Used to designate those species of Trypanosoma (genus of protozoa parasitic in the blood and lymph of invertebrates and vertebrates) which occur in the bloodstream of the secondary host, and are transmitted from its mouth when it bites a vertebrate.

Trypanosoma are a genus of Protozoa that causes serious infections in humans and domestic animals. African trypanosomes, of the brucei group, are carried by Tsetse flies and, when they enter the bloodstream of the mammalian host go through a complex series of stages.