Parasitology: protozoa

45 Kerala PSC Lab Technician Gr II practice questions on Parasitology: protozoa, part of Microbiology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
Which of these intestinal protozoa is a flagellate?
1. ABalantidium coli
2. BCryptosporidium parvum
3. CEntamoeba histolytica
4. DGiardia lamblia
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Answer: D · Giardia lamblia
Giardia lamblia (G. duodenalis) belongs to the flagellates (Mastigophora); its trophozoite has four pairs of flagella and a ventral sucking disc. Entamoeba is an amoeba that moves by pseudopodia, Balantidium is a ciliate, and Cryptosporidium is a coccidian (Apicomplexa). Other flagellates of medical importance are Trichomonas, Leishmania and Trypanosoma.
- A: Balantidium coli is a ciliate, the only ciliate parasite of humans.
- B: Cryptosporidium is a coccidian (sporozoan) and has no flagella.
- C: Entamoeba is an amoeba (Sarcodina) that moves by pseudopodia.
Question 2 · Easy
Which form of Entamoeba histolytica is infective to humans?
1. ATrophozoite
2. BUninucleate cyst
3. CMature quadrinucleate cyst
4. DMetacystic trophozoite
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Answer: C · Mature quadrinucleate cyst
Humans are infected by swallowing mature four-nucleated cysts in food or water contaminated with feces. The cyst wall resists gastric acid; in the small intestine each cyst excysts and divides to give eight small metacystic trophozoites, which grow and live in the colon. Trophozoites passed in dysenteric stool die quickly outside the body and are not infective. Cyst passers without symptoms are therefore the main source of spread.
- A: Trophozoites die quickly outside the body and are destroyed by gastric acid.
- B: Uninucleate cysts are immature; they become infective only when they reach four nuclei.
- D: Metacystic trophozoites arise inside the intestine after excystation.
Question 3 · Medium
Tissue cysts of Toxoplasma gondii in brain and muscle contain slowly multiplying:
1. ABradyzoites
2. BTachyzoites
3. CSporozoites
4. DMerozoites
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Answer: A · Bradyzoites
In the acute stage, tachyzoites multiply rapidly in many cell types. As immunity develops, the parasite forms tissue cysts in the brain, eye and muscle, filled with slowly dividing bradyzoites. These cysts persist for life and can reactivate when immunity falls, as in AIDS, causing encephalitis. Sporozoites are found inside sporulated oocysts from cat feces.
- B: Tachyzoites are the rapidly dividing forms of acute infection.
- C: Sporozoites are found inside oocysts shed by cats.
- D: Merozoites form in the cat's intestine during schizogony.
Question 4 · Easy
Which finding is NOT expected in a thin blood film with Plasmodium falciparum?
1. AMaurer's clefts
2. BSchüffner's dots
3. CAccolé (appliqué) forms
4. DCrescent-shaped gametocytes
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Answer: B · Schüffner's dots
Schüffner's dots are fine red stippling in enlarged red cells infected with P. vivax or P. ovale. P. falciparum infects red cells of all ages without enlarging them; its features are delicate rings, often several per cell or at the cell edge (accolé forms), coarse Maurer's clefts and banana-shaped gametocytes. Late stages are rarely seen in peripheral blood. Recognising these features matters because falciparum malaria can become severe quickly.
- A: Maurer's clefts are typical of P. falciparum.
- C: Accolé forms at the edge of the red cell are typical of P. falciparum.
- D: Crescent-shaped gametocytes are diagnostic of P. falciparum.
Question 5 · Hard
A 30-year-old migrant worker from Bihar, now in Kerala, has had fever for 3 months, a massive spleen and pancytopenia. Platelets are 35,000/µL (reference 150,000-400,000/µL) and the prothrombin time is 6 seconds longer than control. Which specimen should be collected to look for LD bodies?
1. APeripheral blood thin film
2. BSkin slit smear
3. CSplenic aspirate
4. DBone marrow aspirate
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Answer: D · Bone marrow aspirate
Fever, massive splenomegaly and pancytopenia in a person from Bihar suggest visceral leishmaniasis. Splenic aspirate has the highest yield (over 95%), but it can cause fatal bleeding and is avoided when platelets are below about 40,000/µL or the prothrombin time is more than 5 seconds longer than control. Bone marrow aspirate is safe and shows LD bodies in roughly 60-85% of cases. A blood film is far less sensitive, and skin smears are used for post-kala-azar dermal leishmaniasis.
- A: LD bodies are scanty in peripheral blood, so a thin film is insensitive.
- B: Skin slit smears are used for post-kala-azar dermal leishmaniasis, not active kala-azar.
- C: Splenic puncture is unsafe with a low platelet count and a prolonged prothrombin time.
Question 6 · Medium
A 30-year-old man has chronic, foul-smelling, greasy diarrhea, but three stool examinations are negative. In suspected giardiasis, which specimen may still show trophozoites?
1. ADuodenal aspirate or a string test
2. BA peripheral blood film
3. CPus from a liver abscess
4. DA midstream urine sample
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Question 7 · Medium
Schizonts of Plasmodium falciparum are rarely seen in peripheral blood films because:
1. ASchizonts break up when the film is fixed
2. BInfected red cells stick in deep capillaries
3. CSchizonts change into gametocytes in blood
