Parasitology Questions and Answers

Answer: D

The correct match is P-(iii), Q-(i), R-(iv), S-(ii).

• Ascaris lumbricoides, the large roundworm, lives as an adult in the small intestine (iii).
• Dracunculus medinensis, the guinea worm, lives in subcutaneous tissue; the female emerges through a blister, usually on the leg (i).
• Enterobius vermicularis, the pinworm, lives in the caecum and appendix and migrates to the perianal skin to lay eggs (iv).
• Wuchereria bancrofti adults live in the lymphatic vessels and lymph nodes, causing lymphatic filariasis and elephantiasis (ii).

Options A, B and C each put the guinea worm or the filarial worm in the wrong tissue.

Answer: D

The correct match is P-2 ; Q-1 ; R-4 ; S-3.

• African sleeping sickness is caused by Trypanosoma brucei, spread by the tsetse fly.
• Chagas disease, in the Americas, is caused by Trypanosoma cruzi, spread by triatomine (kissing) bugs.
• Elephantiasis (lymphatic filariasis) is caused by the nematode Wuchereria bancrofti, spread by mosquitoes.
• Lyme disease is caused by the spirochaete Borrelia burgdorferi, spread by ticks.

Rickettsia rickettsii causes Rocky Mountain spotted fever and matches none of the four. The option with P-2 but Q-4 and R-1 swaps the filarial worm and T. cruzi, and the others misplace the trypanosomes.

Answer: B

Toxoplasma gondii is a parasite; it is the only term the key accepts in this multiple-select question.

T. gondii is a protozoan of the phylum Apicomplexa, related to the malaria parasite. It is an obligate intracellular parasite: it can multiply only inside host cells. Cats are its definitive hosts, where sexual reproduction takes place, while humans and many other warm-blooded animals act as intermediate hosts, infected through oocysts or tissue cysts in undercooked meat.

It is a eukaryotic cell with a nucleus and organelles, so it is not a virus or a bacterium, and it is a protozoan rather than a fungus.

Answer: B

Exo-erythrocytic schizogony occurs in the Liver.

The sporozoites injected by the mosquito travel in the blood to the liver and enter hepatocytes. There they multiply asexually by schizogony, outside red cells (hence exo-erythrocytic), and release thousands of merozoites.

Only those merozoites then invade red blood cells and begin erythrocytic schizogony, which causes the fever. 'Blood' is too vague and is where the merozoites travel, and in the mosquito the stage is sporogony, with oocysts on the stomach wall, not schizogony.

Answer: D

Both are transmitted by Mosquitoes.

Yellow fever virus is spread mainly by Aedes mosquitoes, especially Aedes aegypti, and West Nile virus mainly by Culex mosquitoes, with birds as its main reservoir.

Ticks transmit diseases such as Lyme disease and Kyasanur Forest disease, kissing bugs (triatomines) transmit Chagas disease, and deer flies transmit tularaemia and loiasis. None of them is the vector of these two fevers.

Answer: A

The true combination is sand fly and Leishmania.

Kala-azar, visceral leishmaniasis, is caused by the protozoan Leishmania donovani. It is transmitted by the bite of the female sand fly, Phlebotomus argentipes in India. The parasite multiplies in macrophages of the spleen, liver and bone marrow, causing fever, an enlarged spleen and greyish skin, the 'black fever' of the name.

The tsetse fly (Glossina) and Trypanosoma cause African sleeping sickness. Mosquitoes and Plasmodium cause malaria, and mosquitoes and microfilarial worms cause lymphatic filariasis.