Parasitology (Protozoa, Plasmodium, Helminths, Nematodes, Cestodes, Trematodes) MCQs

Microbiology · 101 free questions with answers & explanations.

1. A 28-year-old traveler from sub-Saharan Africa presents with fever every 48 hours, severe anemia, and peripheral blood smear showing ring forms and banana-shaped gametocytes. No Schüffner's dots are seen. Which Plasmodium species is responsible?
2. A 5-year-old presents with perianal pruritus worse at night. Scotch tape applied perianally shows D-shaped (one side flattened) eggs. The mode of transmission of this parasite is:
3. A patient with epilepsy of new onset has multiple ring-enhancing cystic lesions in the brain on MRI with a scolex visible in one lesion. He works on a pig farm and lives in a rural area with poor sanitation. The condition is:
4. A 40-year-old Egyptian man presents with painless hematuria. Cystoscopy shows bladder granulomas. Urine microscopy reveals eggs with a terminal spine. The intermediate host of the causative parasite is:
5. A 25-year-old from Bihar develops prolonged fever, hepatosplenomegaly, and weight loss. Bone marrow aspirate shows macrophages filled with small intracellular organisms. The vector responsible for transmission is:
6. In Plasmodium falciparum malaria, cytoadherence of infected erythrocytes to vascular endothelium and rosette formation with uninfected erythrocytes is mediated by which parasite-derived ligand expressed on the erythrocyte surface?
7. A 30-year-old migrant worker presents with periorbital edema, myalgia, fever, and eosinophilia after eating undercooked pork. Muscle biopsy shows coiled larvae within a nurse cell. The nurse cell is formed from:
8. Leishmania donovani evades intracellular killing inside macrophages primarily by which mechanism?
9. A child from rural Bihar is found to have Taenia solium cysticerci in the brain on MRI. The definitive diagnosis of neurocysticercosis is BEST confirmed by detecting antibodies against which antigen in serum or CSF?
10. Plasmodium falciparum causes more severe malaria than other species partly due to cytoadherence. The parasite ligand responsible for binding to ICAM-1 on cerebral endothelial cells is:
11. A patient from Bihar presents with fever, splenomegaly, and pancytopenia. Bone marrow aspirate shows amastigotes within macrophages. The organism evades macrophage killing by inhibiting:
12. A 6-year-old child presents with passage of a proglottid in stool. Microscopy shows a proglottid with a uterus containing >13 lateral branches on each side. The most likely organism and risk of cysticercosis in this case is:
13. A patient undergoes colonoscopy showing adult worms with a prominent buccal capsule containing cutting plates. The laboratory diagnosis of iron deficiency anemia in this patient is BEST confirmed by:
14. Entamoeba histolytica causes liver abscess. The virulence factor that enables this organism to lyse hepatocytes and evade complement is:
15. A patient with falciparum malaria develops severe haemolysis, haemoglobinuria, and acute kidney injury within hours of receiving primaquine. Which enzyme deficiency is responsible for this complication?
16. In the laboratory diagnosis of visceral leishmaniasis (kala-azar), which of the following has the highest sensitivity and is considered the gold standard method?
17. Cyclosporiasis caused by Cyclospora cayetanensis is differentiated from Cryptosporidium parvum infection on stool examination by which characteristic feature?
18. A 35-year-old fisherman from Bihar presents with abdominal pain and passage of proglottids in stool. Proglottid examination shows more than 15 lateral uterine branches on each side. The most likely diagnosis and appropriate treatment are:
19. A traveller from South America presents with unilateral periorbital oedema (Romaña's sign), fever, and hepatosplenomegaly. Trypomastigotes with a large kinetoplast are seen on blood smear in a C/U shape. Laboratory tests to confirm the diagnosis include:
20. A patient from Assam presents with fever and is found to have thick blood films showing 'banana-shaped' gametocytes. Thin films reveal infected erythrocytes with 'appliqué (accolé) forms' and multiple ring forms per cell. PCR confirms the species. Which diagnostic marker distinguishes this species from P. vivax in antigen-based rapid diagnostic tests?
21. Strongyloides stercoralis is unique among intestinal nematodes in its ability to cause hyperinfection syndrome in immunocompromised hosts. What is the key mechanism enabling this autoinfection?
22. A child with epilepsy and ring-enhancing CNS lesions on MRI undergoes serology. EITB (enzyme-linked immunoelectrotransfer blot) using lentil-lectin purified glycoproteins is positive. Which parasite is responsible and which larval form is involved in the CNS lesion?