4. DSchizogony takes place only in the liver
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Question 8 · Medium
Which form of Leishmania donovani is found in the sandfly gut and in NNN culture?
1. AAmastigote
2. BPromastigote
3. CTrypomastigote
4. DEpimastigote
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Question 9 · Easy
Which animal is the definitive host of Toxoplasma gondii?
1. APig
2. BHuman
3. CCat
4. DDog
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Question 10 · Hard
A 42-year-old man has fever, right upper quadrant pain and a single liver abscess. Stool microscopy is negative. Thick, chocolate-brown pus is aspirated. Which portion of the aspirate is most likely to show Entamoeba histolytica trophozoites?
1. AThe first portion, from the abscess centre
2. BThe last portion, from the abscess wall
3. CA portion kept overnight at 4 °C
4. DAny portion, as amoebae are spread evenly
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Question 11 · Hard
A 25-year-old with falciparum malaria has 45 infected red cells among 1,500 red cells counted on a thin film. His red cell count is 4.0 million/µL. What is the parasite density?
1. A1,200,000/µL
2. B120,000/µL
3. C30,000/µL
4. D12,000/µL
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Question 12 · Hard
A newborn has hydrocephalus, chorioretinitis and intracranial calcification. The mother kept cats during pregnancy. Which result in the baby's blood best confirms congenital toxoplasmosis?
1. AToxoplasma-specific IgG
2. BHigh-avidity Toxoplasma IgG
3. CPositive Sabin-Feldman dye test
4. DToxoplasma-specific IgM
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Question 13 · Medium
Relapses of Plasmodium vivax malaria months after the blood infection has been cleared arise from:
1. ASporozoites resting in the bone marrow
2. BDormant hypnozoites in the liver
3. CGametocytes persisting in the blood
4. DMerozoites hidden in the spleen
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Question 14 · Medium
In patients with AIDS, Cryptosporidium infection can persist and worsen without new exposure because its thin-walled oocysts:
1. AMultiply only inside liver cells
2. BExcyst in the gut and reinfect the host
3. CNeed a cat to complete their cycle
4. DAre destroyed by stomach acid
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Question 15 · Easy
Which insect transmits kala-azar in India?
1. AAedes aegypti
2. BAnopheles culicifacies
3. CPhlebotomus argentipes
4. DCulex quinquefasciatus
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Question 16 · Easy
Which stage of Plasmodium does an infected female Anopheles inject when it bites?
1. AOokinete
2. BMerozoite
3. CSporozoite
4. DGametocyte
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Question 17 · Easy
Band-shaped trophozoites stretched across the red cell are typical of:
1. APlasmodium ovale
2. BPlasmodium malariae
3. CPlasmodium falciparum
4. DPlasmodium vivax
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Question 18 · Easy
How many nuclei does a mature cyst of Entamoeba coli have?
1. ATwo
2. BOne
3. CFour
4. DEight
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Question 19 · Medium
Plasmodium falciparum can reach much higher parasite counts than P. vivax mainly because it:
1. AInvades red cells of all ages
2. BInfects only young reticulocytes
3. CForms hypnozoites in the liver
4. DHas a longer 72-hour cycle
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Question 20 · Medium
An iodine mount of stool from a 6-year-old shows oval cysts about 12 µm long with four nuclei at one end, axonemes and curved median bodies. These are cysts of:
1. AGiardia lamblia
2. BBalantidium coli
3. CEntamoeba coli
4. DEntamoeba histolytica
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Question 21 · Medium
In malaria, man is called the intermediate host because:
1. AMan carries only the sporozoites
2. BThe asexual cycle occurs in man
3. CThe sexual cycle occurs in man
4. DMan cannot infect mosquitoes
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Question 22 · Hard
A routine stool test of a 28-year-old hotel food handler with no symptoms shows round cysts of 12-15 µm with four nuclei and rod-shaped chromatoid bars. No trophozoites are seen. How should the microscopy be reported?
1. AEntamoeba coli cysts
2. BInvasive amoebiasis
3. CE. histolytica/E. dispar cysts
4. DGiardia lamblia cysts
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Question 23 · Medium
A typical serum protein finding in kala-azar is:
1. ALow total globulin with normal serum albumin
2. BRaised albumin with low IgG
3. CNormal globulin with low IgM
4. DRaised IgG with reversed A:G ratio
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Question 24 · Medium
In stool examination for protozoa, a saline mount is examined along with the iodine mount because:
1. ASaline concentrates the cysts and eggs in the sediment
2. BIodine kills trophozoites, so motility is lost
3. CSaline stains the nuclei more clearly
4. DIodine dissolves the cyst walls
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Question 25 · Hard
A 35-year-old man with HIV (CD4 90 cells/µL) has had profuse watery diarrhoea for 6 weeks. Routine saline and iodine mounts are negative. A modified acid-fast smear shows round, pink-red bodies of 4-6 µm. The most likely parasite is:
1. AGiardia lamblia
2. BCyclospora cayetanensis
3. CCystoisospora belli
4. DCryptosporidium parvum
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Parasitology: protozoa

