African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals. The disease occurs regularly in some regions of sub-Saharan Africa with the population at risk being about 70 million in 36 countries.

It is usually transmitted by the bite of an infected tsetse fly and is most common in rural areas.The tsetse fly (genus Glossina) is a large, brown, biting fly that serves as both a host and vector for the trypanosome parasites. While taking blood from a mammalian host, an infected tsetse fly injects metacyclic trypomastigotes into skin tissue. From the bite, parasites first enter the lymphatic system and then pass into the bloodstream.

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