23. In diagnosis of visceral leishmaniasis (kala-azar), which serological test uses a recombinant antigen rK39 and has highest sensitivity and specificity for field diagnosis in India?
24. Paragonimus westermani (lung fluke) infection is acquired by eating raw or undercooked crabs or crayfish. Which intermediate hosts are involved in the life cycle and what is the infective stage for humans?
25. A patient with Plasmodium vivax malaria is started on primaquine for radical cure. Prior to initiating treatment, testing for G6PD deficiency is mandatory because primaquine undergoes hepatic metabolism to reactive oxygen species that preferentially damage:
26. In the laboratory diagnosis of visceral leishmaniasis, the rK39 immunochromatographic strip test detects antibodies against a recombinant antigen derived from which part of Leishmania donovani?
27. Cysticercus cellulosae infection in the human CNS elicits which primary immunological response that forms the basis of serology-based diagnosis using EITB (enzyme-linked immunoelectrotransfer blot)?
28. Wuchereria bancrofti microfilariae exhibit nocturnal periodicity in blood. This periodicity is explained by which physiological mechanism?
29. A stool examination shows eggs with a characteristic lateral spine. The most appropriate treatment for this infection, and its mechanism of action, is:
30. A patient from northeast India presents with fever, splenomegaly, anaemia, and hypergammaglobulinaemia. Peripheral smear shows large mononuclear cells. Direct agglutination test (DAT) is positive. Bone marrow aspiration reveals amastigotes within macrophages. What is the mechanism by which the causative organism evades macrophage killing?
31. A 25-year-old woman from Maharashtra presents with recurrent P. vivax malaria despite completing chloroquine treatment for acute attacks. She continues to relapse every 3 months. Which drug prevents relapse by eradicating the dormant hepatic form?
32. On examination of a stool sample, eggs with a rounded operculum, prominently shouldered operculum, and a small knob at the abopercular end are seen. The patient reports eating freshwater fish in the Assam region. Which fluke is responsible?
33. A 35-year-old presents with cystic lesion in the liver on ultrasound. Serological tests (ELISA) are positive for Echinococcus antigen. Casoni's skin test shows immediate-type hypersensitivity. Which cell type is responsible for the eosinophilia seen in this patient?
34. Examination of CSF from a patient with meningo-encephalitis shows a thick-walled cyst with scolex, hooklets, and calcareous corpuscles. The scolex shows four suckers and a rostellum with hooks. Serology is positive for T. solium antibody. What is the diagnostic stage found in CSF and how did the patient acquire CNS disease?
35. A patient with confirmed Plasmodium vivax malaria is treated with chloroquine but returns 3 weeks later with another febrile episode. Blood film again shows P. vivax rings. Which mechanism BEST explains this relapse rather than re-infection?
36. A 30-year-old woman from Kerala presents with lymphoedema of the right leg, episodic adenolymphangitis and chyluria. Microfilaria are found in a midnight blood sample. Which feature on microscopy would BEST differentiate Wuchereria bancrofti from Brugia malayi microfilariae?
37. A traveller from Bihar develops hepatic cysts on ultrasound. Indirect haemagglutination (IHA) titres are 1:512. ELISA is positive for Casoni antigen. Which helminth is most likely responsible, and what is the infective stage for humans?
38. A child in Uttar Pradesh presents with iron deficiency anaemia, hypoalbuminaemia and chronic diarrhoea. Stool examination reveals eggs with a clear space between the embryo and the shell measuring about 60 × 40 µm with a thin transparent shell. Which organism is responsible?
39. Which stage of Leishmania donovani is responsible for transmission to a human host during the bite of a sandfly (Phlebotomus), and in which part of the sandfly gut does it develop?
40. A 32-year-old traveller returning from sub-Saharan Africa presents with daily fever, haemoglobinuria (blackwater fever), and severe haemolytic anaemia. Peripheral blood smear shows ring forms with appliqué (accolé) position and rare but characteristic banana-shaped gametocytes. Which Plasmodium species is responsible?
41. A rapid diagnostic test (RDT) for malaria detects Plasmodium falciparum HRP-2 antigen. A patient from an area with high P. falciparum transmission has a negative microscopy but positive HRP-2 RDT. What is the most likely explanation?
42. A patient with cysticercosis has multiple ring-enhancing lesions on brain MRI. The definitive serological test used for confirmation is:
43. In the diagnosis of visceral leishmaniasis (kala-azar), the rK39 strip test detects antibodies to a recombinant antigen derived from which Leishmania species?
44. A patient returning from a tropical country presents with eosinophilia, urticaria, and passage of large white worms in stool. Stool microscopy shows oval eggs with a mammilated (bumpy) outer coat and fertilised appearance. The drug of choice is:
45. In diagnosing Entamoeba histolytica dysentery, which microscopic finding in a freshly passed stool definitively confirms active amoebiasis (as opposed to non-pathogenic carriage)?
46. A 35-year-old returning traveler from Northeast India presents with fever, hepatosplenomegaly, and pancytopenia. Peripheral smear shows intraerythrocytic parasites with a characteristic 'Maltese cross' (tetrad) appearance. The MOST likely Plasmodium species responsible is:
47. A 10-year-old child from rural Bihar presents with eosinophilia, hepatosplenomegaly, and repeated episodes of fever for 2 years. Serological test (rK39 ELISA) is positive. Bone marrow aspiration shows amastigotes within macrophages. The drug of FIRST CHOICE for treatment in India currently is:
48. A 45-year-old fisherman from coastal Odisha presents with painless subcutaneous nodules over the trunk and extremities, and night blindness. Skin snip microscopy is performed. This test is used for diagnosis of:
49. In the life cycle of Taenia solium, which stage is responsible for neurocysticercosis in humans, and how is it acquired?
50. A 35-year-old farmer presents with right upper quadrant pain and eosinophilia. Ultrasound shows a 7 cm cyst with internal echoes and a 'hydatid sand' sign. Serological testing (ELISA) is positive for Echinococcus. The safest intervention after medical therapy is:
51. Blood film examination of a patient with high-grade fever, thrombocytopenia, and jaundice shows multiple ring forms per erythrocyte, infected cells of normal size, and no visible schizonts. Creatinine is 3.1 mg/dL. Which Plasmodium species and complication are most consistent?
52. Stool microscopy in a child with rectal prolapse shows barrel-shaped eggs with mucous plugs at both poles. The most likely causative organism and its diagnostic characteristic are:
53. A 40-year-old patient from Bihar presents with painless progressive destruction of the nasal septum and palate, and stain of tissue biopsy shows intracellular organisms within macrophages on Giemsa stain (Leishman-Donovan bodies). The drug of choice and its primary mechanism is:
54. A 35-year-old immigrant from Sudan presents with intermittent fever, splenomegaly, and a peripheral blood film showing intraerythrocytic parasites with 'Maurer's clefts' visible inside infected red cells that are not enlarged. Some cells contain multiple ring forms ('appliqué' or accolé forms). The most appropriate next step in confirming the species is:
55. A 30-year-old woman from Rajasthan presents with a hepatic cyst on ultrasound; serology is positive for Echinococcus granulosus by IHA (titre 1:320). Fine needle aspiration is deferred. She is prescribed albendazole. Which laboratory finding in the cyst fluid, if aspirated inadvertently, would be PATHOGNOMONIC for hydatid disease?
56. A 45-year-old returning traveller from Kerala presents with diarrhoea and frothy, foul-smelling pale stools for 3 weeks. Stool microscopy shows pear-shaped trophozoites with two nuclei and a central axostyle — 12–15 µm in length. Which of the following is the BEST confirmatory test for this diagnosis?
57. A 35-year-old man returning from sub-Saharan Africa presents with daily fever spikes, severe anaemia, and haemoglobinuria (blackwater fever). Blood film shows ring forms and banana-shaped gametocytes. Parasitaemia is 12%. Which Plasmodium species and which complication is most likely responsible for the haemoglobinuria?
58. Stool microscopy from a child with rectal prolapse shows oval eggs with a mucus plug at one pole. Adult worms recovered from the colon are 4 cm long, barrel-shaped with three lips. Which helminth is responsible, and which drug is the treatment of choice?
59. A 28-year-old woman presents with seizures. MRI shows multiple ring-enhancing lesions in the brain parenchyma. Serology for cysticercus (EITB) is positive. She recalls eating undercooked pork. What is the infective stage responsible for neurocysticercosis?
60. In the diagnosis of Schistosoma haematobium infection, which specimen and finding is most diagnostic?
61. A 40-year-old man with recurrent urticaria and eosinophilia (1800/µL) is found to have Strongyloides stercoralis on stool examination using the Baermann technique. He is then started on systemic corticosteroids for an unrelated condition. Which serious complication is he most at risk for?
