of this intestinal parasitic infection was made on the
basis of microscopic analysis of stool specimen.
QUESTIONS:
1. Which parasite would you suspect of causing this patient's
infection?
2. Describe the variable appearance of eggs of this parasite.
3. Which nematodes are most likely to cause human intestinal
infection?
4. What is the infective stage?
5. How is this infection transmitted?
6. Do you think that this patient can transmit this parasitic infection to
other members of the family during food handling? Why?
7. Describe the life cycle of this parasite.
8. Describe the clinical manifestations of this infection.
9. Which complications may cause this infection to be lifethreatening?
10.How is this infection treated and controlled?
CASE 5:
A 7-year-old boy was not sleeping well, had been irritable, and had
complained to his mother about anal itching and irritation. The boy's
younger sibling also began to complain of similar symptoms.
The children were taken to the pediatrician for evaluation. He
ordered a parasitological laboratory test to provide a strict diagnosis. A
worm egg seen microscopically enabled the laboratory to identify the
worm causing the symptoms.
QUESTIONS:
1. Which parasite is causing the children's discomfort?
2. Which type of laboratory procedure would the physician have
ordered to make a diagnosis?
3. How is this procedure performed?
4. What are the precautions to be followed during performing this
procedure?
5. How is the infection transmitted?
6. Describe the life cycle of this parasite.
7. How is the diagnosis made, using this procedure?
8. Which intestinal protozoon has been associated with this
helminthic infection?
9. Should this patient be treated?
10.How is this infection treated?
11.What are the precautions to be followed to eradicate this parasitic
infection?
CASE 6:
A 6-year-old boy presented to the pediatrician suffering from
diarrhea, abdominal pain and nausea. Blood was drawn for complete
blood count. Three stool specimens were collected and submitted for
examination for ova and parasites.
Blood picture revealed hemoglobin of 11.5 gm/dl. Microscopic
analysis of the concentrated stool specimens revealed numerous bilestained, barrel-shaped eggs. The eggs were characterized by having
clear, prominent and protruding bi-polar plugs.
QUESTIONS:
1. Which parasitic ova would fit the description of those detected in
the patient's stool specimens?
2. Describe the morphological characteristics of the adult worms.
3. Which explains the common name of this parasite?
4. What is the infective stage of this parasite?
5. Describe the life cycle of this parasite?
6. What is the main complication of this infection?
7. How is the diagnosis of this infection made?
8. Which other nematode egg may be confused with this parasite?
Can they be differentiated by the morphological appearance?
Describe.
9. How does the patient's blood test results relate to this infection?
10.How is infection with this parasite treated?
11.How is infection with this parasite prevented and controlled?
CASE 7:
A 41-year-old farmer presented with vague gastrointestinal
complains, fatigue, weakness, pallor and loss of weight. The physician
ordered a stool analysis. Three stool specimens, collected on alternate
days, were submitted for examination for ova and parasites. Blood
sample was also drawn for complete blood count.
A moderate number of eggs were detected with occult blood in the
stool. Each is oval, translucent with blunt poles and clear extraembryonic space. A single larva was also observed in one stool
specimen. This specimen had sat overnight at room temperature
before being examined. Hematology result revealed hemoglobin of
10.0 gm/dl.
QUESTIONS:
1. Based on the patient's symptoms and morphology of the detected
eggs, which parasites are possible causes of the patient's
symptoms?
2. Compare the geographical distribution of these 2 parasites.
3. How is this infection transmitted to humans?
4. Describe the life cycle of these parasites.
5. Would you expect to find both eggs and larvae of these parasites in
an infected patient's stool specimen? Explain.
6. Describe the 2 larval stages of these helminths.
7. Which other nematode has larval stages, in the stool that may be
confused with the larvae of these parasites?
8. What are the causes and type of anaemia that may occur in
children heavily infected with these parasites?
9. How is this infection treated?
10.How can you control this parasitic infection?
CASE 8:
A 29-year-old man was living and studying in Damietta. He was
complaining of fever and swelling in the right lower limb 4 years ago.
Clinical examination revealed enlarged right inguinal lymph nodes.
Lymphangitis and lymphoedema was observed in his lower limbs and
his scrotum with thickened spermatic cordThe patient's symptoms, combined with his geographical area of
origin, created a suspicion of a parasitic infection. Blood sample was
drawn and sent to the laboratory for a complete blood count and thin
and thick blood smears.
Eosinophilia (28%) was observed. Blood smears were stained by
Delafield's hematoxylin method and examined microscopically. A few
number of sheathed microfilariae averaging 260 u in length with
bluntly rounded anterior portions, were revealed. A large number of
distinct nuclei were seen in the microfilariae. The nuclei did not
extend to the tips of the tails which tapered to a point.
