This species occurs in South America, where it causes a disease known as mal de Caderas in horses. The disease is similar to surra. T. equinum differs morphologically from T. evansi only in lacking a kinetoplast. However, strains of T. evansi without a kinetoplast have appeared in the laboratory, and T. equinum undoubtedly originated in this way.
T. equinum is transmitted mechanically by tabanids. Both antrycide methyl sulfate and suramin can be used in treating it. The former is less toxic. A single subcutaneous dose of 5 mg/kg or less of antrycide methyl sulfate or a single intravenous dose of 4 g per 1000 lb body weight of suramin can be used. Control measures are the same as for T. evansi.
This species, which was once thought to be the same as T. simiae, was rediscovered in the Belgian Congo by Peel and Chardome (1954). It is a member of the brucei group, but differs from the others in being monomorphic, having only stout forms 14 to 19 u long, with a short, free flagellum. The kinetoplast is very small and marginal.
T. suis occurs in pigs, causing a chronic infection in adults and a more acute disease with death in less than 2 months in young pigs. Peel and Chardome attempted without success to transmit T. suis to the goat, sheep, dog, white rat, guinea pig, Cricetomys gambianus, Dendrohyrax, chimpanzee, cat, rabbit, cattle, monkey and ass. It is transmitted by the tsetse fly, Glossina brevipalpis, in which it develops first in the intestine and proventriculus and then in the salivary glands. Metacyclic infectious trypanosomes appear in the hypopharynx on the 28th day.