CDS (I) 2021 GK Q110: 'Sleeping sickness' is caused

Q: What is the answer to CDS (I) 2021 GK Q110?

A. Correct — A, Trypanosoma. African sleeping sickness is caused by the protozoan Trypanosoma brucei, in two human-infecting subspecies: T. b. gambiense, which produces a slow chronic illness in West and Central Africa and accounts for the great majority of cases, and T. b. rhodesiense, which produces an acute illness in East and Southern Africa. The parasite is passed on by the bite of the tsetse fly, Glossina. The disease runs in two stages — first fever, headache, itching and joint pain as the parasite multiplies in the blood and lymph, then, once it crosses into the central nervous system, confusion, unsteadiness and the wrecked sleep pattern that gives the illness its name. The other three names in the list are all protozoa too, which is what makes the question a genuine test rather than a giveaway.

CDS (I) 2021 General Knowledge · Question 110 of 120

Question text verified against the official CDS question paper.

'Sleeping sickness' is caused by

(a)Trypanosoma
(b)Leishmania
(c)Plasmodium
(d)Paramecium

Answer

Why

Correct — A, Trypanosoma. African sleeping sickness is caused by the protozoan Trypanosoma brucei, in two human-infecting subspecies: T. b. gambiense, which produces a slow chronic illness in West and Central Africa and accounts for the great majority of cases, and T. b. rhodesiense, which produces an acute illness in East and Southern Africa. The parasite is passed on by the bite of the tsetse fly, Glossina. The disease runs in two stages — first fever, headache, itching and joint pain as the parasite multiplies in the blood and lymph, then, once it crosses into the central nervous system, confusion, unsteadiness and the wrecked sleep pattern that gives the illness its name. The other three names in the list are all protozoa too, which is what makes the question a genuine test rather than a giveaway.

Why the others are wrong

(b)Leishmania — Leishmania causes leishmaniasis, whose visceral form is kala-azar. It is spread by the bite of the sandfly, and in India it has long been concentrated in Bihar and neighbouring states.
(c)Plasmodium — Plasmodium causes malaria and is carried by the female Anopheles mosquito. Its fever comes in cycles set by the parasite's release from red cells, which is a quite different clinical picture.
(d)Paramecium — Paramecium is a free-living freshwater ciliate, the slipper-shaped organism of the school pond-water slide. It causes no human disease at all.

Concept

Several major tropical diseases are caused not by bacteria or viruses but by protozoa, and each pairs a parasite with an insect that carries it. Malaria pairs Plasmodium with the female Anopheles mosquito; kala-azar pairs Leishmania with the sandfly; sleeping sickness pairs Trypanosoma with the tsetse fly. Controlling the insect is often as important to controlling the disease as treating the patient.

Read the list as three pathogens and one harmless organism. Paramecium can go at once — it is the pond-water ciliate of the practical class and infects nobody. The remaining three are separated by matching each to its vector, and the tsetse fly is the association to fix for this one. Anchoring to the exam: at the time of the 2021 paper sleeping sickness had already fallen below a thousand reported cases a year, a collapse from the tens of thousands of the 1990s. As of today the trend has held — 675 cases were reported in 2023 and 583 confirmed in 2024 — and the World Health Organization is working towards ending transmission of the gambiense form by 2030.

Key facts

Sleeping sickness is caused by Trypanosoma brucei, in the subspecies gambiense and rhodesiense.
The vector is the tsetse fly of the genus Glossina; the disease is confined to sub-Saharan Africa.
The illness has a first blood-and-lymph stage and a second stage after the parasite reaches the central nervous system.
Fewer than a thousand cases a year have been recorded since 2018; 583 cases were confirmed in 2024.
Leishmania is carried by the sandfly and causes kala-azar; Plasmodium is carried by the female Anopheles and causes malaria.

Study next

Vector-borne diseases and the insect responsible for eachProtozoan diseases: malaria, amoebiasis, kala-azar and sleeping sicknessThe life cycle of Plasmodium and the two hosts it needsKala-azar elimination in India and the sandfly control programmeWorld Health Organization lists of neglected tropical diseases and elimination targets

Common traps

Pairing Leishmania with the tsetse fly; its vector is the sandfly.
Assuming every protozoan in an option list is a pathogen — Paramecium is free-living.
Confusing the mosquito genera: Anopheles for malaria, Culex for filariasis, Aedes for dengue and chikungunya.

As a disease-to-pathogen match, or as a disease-to-vector match with the pathogens supplied as distractors.

Related PYQs

NDA_GAT_2017_I_Q632017Open & attempt →

Sleeping sickness is a parasitic disease of humans and other animals. It is caused by

(a) Histomonas
(b) Trypanosoma
(c) Angomonae
(d) Naegleria

Answer(b) Trypanosoma

The same question with a harder option list. Instead of the familiar protozoa used here, it offers three genuinely obscure names beside Trypanosoma, so the answer has to be recalled rather than reached by eliminating the ones that cause something else.

Practice

practice — not a real PYQ
Kala-azar, the visceral form of leishmaniasis, is transmitted to humans by the bite of
- (a)the tsetse fly
- (b)the sandfly
- (c)the female Anopheles mosquito
- (d)the Aedes mosquito
Answer(b) the sandfly — Leishmania is carried by sandflies, and in India the disease has been concentrated in Bihar and neighbouring states.
practice — not a real PYQ
Which one of the following protozoans is free-living and causes no human disease?
- (a)Entamoeba
- (b)Trypanosoma
- (c)Paramecium
- (d)Plasmodium
Answer(c) Paramecium — the slipper-shaped freshwater ciliate familiar from pond-water slides, which is not a parasite of humans.