French and Senegalese researchers were able to eradicate a population of tsetse flies, a sleep-sickness carrier, in the most populous region of Senegal's men and cattle.
For this, they gradually dropped sterile males using a radiation technique. A method that, applied in nature, requires ethical reflection.
This Saturday, December 8, the President of the Republic of Senegal, Macky Sall, will officially announce the success of the eradication of the tsetse fly in the coastal area of Niayes, a small area on the surface (1 000 km2), but dense in human population and in cattle.
Work began in 2007, coordinated by Jérémy Bouyer, veterinary entomologist at the Center for International Cooperation in Agricultural Research for Development (CIRAD), currently at the International Atomic Energy Agency (IAEA) of Vienna (1).
A brake on livestock development
The tse-tse fly, or tsetse fly, transmits trypanosomes that cause parasitic diseases in humans who develop "sleep sickness", which can be fatal in the absence of treatment, as well as in cattle. .
In these cases the infection causes a decrease in fertility, weight loss and sometimes death. But tsetse flies significantly limit reproduction improvements throughout sub-Saharan Africa, as in Senegal, where 80% of the milk consumed is imported.
Rereading: the fly, the best enemy of man
The technique of the sterile insect
Previously, the researchers made sure that the tse-tse fly population was well-isolated, that it did not receive flies from another wild population. The researchers also conducted socioeconomic studies and surveys on herds.
In 2012, the introduction of insecticide traps and cattle treatments reduced the tsetse fly population. Hence the release of sterilized males with an irradiation technique (ionizing rays that neutralize the genitals, but which in no case do radioactive flies) have destroyed the last wild flies. The irradiated pups (nymphal stage) come from Bobo-Dioulasso (Burkina Faso).
This sterile insect technique has proven effective in controlling many insects or insect vectors such as fruit flies, as well as against screwworm that attacked farm animals in the 1980s in the United States. and in Libya and in the 1990s in Central America. " At the start of the project, almost 100 tsetse flies a day and traps were captured at some sites, recalls Jeremy Bouyer, just before July we found one or two a month. Today is zero! "
Rereading: a hope in the fight against tsetse flies
Increased livestock production and extension into a larger area
The eradication of tsetse flies allows shepherds to get rid of low-production and disease-resistant cows to breed better-performing breeds of milk and meat. This favorable zootechnical environment should lead to an annual production increase of 2.8 million euros per year, according to the estimates of the parallel impact study of the project. Another already visible spin-off is the reduction of cultivated areas by farmers: an important issue in a context of soil pressure.
Based on the success of this eradication program, the Senegalese authorities are planning an extension to an area of 5,000 km2 of Sine Saloum, a delta located south of Petite-Côte, formed by the confluence of Sine and Saloum .
In this region, the problem of tsetse flies is even more important because flies transmit two species of trypanosomes, one of which is much more virulent.
These results are part of a major campaign to eradicate the pan-African tsetse (Pattec) launched in 2001 across the continent, particularly in Burkina Faso, Guinea and Senegal. " CIRAD has played a role in the production of knowledge, training and capacity building, but also by creating a multi-stakeholder partnership that includes policy makers Explains Sylvie Lewicki, regional director of CIRAD West Africa – dry area.
Rereading: towards the eradication of the tsetse fly in Senegal
Ethical issues and impacts on biodiversity
Throughout the eradication program, Jérémy Bouyer and his colleagues paid close attention to the impact of their actions on biodiversity. " We have carried out a very accurate environmental monitoring, thanks in particular to the relevant bioindicators.explains the researcher. We observed a slight loss of biodiversity during the period of treatments with insecticides, so a return to normal ".
Finally, " if global tsetse eradication is not ethically justified, localized elimination campaigns targeting isolated populations are ethically defensible ".