A tropical disease caused by Trypanosoma is

Step 1: Analyze the question The question asks which tropical disease is caused by Trypanosoma, a genus of parasitic protozoa.

Step 2: Explain the concept Different tropical diseases are caused by different kinds of organisms:

| Disease | Causative agent | Vector | |---|---|---| | Sleeping sickness (African trypanosomiasis) | Trypanosoma brucei gambiense / rhodesiense (protozoan) | Tsetse fly (Glossina) | | River blindness (onchocerciasis) | Onchocerca volvulus (nematode worm) | Blackfly (Simulium) | | Yellow fever | Flavivirus (virus) | Aedes mosquito | | Malaria | Plasmodium (protozoan) | Female Anopheles mosquito |

Step 3: Work through the options

• A. Sleeping sickness: Correct. Trypanosoma lives in the blood and, later, the nervous system, causing fever, drowsiness and eventually death if untreated. It is spread by the tsetse fly.
• B. River blindness: Wrong. It is caused by a worm, Onchocerca volvulus.
• C. Yellow fever: Wrong. It is caused by a virus.
• D. Malaria: Wrong. It is caused by Plasmodium, which is also a protozoan, so be careful not to confuse the two.

Step 4: Answer The correct option is A, sleeping sickness.

Exam tip: Link each disease to its organism and vector:

• Trypanosoma → Tsetse fly → Sleeping sickness ("T-T-S")
• Plasmodium → Anopheles → Malaria
• Onchocerca → Blackfly → River blindness