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Discovery of the Tsetse Fly Genome Makes African Farmers Hopeful

25 April 2014

FAO

AFRICA - Scientists have cracked the genetic code of the tsetse fly hematophagous, giving hope that the discovery will help in future efforts to combat one of the diseases most devastating to livestock in sub-Saharan Africa.


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© Geoffrey M. Attardo, Researcher, Yale School of Public Health

The bite of a tsetse carrier of the parasite can cause animal trypanosomiasis and sleeping sickness in humans
genome of the tsetse fly has been sequenced and annotated by an international collective effort of ten years in which participated the Laboratory of Insect Pests Control, managed jointly by the United Nations Food and Agriculture Organization (FAO) and the International Atomic Energy Agency (IAEA) in Vienna.

This discovery allows scientists to better study the fly genes and their functions. This knowledge should open the door to research ways to combat the insect. Tsetse flies, which are found only in Africa-are vectors of parasitic protozoa causing trypanosomiasis or nagana. This can often result in a fatal disease that affects about three million animals in the region every year, at enormous cost to the livelihoods and food security of farmers.

The disease causes a state of chronic weakness in cattle fertility and reduces the production of meat and milk, prevents weight gain and makes animals too weak to be used for plowing and transport, which in turn affects agricultural production.

The sting of the tsetse in humans can cause sleeping sickness, which can be fatal without proper treatment. There exists no vaccine against the disease for livestock or humans because the parasite is able to avoid the immune systems of mammals. Control methods are mainly tsetse traps, pesticide treatments and strategies to release sterile males.

"Decoding the DNA of the tsetse fly is a major scientific breakthrough that paves the way for a control most effective of trypanosomiasis, which is good news for millions of farmers and livestock keepers in sub-Saharan Africa," said Kostas Bourtzis the Joint FAO / IAEA Division of Nuclear Techniques in Food and Agriculture Division. "Detection and trypanosomiasis are an expensive day complex and harmful to the cattle, as they often involve the use of toxic drugs, but this new knowledge will accelerate research on the methods of controlling tsetse and help scientists to develop new and complementary ways to reduce the use of expensive drugs and insecticides strategies."

He said unique features in decoding of the genome focused on the relationship of tsetse with symbiotic bacteria, Wolbachia, which in many species of insects affects the biology and physiology of its host, including reproduction, mating behavior and ability as a vector.

"Our group has been involved in the discovery horizontal transfer of large sections of the genome sequence of the bacterium Wolbachia in tsetse genome, "said Bourtzis. "We are currently investigating, how these gene insertions affect the biology of the tsetse."

The complex relationship tsetse with Wolbachia and two other symbiotic bacteria are part of their unique biology, which also consists of feeding exclusively on vertebrate blood, giving birth to live larvae, which feeds by a milk duct.

A first set of conclusions on the genome of the tsetse fly will be published in the journal Science in an article entitled "Genome sequence Tsetse (Glossina morsitans) vector of African trypanosomiasis."

Sterile insect technique Division Joint FAO / IAEA currently supports 14 African countries in their efforts to address the problem of trypanosomiasis by controlling populations of tsetse through integrating the sterile insect technique with other methods to combat it.

Used in birth control of insects, the sterile insect technique involves the release of male-reared flies in large numbers and have been sterilized with low dose radiation-infested areas, where they mate with wild females. These do not produce offspring and as a result, the technique can be eliminated and, if applied systematically over an area extensively to ultimately eradicate populations of wild flies.

Tsetse flies were successfully eradicated from the island of Zanzibar, using the sterile insect technique and currently are being lifted in parts of southern Ethiopia. In January, Senegal reported that it was making significant progress in infested areas in the region Niayes with the same method.

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