QUESTIONS:
1. Which parasite is causing this patient's symptoms?
2. How is this infection differentiated from the related helminths?
3. Which insects act as the intermediate hosts for these parasites?
4. Describe the life cycle of this parasite.
5. How is the diagnosis of this infection performed?
6. What is the best time for blood sampling in the diagnosis of this
infection?
7. What is the value of the provocative test in this infection?
8. Describe the morphological characteristics of other sheathed
microfilariae which may be detected in a blood smear.
9. Why was Delafield's hematoxylin stain used?
10. Which drugs may be used to treat this infection?
11. How can we control this parasitic infection?
CASE 9:
A 36-year-old man suffering from intermittent fever, diarrhea,
indigestion and abdominal pain in the right hypochondrium. Upon
examination, he had a slightly enlarged tender liver and yellow
colouration of the sclera. When questioned regarding his eating habits,
the patient admitted to having a fondness for un-cooked water-cress
and raw vegetables. An order was written for stool examination for
ova and parasites. Blood sample was collected for complete blood
count and liver function tests.
Haematology results showed evidence of anaemia and eosinophilia
(60% eosinophils). The patient's liver enzyme levels were slightly
elevated. The diagnosis was made microscopically after the
observation of large, oval, 180X90 u, yellowish-brown, operculated
eggs in the concentrated stool specimen.
QUESTIONS:
1. Which parasite might be causing this infection?
2. Where is this parasite found geographically?
3. Which other helminth lays eggs indistinguishable from the
eggs described in this specimen?
4. How does transmission of this parasite occur?
5. What are the usual symptoms of the disease in humans?
6. How the diagnosis of this infection is usually made?
7. How do you exclude false diagnosis?
8. How this parasite is treated?
9. How can you control such infection?
CASE 10:
A 13-year-old male, from a village near Mansoura, presented to the
Out-Patient Clinic of Mansoura University Hospital with complaints
of painful urination, the presence of blood in his urine, fatigue, fever
and general body aches. Upon examination, the physician ordered a
urine analysis and urine culture to rule out a urinary tract infection.
Culture results were negative for pathogenic bacteria. Microscopic
examination of the urine sediment revealed proteinuria, many RBCs
(haematuria) and few white blood cells. Oval, translucent eggs with
prominent terminal spines were also detected.
QUESTIONS:
1. Which parasite is the cause of this patient's infection?
2. How is this infection transmitted?
3. Describe the life cycle of this parasite.
4. Mention the complications of this parasitic infection.
5. Describe the detected egg.
6. Compare this egg with those of other members of this genus.
7. Which types of specimens should be collected for diagnosis?
8. How is this infection diagnosed?
9. Describe the "hatching test" and mention its value.
10. What is the association of this infection with bladder cancer?
11. How is this infection treated?
12. How is infection with this parasite prevented and controlled?
CASE 11:
A 22-year-old Egyptian woman was visiting American relatives
and developed fever, malaise, dysentery and abdominal pain. Her
relatives brought her to the family doctor for examination. Upon
examination, she was noted to have liver tenderness. Blood was drawn
for complete blood count and liver enzyme analysis. Three stool
specimens were submitted for examination for ova and parasites.
The patient was noted to be mildly anaemic and had slightly
elevated liver enzyme levels. Two of the 3 stool specimens revealed a
small number of eggs. Each is oval, translucent, 140X70 p with a
prominent lateral spine.
QUESTIONS:
1) Which parasite is causing this patient's infection?
2) How does this parasite differ from other human trematode
parasites?
3) Describe the life cycle of this parasite.
4) Give an account on Katayama syndrome?
5) Compare these ova with those of other members of this genus.
6) What are the possible complications of this parasitic infection?
7) How is this infection diagnosed?
8) How is "hatching test" used to determine egg viability?
9) Do bird species in this genus cause human disease?
10)
How is this infection treated?
11)
How can we control such an infection?
B. PROTOZOAL INFECTIONS
CASE 1:
A 22-year-old male college student visited his family doctor
complaining of crampy abdominal pain, malaise, nausea, fever and
bloody mucoid diarrhea. He had been passing 6-8 loose stools daily
for 6 days.
Stool specimens were collected on 3 alternate days and sent to the
laboratory.
The stool culture was negative for pathogenic bacteria. No
parasitic ova were detected in the concentrated sediment of the
specimens. A small number of amoeboid trophozoites, measuring 1525 p in diameter containing single nucleus and few R.B.Cs. in the
finely granular cytoplasm were seen. No cyst forms were observed.
