WASHINGTON — A nuclear technique developed with the support of two United Nations agencies successfully suppressed the disease-carrying tsetse fly in Senegal without harming other insects, the U.N.’s nuclear watchdog agency said on Friday.
The results of an eight-year study of the tsetse fly in Senegal, published in Nature’s Scientific Reports, is part of a project to help the West Africa nation eradicate tsetse in Niayes, a 1,000 square-kilometer fertile valley near the capital Dakar.
Senegalese researchers, with funding from the United States government, collaborated with the International Atomic Energy Agency and Food and Agriculture Organization. Their study used insecticide-impregnated traps followed by the application of an insect birth control method known as the Sterile Insect Technique, IAEA said in a statement.
The technique, called SIT, uses radiation to sterilize male flies that are raised in large numbers and released to mate with wild females. They produce no offspring, decreasing the population over time. Researchers monitored flower chafer beetles and leafwing butterflies to show the eradication campaign had little effect on populations. Minor fluctuations were seen when insecticides were used to apply SIT.
Beetle and butterfly populations reverted to pre-intervention levels when use of the insecticide ended and release of sterile male tsetse flies began, showing SIT does not harm the environment, IAEA said.
“Any control action carried out in the environment, with or without the use of insecticides, requires an environmental impact study,” said IAEA medical entomologist and study co-author Jeremy Bouyer. “The study proves that SIT is an environmentally-friendly method, and that we succeeded to almost eliminate tsetse without impacting the ecosystem.”
— IAEA – International Atomic Energy Agency (@iaeaorg) January 10, 2020
Beetle and the butterfly
The tsetse fly sucks blood while transmitting parasites that cause nagana, a wasting disease in cattle. It leads to infertility, weight loss and reduced milk and meat production. In some parts of Africa, the tsetse fly also transmits human sleeping sickness, a debilitating and frequently deadly disease.
The IAEA, in cooperation with FAO, has been helping Senegal suppress the tsetse fly in the Niayes region since 2005. That has helped local farmers hold onto imported cattle breeds that can produce 10 times as much milk as local breeds.
Researchers said they chose the beetle and butterfly for the study because they are cost-effective, reliable indicators of the effects of agriculture, hunting and other human-caused pressures on the environment. The beetle and butterfly also do not pollinate plants or serve as an essential prey to birds and insects.
Fruit traps were laid out in five places for a week at a time during the course of the eight-year study. That was always done in October and November, during the rainy season when the insects have more diversity and density. More than 14,400 insect specimens were then identified, counted and analyzed.
“The impact of suppression efforts on the environment is minimal and temporary and the considerable decrease of tsetse — more than 98 per cent — is very encouraging.” said study co-author Mireille Bassene, a medical entomologist at Senegalese Institute of Agricultural Research, which also participated in the project.