Correct Option: D

Human African trypanosomiasis, sleeping sickness, African lethargy, or Congo trypanosomiasis is a parasitic disease of people and animals, caused by protozoa of the species Trypanosoma brucei and transmitted by the tsetse fly. It results in swelling of the brain. The disease is endemic in some regions of sub-Saharan Africa, covering areas in about 37 countries containing more than 60 million people. An estimated 50,000 to 70,000 people are currently infected, the number having declined somewhat in recent years. The tsetse fly is a large, brown, biting fly that serves as both a host and vector for the trypanosome parasites.