By the permanent trichrome stain, the nucleus has a central karyosome
with fine, regularly distributed peripheral chromatin granules on the
inner surface of the nuclear membrane.
QUESTIONS:
1. Based on the patient's symptoms, which intestinal parasitic
infection do you think he has?
2. What would you suspect the consistency of this patient's stool to
be? Why?
3. How is this protozoon transmitted?
4. Discuss the pathogenicity of amoebiasis.
5. Describe the life cycle of this protozoan parasite.
6. Describe the clinical manifestations of this infection.
7. Describe the ulcers formed in sever cases of amoebic dysentery.
8. What is the cause of diarrhea in intestinal amoebiasis?
9. How do the symptoms of amoebic dysentery mimic those of
bacillary dysentery?
10. Is this parasite capable of causing extra-intestinal infection?
Explain.
11. How should this patient be treated?
12. Discuss the methods of prevention and control of this infection.
CASE 2:
A 19-year-old woman presented to the physician suffering from
profuse watery diarrhea, crampy epigastric pain and foul-smelling
flatulence. The patient was instructed to submit a stool specimen for
routine examination.
Three stool specimens were collected, on alternate days, and
submitted for examination for ova and parasites. A wet mount and
permanent trichrome stain microscopic examination revealed a small
number of oval trophozoites, measuring 12X6 p. The structure of this
trophozoite gave the overall appearance of "smiling face". Some cysts,
having 4 nuclei, the characteristic median bodies and longitudinal
fibers were also seen.
QUESTIONS:
1. Which protozoan parasite is causing this infection?
2. Which form of this parasite is infectious? Draw it.
3. How does the structure of these trophozoites account for the
"smiling face”?
4. Name the habitat of this parasite.
5. How is this parasite transmitted?
6. How does this parasite attach itself to the intestinal wall?
7. Which condition might result as a sequence of this attachment?
8. Describe the life cycle of this parasite?
9. Describe the pathogenicity of this protozoon.
10.How is the laboratory diagnosis of this infection made?
11.What is the value of the duodenal aspirate in the diagnosis of this
infection?
12. How is this infection treated?
13. How can this infection be prevented and controlled?
CASE 3:
A 39-year-old man resented to the physician suffering from persistent
night sweats, headache, intermittent fever and chills, which occurred
approximately every 48 h. Clinical examination revealed high
temperature (39.6° C), low pulse rate (65/min.), soft palpable spleen
and tinge of jaundice. Blood was drawn for laboratory studies
including complete blood count, thin and thick smears for parasites.
The patient was slightly anaemic, with a hemoglobin level of 9.5
gm/dl. Examination of Giemsa-stained blood films revealed the presence
of an enlarged R.B.Cs. containing trophozoite stages. Several irregular
amoeboid
trophozoites
containing
brown
granules
were
seen.
Eosinophilic stibbling was visible in the cytoplasm of the RBCs. A few
round to oval gametocytes were seen. Based on these findings, a
diagnosis of infection with a blood parasite was made.
QUESTIONS:
1. Which parasite is infecting this patient?
2. Which disease does this patient have?
3. Describe the morphological characteristics of the parasitic stages
which may be detected in thin Giemsa-stained smears.
4. Name the species and the types of diseases caused by these species.
5. Comment on the size of parasitized R.B.Cs. in infection with the
different species of this genus.
6. Describe the clinical manifestations caused by this parasite.
7. Which serious complications may occur with this infection?
8. How does the life cycle of different species of this parasite vary?
9. When should blood be collected, when this infection is suspected?
10. Why should thin and thick blood films be ordered to diagnose this
disease?
11. In addition to thin and thick blood smears, which other laboratory
tests are available for to diagnose this infection?
12. How would this patient be treated?
13. Differentiate
between
the
types
of
recurrence
(relapse
and recrudescence) of this disease. What are the causes of each?
CASE 4:
A 33-year-old man with AIDS had been suffering from headache,
fever and fatigue for several weeks. He also had a history of
disorientation, confusion and convulsive attacks.
Serological tests for Toxoplasma-specific immunoglobulin M were
negative. A computed tomography (CT) revealed multiple cerebral
lesions. After being treated with a combination of pyrimethamine and
sulfonamide, the patient appeared to recover from the infection.
QUESTIONS:
1. What is the likely diagnosis of this patient's parasitic illness?
2. What is the association between the patient's history of AIDS and
his infection?
3. Which other group of individuals is at risk when infected with this
parasite?
4. How is this infection transmitted?
5. Describe the infective sage(s), to man, of this protozoon.
6. Describe the life cycle of this parasite.
7. Why was serology negative for this patient?
8. How is the diagnosis of this infection made?
9. How can this infection be prevented and controlled?