Which of these intestinal protozoa is a flagellate?

Which form of Entamoeba histolytica is infective to humans?

Tissue cysts of Toxoplasma gondii in brain and muscle contain slowly multiplying:

Which finding is NOT expected in a thin blood film with Plasmodium falciparum?

A 30-year-old migrant worker from Bihar, now in Kerala, has had fever for 3 months, a massive spleen and pancytopenia. Platelets are 35,000/µL (reference 150,000-400,000/µL) and the prothrombin time is 6 seconds longer than control. Which specimen should be collected to look for LD bodies?

A 30-year-old man has chronic, foul-smelling, greasy diarrhea, but three stool examinations are negative. In suspected giardiasis, which specimen may still show trophozoites?

Schizonts of Plasmodium falciparum are rarely seen in peripheral blood films because:

Which form of Leishmania donovani is found in the sandfly gut and in NNN culture?

Which animal is the definitive host of Toxoplasma gondii?

A 42-year-old man has fever, right upper quadrant pain and a single liver abscess. Stool microscopy is negative. Thick, chocolate-brown pus is aspirated. Which portion of the aspirate is most likely to show Entamoeba histolytica trophozoites?

A 25-year-old with falciparum malaria has 45 infected red cells among 1,500 red cells counted on a thin film. His red cell count is 4.0 million/µL. What is the parasite density?

A newborn has hydrocephalus, chorioretinitis and intracranial calcification. The mother kept cats during pregnancy. Which result in the baby's blood best confirms congenital toxoplasmosis?

Relapses of Plasmodium vivax malaria months after the blood infection has been cleared arise from:

In patients with AIDS, Cryptosporidium infection can persist and worsen without new exposure because its thin-walled oocysts:

Which insect transmits kala-azar in India?

Which stage of Plasmodium does an infected female Anopheles inject when it bites?

Band-shaped trophozoites stretched across the red cell are typical of:

How many nuclei does a mature cyst of Entamoeba coli have?

Plasmodium falciparum can reach much higher parasite counts than P. vivax mainly because it:

An iodine mount of stool from a 6-year-old shows oval cysts about 12 µm long with four nuclei at one end, axonemes and curved median bodies. These are cysts of:

In malaria, man is called the intermediate host because:

A routine stool test of a 28-year-old hotel food handler with no symptoms shows round cysts of 12-15 µm with four nuclei and rod-shaped chromatoid bars. No trophozoites are seen. How should the microscopy be reported?

A typical serum protein finding in kala-azar is:

In stool examination for protozoa, a saline mount is examined along with the iodine mount because:

A 35-year-old man with HIV (CD4 90 cells/µL) has had profuse watery diarrhoea for 6 weeks. Routine saline and iodine mounts are negative. A modified acid-fast smear shows round, pink-red bodies of 4-6 µm. The most likely parasite is: