Parasitology: helminths

45 Kerala PSC Lab Technician Gr II practice questions on Parasitology: helminths, 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.

1. Question 1 · Easy

   Which mosquito is the main vector of Wuchereria bancrofti in India?

   1. ACulex quinquefasciatus
   2. BMansonia annulifera
   3. CAedes aegypti
   4. DAnopheles stephensi

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   Answer: A · Culex quinquefasciatus

   Bancroftian filariasis, the commonest form in India, is transmitted mainly by Culex quinquefasciatus, which breeds in dirty, stagnant water in towns. Brugia malayi, found in parts of Kerala, is transmitted by Mansonia mosquitoes that breed in ponds with water plants such as Pistia. Microfilariae taken up by the mosquito develop into infective larvae in about two weeks. Vector control and mass drug administration are the basis of the elimination programme.

   • B: Mansonia transmits Brugia malayi, mainly in Kerala.
   • C: Aedes aegypti transmits dengue, chikungunya and Zika.
   • D: Anopheles stephensi is an urban vector of malaria.

2. Question 2 · Medium

   After Ascaris lumbricoides eggs are swallowed, the hatched larvae:

   1. AMigrate to the perianal skin
   2. BEncyst in skeletal muscle
   3. CMature directly in the small intestine
   4. DPass through the lungs before maturing in the gut

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   Answer: D · Pass through the lungs before maturing in the gut

   Larvae hatch in the small intestine, penetrate the wall and reach the liver and lungs through the blood. In the lungs they moult, break into the alveoli, climb up the trachea and are swallowed, maturing into adults in the small intestine about 2 months after infection. The lung stage can cause cough, fever and eosinophilic infiltrates (Loeffler syndrome). Eggs appear in stool only after the adults mature.

   • A: Female Enterobius worms migrate to the perianal skin.
   • B: Encysting in muscle is typical of Trichinella spiralis.
   • C: Enterobius and Trichuris mature in the gut without a lung stage.

3. Question 3 · Easy

   In which animal do adult Echinococcus granulosus worms live?

   1. AHumans
   2. BSheep
   3. CDogs
   4. DCattle

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   Answer: C · Dogs

   The adult tapeworm, only a few millimetres long, lives in the small intestine of dogs and other canines, which pass eggs in their feces. Sheep, cattle and humans are intermediate hosts, in which the larva grows as a hydatid cyst, mainly in the liver and lungs. Humans are infected by swallowing eggs from dog feces, through close contact with dogs or contaminated food. Humans are a dead-end host, as their cysts are not eaten by dogs.

   • A: Humans are accidental intermediate hosts and develop cysts, not adult worms.
   • B: Sheep are intermediate hosts that carry hydatid cysts.
   • D: Cattle are intermediate hosts, like sheep.

4. Question 4 · Easy

   How do humans mainly acquire hookworm infection?

   1. ASwallowing embryonated eggs in food
   2. BFilariform larvae penetrating the skin
   3. CThe bite of an infected mosquito
   4. DEating undercooked pork or beef

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   Answer: B · Filariform larvae penetrating the skin

   Hookworm eggs passed in feces hatch in warm, moist soil into rhabditiform larvae, which moult into infective filariform (third-stage) larvae. These penetrate the skin, usually of bare feet, and travel through the blood and lungs to the small intestine. Wearing footwear and proper sanitation prevent infection. Ancylostoma duodenale can also be acquired by swallowing larvae, but skin penetration is the main route.

   • A: Swallowing embryonated eggs is how Ascaris and Enterobius are acquired.
   • C: Mosquito bites transmit filarial worms and malaria, not hookworm.
   • D: Undercooked pork or beef transmits Taenia tapeworms.

5. Question 5 · Medium

   Fluid aspirated from a liver cyst of a 38-year-old shepherd contains a fine granular deposit called hydatid sand. It consists of:

   1. AProtoscolices and brood capsules
   2. BFragments of dead adult worms
   3. CCalcified eggs of the tapeworm
   4. DCrystals of cholesterol and calcium

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   Answer: A · Protoscolices and brood capsules

   The inner germinal layer of a hydatid cyst buds off brood capsules, each containing several protoscolices. Brood capsules and protoscolices that break free settle in the cyst fluid as a fine granular deposit called hydatid sand. Microscopy of the fluid shows protoscolices with rows of hooklets, or loose hooklets. Spilled cyst fluid can cause anaphylaxis and seed new cysts, so aspiration is done with care.

   • B: No adult worms develop in the intermediate host.
   • C: Eggs are formed only by the adult worm in the dog intestine.
   • D: Crystals are not the deposit called hydatid sand.

6. Question 6 · Easy

   The egg of Enterobius vermicularis is typically:

   1. APlanoconvex, flattened on one side
   2. BOval with a prominent lateral spine
   3. CRound with a radially striated shell
   4. DBarrel-shaped with a plug at each pole

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7. Question 7 · Hard

   A 30-year-old man from Kollam has had a dry night cough and wheeze for 2 months. Absolute eosinophil count is 6,500/µL (reference under 450/µL), serum IgE is very high and filarial antibody is strongly positive, but night blood films show no microfilariae. The most likely diagnosis is:

   1. AChronic filarial lymphedema
   2. BLoeffler syndrome from Ascaris
   3. CTropical pulmonary eosinophilia
   4. DStrongyloides hyperinfection

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8. Question 8 · Hard

   In Stoll's dilution method, 4 g of formed stool from an anemic 12-year-old is made up to 60 mL with N/10 sodium hydroxide. The hookworm eggs in 0.15 mL of the suspension number 30. What is the egg count per gram of stool?

   1. A12,000
   2. B200
   3. C750
   4. D3,000

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9. Question 9 · Medium

   How do humans develop cysticercosis?

   1. ABy the bite of an infected fly
   2. BBy eating undercooked measly pork
   3. CBy swallowing eggs of Taenia solium
   4. DBy eating undercooked infected beef

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10. Question 10 · Medium

    A 35-year-old plantation worker in Idukki has hemoglobin 7 g/dL (reference 13-17 g/dL) and hookworm eggs in his stool. His blood film is most likely to show:

    1. AMacrocytic red cells and oval forms
    2. BMicrocytic hypochromic red cells
    3. CNormocytic normochromic red cells
    4. DSpherocytes with polychromasia

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11. Question 11 · Hard

    Unpreserved stool from an anaemic 9-year-old in Wayanad reaches the laboratory two days after collection. The saline mount shows rhabditiform larvae with a long buccal canal and a small genital primordium, but no eggs. The most likely explanation is:

    1. AEnterobius larvae from the perianal skin
    2. BFree-living soil nematode contamination
    3. CHookworm larvae hatched from eggs on standing
    4. DStrongyloides stercoralis infection

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12. Question 12 · Easy

    Which helminth lays a barrel-shaped, bile-stained egg with a clear plug at each pole?

    1. AAscaris lumbricoides
    2. BTrichuris trichiura
    3. CAncylostoma duodenale
    4. DEnterobius vermicularis

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13. Question 13 · Hard

    A 62-year-old man on long-term prednisolone for COPD develops cough, diarrhoea and E. coli septicaemia. A wet mount of his sputum shows actively motile, slender larvae with a long oesophagus and a notched tail. The most likely diagnosis is:

    1. ATropical pulmonary eosinophilia
    2. BHookworm larval migration
    3. CAscaris larval pneumonitis
    4. DStrongyloides hyperinfection

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14. Question 14 · Easy

    What is the infective stage of Ascaris lumbricoides for humans?

    1. AFilariform larva
    2. BUnembryonated egg
    3. CEmbryonated egg
    4. DRhabditiform larva

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15. Question 15 · Medium

    Hymenolepis nana differs from most tapeworms because:

    1. AIts adult worm lives in the liver
    2. BHumans are only its intermediate host
    3. CIt has operculated eggs
    4. DIt can complete its cycle in one host

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16. Question 16 · Medium

    Diagnostic needle aspiration of a suspected hydatid cyst is usually avoided because leaking cyst fluid may cause:

    1. ARapid calcification of the cyst
    2. BAnaphylaxis and new daughter cysts
    3. CMassive bleeding from the cyst
    4. DCysticercosis in the patient

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17. Question 17 · Easy

    Which mosquito genus mainly transmits Brugia malayi in the coastal belt of Kerala?

    1. AMansonia
    2. BCulex
    3. CAedes
    4. DAnopheles

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18. Question 18 · Medium

    A gravid proglottid passed in stool is pressed between slides and shows 9 lateral uterine branches on each side. This identifies:

    1. ATaenia solium
    2. BEchinococcus granulosus
    3. CDipylidium caninum
    4. DTaenia saginata

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19. Question 19 · Medium

    An adult hookworm recovered after treatment has two pairs of curved teeth in its buccal capsule. It is:

    1. AStrongyloides stercoralis
    2. BNecator americanus
    3. CAncylostoma duodenale
    4. DTrichuris trichiura

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20. Question 20 · Easy

    Eating undercooked meat of which animal transmits Taenia saginata to humans?

    1. ACattle
    2. BPig
    3. CFish
    4. DCrab

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21. Question 21 · Easy

    Which intestinal nematode is usually diagnosed by finding larvae, not eggs, in fresh stool?

    1. AAscaris lumbricoides
    2. BStrongyloides stercoralis
    3. CEnterobius vermicularis
    4. DTrichuris trichiura

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22. Question 22 · Medium

    Why may unfertilized Ascaris eggs be missed by saturated salt flotation?

    1. AThey are heavy and do not float
    2. BThey are destroyed by the salt
    3. CThey lose their outer coat
    4. DThey stick to the container wall

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23. Question 23 · Medium

    A man with chronic bancroftian filariasis passes milky urine that clears on shaking with ether. This finding indicates:

    1. AHaemoglobinuria
    2. BPyuria
    3. CPhosphaturia
    4. DChyluria

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24. Question 24 · Hard

    A 34-year-old man returns to Kerala after two years of farm work in Nigeria. He has painful passage of blood at the end of urination. A midday urine deposit shows large eggs with a terminal spine. The infection is most likely:

    1. ASchistosoma mansoni
    2. BSchistosoma japonicum
    3. CWuchereria bancrofti
    4. DSchistosoma haematobium

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25. Question 25 · Easy

    A colourless, thin-shelled oval egg with a segmented ovum of 4-8 cells and a clear space under the shell is typical of:

    1. ATaenia species
    2. BAscaris lumbricoides
    3. CHookworm
    4. DTrichuris trichiura

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