Trypanosomiasis

 Trypanosomiasis

Trypanosomiases is a group of protozoal infections of both man and animals caused by trypanosome parasites. The species of trypanosomes consist of T. brucei, T. vivax, T. congolense, T. simiae and T. evansi. Animal trypanosomiasis in Africa represents one of the most serious veterinary problems in the world, and while most other animal diseases have been successfully controlled during this century, trypanosomiasis continues to represent a major threat to animal production in sub-Saharan Africa. The parasites causing the disease are largely transmitted by tsetse flies. Approximately ten million km2 of Africa are infested with tsetse flies and approximately 30 percent of the 150 million cattle in these countries are exposed to the infection. Most infected cattle die if they are not treated. No vaccines are available, however, the disease can be prevented by the use of prophylactic drugs. Another effective control method is to prevent tsetse flies from biting animals.
 
Clinical signs:
Anaemia and general loss of condition are the first clinical signs, when trypanosomes invade and multiply in the bloodstream of the affected animals. About one or two weeks later, the sick animals usually have recurrent fevers for up to three months. There are about twelve days between the bouts of fever. Although after the first bout of fevers, the number of parasites in the circulation declines, the animals continue to be anaemic and lose condition. Some animals can survive many months before dying. A few animals can survive the disease. In the case of T. brucei and T. evansi infections, the parasites can invade brain, eyes and skin and clinical signs like nervous signs, discharges from the eyes, oedematous swellings under the skin can occur.
 
Treatment:
Trypanosomiases can be treated by trypanocidal drugs. In order for the drugs to be effective, early treatment is essential. The drugs can be classified as for therapeutic and prophylactic purposes. The therapeutic drugs for cattle include diminazene aceturate, homidium chloride and homidium bromide. The prophylactic drugs for cattle include homidium chloride, homidium bromide and isometamidium. Because most of these drugs have been in use for many years, many stains of trypanosomes have developed drug resistance towards these drugs. In order to try to overcome this difficulty, some countries have policies in restricting the use of drugs. Some drugs are reserved in the case of that drug resistance develops towards the drugs in use.
 
Control measures:
Trypanosomiasis can be prevented by the use of prophylactic drugs. The prophylactic drugs currently used for cattle are homidium and isometamidium. After properly injecting into the animals, these drugs can usually provide three months protection. Prophylactic drugs are very effective to be used to protect animals at times when they are exposed to constant disease challenge. Unfortunately, because these drugs have been in use for many years and in many places they were not properly used, resistance has been developed in some places. Another effective control method is to eradicate the vectors, tsetse flies, which transmit the disease. Various strategies have been used to control tsetse flies. These include spraying insecticide on tsetse habitat, destruction of tsetse habitat and alteration of vegetation so that it becomes not suitable for tsetse flies. It appears that trypanosomiasis can be eliminated, at least from much of Africa, by eradicating tsetse flies. However, this method is very costly and requires a high level of management, organisation and specialist expertise.