Surra is typanosomal disease of horses, caused by infection with the prozotoal parasite, Trypanosoma evansi. The disease is characterized by weight loss, anemia, recurrent fever and eventual death in affected horses living in Asia, Africa, and South America. Although horses are the most severely affected, several other species of animals can become infected, including livestock species (pigs, cattle, goats, sheep, llamas), domestic pets (dogs, cats), and wildlife (buffalo, camels, elephants). Large outbreaks can occur among horses in areas with high populations of vector and reservoir horses.

Transmission
Surra is transmitted by biting flies and vampire bats. Capybaras (a large rodent) and coatis (part of the raccoon family) are thought to act as reservoirs of the organism. Horses can sometimes develop surra as an inapparent infection, where they are capable of transmitting the disease to vectors. Trypanosomas reproduce in the blood of the vertebrate host, and the trypomastigote forms are transmitted mechanically by bloodsucking insects between animals.

Incubation period
The incubation period is 1 to 2 weeks.