Surra is a disease of animals caused by a tiny parasite called Trypanosoma evansi. It affects animals mainly in tropical and subtropical regions.
Unlike the parasite associated with African tsetse-transmitted trypanosomiasis, Trypanosoma evansi does not need tsetse flies to spread. Instead, it is carried from animal to animal by biting flies such as horse flies and other flies that feed on blood. Because these flies are found in many parts of the world—not just where tsetse flies live—surra has been able to spread widely. The disease occurs in North Africa, the Middle East, Asia, the Far East, and Central and South America.
A wide variety of animals can become infected with surra. In some species, especially horses, camels, and dogs, the disease can occasionally cause severe illness or death. Cats usually have mild disease, but infected cats can help spread the parasite to other species. Many other mammals can be infected and might develop long-term illness that lasts months or even years. Some animals show no clear symptoms but still carry the parasite.
Surra is not considered a major human health risk and is very rarely reported in people. Surra causes important economic losses, especially in areas that depend on working animals and livestock.
