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
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.
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.
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.
WWW Sites of Relevance
University of Missouri - Social Sciences Unit
Programme against African Trypanosomiasis (PAAT)
Integrated Control of Ticks and Tick-Borne Diseases