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. 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. In order for the transfer of the disease from the flies to the animals, interruption of feeding habits needs to occur. This direct transmission technique involves them cutting the skin with their mouths, then lapping up the blood along with connective tissue fluid. This means a good indicator of disease would be looking at trypanosome density in capillary blood and connective tissue. After transferring the infectious organisms to the host species, the flies leave to rest and during that time transmission was successful only in some cases. Because the trypanosomes remain in the food canal of the flies for 4–8 hours depending on the species, the flies can feed off of one animal's blood more than one time, thus increasing the chance of successful transmission. Although the most common method of transferring trypanosomes to other species is through tabanus flies, there are other insects that can also transmit this disease to livestock. These blood sucking insects are Stomoxys, Haematobia (also known as Lyperosia), Haematopota, and Ornithordorus. Other methods of transmission still being studied are looking at passing T.evansi thorough iatrogenic transmission. Evidence has been seen of transmission through eating infected meat and also through vampire bats in geographical areas where they are found.