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After a four-year eradication programme that included nuclear techniques, the Niayes region of Senegal is now virtually free of the tsetse flies that once decimated livestock. The tsetse fly is a blood-sucking insect that kills more than 3 million head of livestock each year in sub-Saharan Africa, costing more than $4 billion annually. It transmits a parasite that causes a wasting disease in cattle called Nagana. In certain parts of Africa, the tsetse fly has also been responsible for more than 75,000 cases of “sleeping sickness” in humans, a disease that affects the central nervous system and causes disorientation, personality changes, slurred speech, seizures, difficulty walking and talking, and ultimately death. The Senegalese government has implemented a multi-year programme to gradually eliminate the tsetse fly using a method called the sterile insect technique, with financial assistance from the United States and technical support from France’s International Centre for Agricultural Development (CIRAD). The programme is supported by a joint unit of FAO and the International Atomic Energy Agency (IAEA) in Vienna.
Four years ago, a campaign was launched in the Niayes region, close to the capital Dakar, to control the tsetse fly, a pest that spreads a disease that devastates livestock, paving the way for its complete eradication.
“I haven’t seen a single tsetse fly in a year,” said cattle farmer Omar Sow. “This is in stark contrast to before, when their numbers increased, especially during the cold season. These flies were a real nuisance for our livestock and we had to choose our milking times carefully. Now, this is no longer a problem.”
Eradicate reproduction
Senegal has successfully integrated an insect fertility control technology that uses radiation to sterilize male flies, thereby gradually reducing fly populations. Baba Sall, project manager at Senegal’s Ministry of Livestock and Animal Production, said the technology has eliminated fly populations in one area of the Niayes region and suppressed fly populations by 98% in another area, and will be implemented in a third area in 2016.
“Eradication of flies will significantly improve food security and contribute to socio-economic progress,” Sall said, adding that a study of 227 farms showed that the income of the rural population in Niayes would increase by 30 percent.
“Not only has life become more comfortable for the animals, but also for the farmers,” said Loulou Mendy, a pig farmer in the area. “Now we can even sleep in the open air. Before, this was unthinkable because of the tsetse fly bites.”
Senegal is one of 38 African countries infested with tsetse flies, covering a total area of about 60,000 square kilometres. Tsetse control operations were launched in 2011 in the Niayes region near the capital Dakar.
The Senegalese government chose the area because it is particularly suitable for raising cattle that produce more milk and meat than other areas. However, due to the nagana disease, there is a high incidence of livestock infertility and weight loss, resulting in reduced meat and milk production, and the cattle are too weak to plough the land or transport agricultural products, which in turn seriously affects crop production, said Mark Fresen, Director of the Insect Pest Control Laboratory of the Joint FAO/IAEA Department of Nuclear Techniques in Food and Agriculture.
Nuclear sterilization shows positive results
Vreysen explains that sterilization using nuclear techniques is most effective when conventional techniques have significantly reduced fly populations, but small numbers of insects remain. “The sterilized male flies will search for unmated females,” he says. “This will lead to the complete extinction of fly populations in those areas.”
The project in Senegal began with a feasibility study launched in 2006, supported by the IAEA, FAO, the Centre for International Cooperation in Agricultural Research for Development (CIRAD) and the Government of Senegal, through the Senegalese Agricultural Institute and the Veterinary Service, to assess the possibility of establishing a tsetse-free zone in the Niayes region. The study found that 28.7% of cattle had serious health problems due to tsetse flies. After three years of piloting, training, preparation and population suppression, the release of sterile male flies began in 2012.
The scientific principle of fly contraception
The Sterile Insect Technique (SIT) is a pest control method that uses ionizing radiation to sterilize male flies that are mass-produced in special rearing facilities. The sterile males are systematically released from the ground or from the air into tsetse-infested areas, where they mate with wild females, who do not produce offspring. As a result, the technique can eventually eliminate wild fly populations. The Sterile Insect Technique is one of the most environmentally friendly control strategies and is often used as the last measure in a comprehensive campaign to eliminate insect populations.
The Joint FAO/IAEA Division supports some 40 SIT field projects implemented through the IAEA Technical Cooperation Programme, such as the one in Senegal, and in different regions of Africa, Asia, Europe and Latin America. The Division supported the successful eradication of the tsetse fly from Unguja Island in Zanzibar, while in Ethiopia, the Division reduced the tsetse fly population by 90 percent in parts of the Southern Rift Valley.
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