THE TSETSE FLY
The tsetse fly and
the trypanosome parasite it carries have kept from tropical Africa the
agro-economic revolution that occurred in the Middle East
around 4,000 B.C.
— John Brady, ‘Seeing Flies from Space’, Nature, Vol. 351, 1991
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O CONTINENT remains dominated by one livestock disease to the extent
that Africa is by trypanosomosis,
known as sleeping sickness when it occurs in people. The parasite that causes
this disease is transmitted to people and animals by the tsetse fly
(pronounced tet´see). Found only in Africa, these
flies occur in 38 countries south of the Sahara Desert,
22 of which are among the most underdeveloped in the world.
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The presence of the testse fly and the disease it
causes over an area the size of the continental USA largely accounts for
Africa’s ruminant livestock productivity being only one-seventieth that of
Europe and America. Thirty per cent of Africa’s
160 million cattle population and comparable numbers of small ruminants are at
risk from this disease. This fly also jeopardises the lives of 55 million
people. Every year some 250,000 to 300,000 men, women and children are left to
suffer and die because their illness goes undiagnosed and untreated. And every
untreated, undiagnosed infected human and animal creates a new host for each
uninfected tsetse fly. Because livestock infected with trypanosome parasites
are a source of further tsetse infection, better control of the disease in
livestock would help improve control of the human disease. The World Health
Organization estimates we are now in the midst of one of the largest epidemics
of sleeping sickness in this century.
Dr. Michaleen Richerof the
International Medical Corps has said the prevalence of sleeping sickness has risen by more than 15 percent. ‘This is an epidemic of
really catastrophic proportions,’ Richer added. The IMC, U.S. Centers for
Disease Control and Prevention, CARE and other organizations are in the midst
of a major effort, which began in 1997, to identify people infected with
sleeping sickness and contain the epidemic. But the organisations say their efforts
could take years.
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HERE ARE altogether 23 species of tsetse flies. Some live in tropical rain
forests, some in the riverine gallery forests and
others in the savannah woodlands of Africa.
The tsetse fly is one of very few insects that bears fully grown larvae (one
every nine days) rather than laying eggs. Both sexes feed exclusively on
the blood of verte-brate animals,
including cattle, sheep, goats, pigs and horses. And both sexes transmit
deadly disease.
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Milk, not meat, is a main food in Africa. The
untimely death of a milking cow on a small farm has large and sometimes tragic
consequences because the milk provided by a single cow meets the basic
nutritional needs of many households. Keeping a cow also allows very poor
farmers to enter the cach economy with sales of
surplus milk. The small regular cash income pays for grain, farm inputs,
medicines and school fees.
For millions of people in Africa—including small-scale farmers who depend
heavily on their cattle, sheep and goats to feed and care for their
families—prospects for better human and animal health will very much depend on
whether or not scientific research can find ways to control the tsetse fly and
its deadly parasitic cargo.
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Scanning
electron micrograph of a trypanosome, the parasite that causes trypanosomosis, a wasting disease that afflicts people
and their livestock.
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INTERNATIONAL LIVESTOCK RESEARCH INSTITUTE
______________________________________________________________________________________________________________
Conducting research in animal agriculture to
reduce hunger, poverty and environmental degradation in developing countries.
Box
30709, Nairobi, Kenya Phone
+ (254-2) 422-3000 Fax + (254-20) 422-3001 E-mail
ILRI-Kenya@cgiar.org Web www.ilri.org