62. A patient from Assam presents with fever, splenomegaly, anaemia and pancytopenia. Bone marrow aspirate shows intracellular amastigotes within macrophages with a distinct kinetoplast (bar-like structure). The drug of choice is:
63. A thick blood smear from a patient with suspected malaria shows rings that occupy more than one-fifth of the RBC diameter, multiple rings per RBC, 'applique' (accolé) forms, and banana-shaped gametocytes. The causative species is:
64. A 32-year-old butcher presents with cystic lesions in the liver found on ultrasound. Serological tests (ELISA, IHA) are positive for Echinococcus. CT scan shows daughter cysts and a 'water lily sign'. The most dangerous complication of percutaneous drainage of this cyst is:
65. A 5-year-old child presents with perianal itching, especially at night. Sellotape swab applied perianally in the morning shows ova that are asymmetric, flattened on one side, and measure approximately 55 × 25 µm. The most appropriate treatment is:
66. A patient with epilepsy from a rural endemic area has multiple small calcified lesions in the brain on CT. Serology shows positive ELISA for cysticercal antibody. Which tapeworm stage is responsible for neurocysticercosis?
67. A 35-year-old male returning from sub-Saharan Africa has daily fever, jaundice, and hemoglobin 7 g/dL. Peripheral blood smear shows parasitized RBCs enlarged to twice normal size, Schüffner's dots, and amoeboid trophozoites. Which Plasmodium species is responsible?
68. A 9-year-old child has a CT scan showing a cyst in the liver with a characteristic 'water lily sign.' Serological testing using indirect hemagglutination is positive at 1:640. The most appropriate initial pharmacological treatment is:
69. Stool microscopy from a patient with bloody dysentery shows trophozoites ingesting erythrocytes. The trophozoites measure 20–40 µm with a finely granular cytoplasm and a single nucleus with central karyosome. Serology for antibodies to Entamoeba is positive. Which test best distinguishes E. histolytica from E. dispar in a reference laboratory?
70. A field-worker in Assam presents with fever, massive splenomegaly, and weight loss over 3 months. Bone marrow aspiration reveals intracellular 2–4 µm oval bodies with a clear halo and a rod-shaped kinetoplast (bar-shaped nucleus) inside macrophages. The treatment of choice for this confirmed diagnosis is:
71. A patient passing pale bulky stools has stool microscopy showing eggs measuring 55–75 × 35–50 µm with a thick shell and an inner polar granule. Peripheral blood shows 30% eosinophilia. Staining with iodine shows the eggs clearly. The causal organism is:
72. A 30-year-old man from Assam presents with prolonged fever, splenomegaly, weight loss, and pancytopenia. Bone marrow biopsy shows Leishman-Donovan bodies in macrophages. Serological test shows positive rK39 ICT. Which treatment is NOW considered first-line in India for visceral leishmaniasis?
73. In a thick blood smear for malaria diagnosis, multiple infected red cells contain a parasite with appliqué (accolé) forms, no enlargement of the RBC, and banana-shaped gametocytes. Which Plasmodium species is present?
74. A child presents with periorbital oedema, myalgia, and eosinophilia after eating undercooked pork. Muscle biopsy shows coiled larvae within a nurse cell. Which organism is responsible and what is the best serological test?
75. A patient passes a segment of tapeworm in stool. Microscopy shows the proglottid has a central uterine stem with 15–20 lateral branches. The patient likely ate undercooked beef. Which species is this and what is the treatment?
76. A 40-year-old rice-farmer from Tamil Nadu presents with haematuria and terminal dysuria. Urine microscopy shows eggs with a terminal spine. The diagnosis is confirmed by detecting circulating cathodic antigen (CCA) in urine. Which trematode and which intermediate host is involved?
77. A patient returning from sub-Saharan Africa presents with fever, anaemia and splenomegaly. Peripheral blood smear shows multiple ring-form trophozoites within a single red cell, some with appliqué (accolé) position, and cytoadherence crescentic gametocytes. Which test would best quantify parasite density and guide severity assessment in this malaria case?
78. A villager in Bihar presents with fever, massive splenomegaly, weight loss and pancytopenia. Splenic aspirate smear stained with Giemsa shows oval bodies with a large nucleus and a kinetoplast (rod-shaped) within macrophages. Which of the following laboratory serological tests has the highest sensitivity for diagnosis of visceral leishmaniasis in endemic settings?
79. Stool examination of a child from rural Assam shows oval eggs measuring 85 × 60 µm with a thick outer layer of mammillated albuminous coat that is bile-stained, containing a segmented embryo. What is the recommended first-line pharmacological treatment?
80. A patient with a known tapeworm (Taenia solium) infection is now found to have multiple ring-enhancing lesions on brain MRI. CSF shows eosinophilia. Serology is positive for Taenia solium antibodies by ELISA. What is the most specific confirmatory test for neurocysticercosis?
81. Schistosoma haematobium infection is differentiated from S. mansoni and S. japonicum clinically and parasitologically by which of the following features?
