Any of a set of debilitating long-term
diseases caused by a trypanosome (protozoan
of the genus Trypanosoma). They include
sleeping sickness (nagana) in Africa,
transmitted by the bites of tsetse flies, and
Chagas' disease in the Americas, spread by
assassin bugs. Trypanosomes can live in the
bloodstream of humans and other vertebrates.
Millions of people are affected in warmer
regions of the world; the diseases also
affect cattle, horses, and wild animals,
which form a reservoir of infection.