TRYPANOSOMA, a genus of flagellate Protozoa included in the order Binucleata which are characteristic parasites of vertebrates and insects. Related genera live in the gut of in sects but Trypanosoma is parasitic in the blood of vertebrates (except Tr. equiperdum). The species are transmitted by blood-sucking sects, especially the biting flies (Glossina), and it is probable that a sexual generation is developed in the insect in alternation with the asexual generation in the vertebrate host.
The species are difficult to characterize and thus far are distinguished only by culture ex periments. The number of known forms and of diseases produced by them is rapidly in creasing. Among the most important are the following: Trypanosoma lewisi from the rat, transmitted by fleas and lice, cosmopolitan, probably not pathogenic. Tr. brucei in cattle, horses, mules and wild herbivores, transmitted by Glossina, produces nagaila or tse-tse fly disease. It occurs in Africa south of the
Sahara. Tr. equiperdum, in horse and ass, transmitted by contact (and by biting flies?) produces dourine. It is endemic in the circum Mediterranean area and has been introduced into nearly all regions, including North ica. Tr. evansi, in domestic and wild mammal's, transmitted by Stomoxys and Tabanus, pro duces surra in India, China and the Philip pines. Tr. equinum, in horses, causes mal de caderas in South America. Tr. gambiense, in man, transmitted by Glossina, produces sleep ing. sickness. It occurs in equatorial Africa (elsewhere by importation).
The most of the diseases named are very severe and recovery is rare so that these sites rightly rank as the most dangerous known.