82. The Knott's concentration technique in parasitology is specifically used to demonstrate:
83. Cerebral malaria (Plasmodium falciparum) is distinguished pathologically by cytoadherence of parasitised RBCs to cerebral endothelium mediated by which parasite ligand?
84. Hydatid disease (cystic echinococcosis) caused by Echinococcus granulosus. The hydatid sand in aspirated cyst fluid consists of:
85. A 30-year-old man presenting with high-grade fever every 72 hours (quartan pattern), splenomegaly, and haemolytic anaemia has a peripheral smear showing infected RBCs of normal or slightly smaller size, band-form trophozoites, and occasional 'rosette' segmented schizonts (6–12 merozoites arranged around a central pigment mass). What is the species and a key clinical concern in this patient?
86. A 12-year-old child from Bihar presents with 3 months of fever, massive splenomegaly, weight loss, and pancytopenia. Bone marrow biopsy shows macrophages laden with oval 2–4 µm intracellular amastigotes (Leishman-Donovan bodies) with a large nucleus and kinetoplast. rK39 rapid antigen test is positive. What is the treatment of choice under the current India National Programme?
87. A patient with epilepsy and ring-enhancing lesions on MRI brain has serum ELISA positive for Taenia solium antibodies. Stool examination shows no Taenia ova. CSF is normal. What is the clinical diagnosis and preferred treatment?
88. A 40-year-old male farmer from Punjab with chronic cough and haemoptysis has sputum microscopy showing golden-brown operculated eggs with a shouldered operculum (22–34 × 12–20 µm). He regularly eats freshwater crabs from local fields. What is the diagnosis?
89. Visceral leishmaniasis (kala-azar) diagnosis in a patient from Bihar with fever, splenomegaly, and progressive wasting. Which combination of tests provides HIGHEST diagnostic sensitivity?
90. In Plasmodium falciparum malaria, the ring forms are seen in peripheral blood smears but mature trophozoites and schizonts are typically absent. The reason is:
91. A patient presents with eosinophilia, urticaria, and a serpiginous skin rash that advances several centimetres per day. Travel history includes walking barefoot on a beach in South India. The causative organism and treatment are:
92. In neurocysticercosis (NCC) caused by Taenia solium, which serological test has the highest specificity for confirmation?
93. A 28-year-old traveller returning from sub-Saharan Africa presents with cyclical fever every 48 hours, severe headache, and altered consciousness. Peripheral blood smear shows small ring forms with multiple rings per RBC, banana-shaped gametocytes, and no stippling. Which plasmodium species is responsible?
94. A 35-year-old man presents with right upper quadrant pain and fever. Ultrasound shows a solitary hypoechoic lesion in the right lobe of the liver. Aspiration yields chocolate-brown ('anchovy sauce') fluid that is odourless. Microscopy of the fluid reveals no trophozoites. Serology for Entamoeba histolytica is strongly positive. The BEST drug of choice for treatment of this amoebic liver abscess is:
95. A 6-year-old child presents with severe anaemia, a pot-belly, and hypoproteinaemia. Stool examination reveals characteristic eggs with a clear plug at each pole ('barrel-shaped eggs with bipolar plugs'). Which parasite is responsible?
96. A 30-year-old woman from Bihar presents with prolonged fever, massive splenomegaly, weight loss, and pancytopaenia. Bone marrow aspirate shows macrophages packed with small oval bodies with a distinct nucleus and kinetoplast. Which organism is this and what is the recommended first-line treatment in India?
97. A 40-year-old man from Kerala presents with episodic painless gross haematuria. Cystoscopy reveals granulomas and sandy patches on the bladder wall. Urine microscopy shows eggs with a terminal spine. Which parasitic infection does this indicate?
98. A 25-year-old butcher presents with a large cyst in the right lobe of the liver identified on ultrasound. CT shows a 'double-wall' cyst with internal daughter cysts. The Casoni skin test is positive. Which parasite is responsible and which is the FIRST intermediate host in its life cycle?
99. In lymphatic filariasis caused by Wuchereria bancrofti, microfilariae exhibit nocturnal periodicity (accumulate in peripheral blood at night). The recommended diagnostic technique and optimal timing for blood sample collection is:
100. The drug of choice for neurocysticercosis (viable parenchymal cysts on MRI with perilesional oedema) in an adult is:
101. A 25-year-old student returning from a trip to Bihar (India) develops fever, weight loss, and massive splenomegaly. Bone marrow aspiration shows numerous amastigotes (Leishman-Donovan bodies) within macrophages. The drug of choice in India for visceral leishmaniasis is: