Trypanosoma

Genus of Protozoa that causes serious infections in humans and domestic animals. African trypanosomes, of the brucei group, are carried by Tsetse flies ( Glossina ) and, when they enter the bloodstream of the mammalian host go through a complex series of stages. Perhaps the most interesting feature is that there are recurrent bouts of parasitaemia as the parasite alters its surface antigens to evade the immune response of the host (see antigenic variation). The repertoire of antigenic variation is considerable. The S. American trypanosomes (of which T. cruzi is the best known) are carried by reduviid bugs, and cause a chronic and incurable disease (Chagas disease). Other interesting features of trypanosomes are the kinetoplast DNA and glycosomes (organelles containing enzymes of the glycolytic chain).