Surra

Surra (from the Marathi sūra, meaning the sound of heavy breathing through nostrils, of imitative origin) is a disease of vertebrate animals. The disease is caused by protozoan trypanosomes, specifically Trypanosoma evansi, of several species which infect the blood of the vertebrate host, causing fever, weakness, and lethargy which lead to weight loss and anemia. In some animals the disease is fatal unless treated.

An acute form of the disease, which is generally fatal unless treated, occurs in horses, donkeys, mules, cattle, buffalo, deer, camels, llamas, dogs, and cats. This form is caused by Trypanosoma evansi (Steel 1885) (Balbiani 1888), and is transmitted by horse-flies, and also by the vampire bat, Desmodus rotundus, in South-America. This form occurs in South America, Northern Africa, and the Middle East. This was the first form of pathogenic trypanosome discovered and was first described by Griffith Evans in 1880 while he was working in India.

A chronic form of the disease, which is milder but persistent, occurs in pigs, sheep, and goats. This form is caused by Trypanosoma suis and is transmitted by tsetse. This form occurs in Africa.

Surra is also known from other countries; an unspecified form is locally common in Mindanao, in the Philippines.

Trypanosoma evansi, although monomorphic in most cases, can be pleomorphic in some strains. They are characterized by a long free flagellum with a narrow drawn out posterior. Kinetoplast and dyskinetoplastic forms appear. Kinetoplast is either terminal or subterminal.

Transferred by species of Tabanus flies, Trypanosoma evansi development does not take place in the actual vector. In order for the transmission to be successful, trypanosomes need to survive in the gut of the flies and be regurgitated during subsequent feeding. Since tabanidae are most abundant during rainy and post rainy seasons, that is when most outbreaks of Surra occur.

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