"This could be used in more effective traps to capture tsetse flies," John Carlson, co-author of the study revealing these results, published Thursday in the journal Science, told AFP.

Tests are already planned in Kenya, added this professor of biology at Yale University.

Tsetse flies, which are only found in sub-Saharan Africa, transmit trypanosomiasis, a disease affecting both humans (human African trypanosomiasis, better known as sleeping sickness), and livestock (nagana) .

It poses a threat to millions of people in dozens of countries, and causes the death of around three million farm animals each year, representing a direct loss of up to 1.2 billion dollars per year, according to an independent commentary article published simultaneously in Science.

It is thus a major cause of rural poverty in this region.

Source of concern: the geographical area where they evolve could also expand due to climate change, notes the study.

Despite more than a century of research on this animal, the chemical communication of tsetse flies remained poorly understood, and scientists had never succeeded in identifying volatile pheromones in them (acting at a distance).

However, pheromones are already used against other insects, such as certain moths.

Pheromones are a chemical substance emitted by an animal, having an effect on the behavior of congeners.

They allow insects to recognize each other in an environment where thousands of other species potentially evolve.

Bait

For their research, the scientists bathed tsetse flies for 24 hours in a solvent.

The extracts were then applied to fly-shaped lures.

Only the extracts of female flies attracted the males placed in the presence of the lures.

The researchers then used an analytical technique (combining chromatography and spectrometry) to isolate several chemical compounds.

After multiple tests, they determined that one of them acted as an aphrodisiac, and was detected by the males' antennae, activating their olfactory neurons.

"It's not only a bait, but it also causes the fly to come to a standstill, it stops moving," explained John Carlson.

A property that would help keep them in traps.

Traps are already one of the techniques used to regulate the population of tsetse flies, but they currently use animal odors to attract them.

“We expect pheromones to improve trap efficiency,” said John Carlson.

In addition, the chemical compound identified "is less volatile than the animal odors currently used, and therefore would remain in the traps longer".

However, the type of pheromone identified in this study should not be effective against all species of tsetse flies.

The study focused on a species (Glossina morsitans) an important vector of the disease for cattle.

But the tests proved less conclusive on another species (Glossina fuscipes), associated with the highest number of cases of disease in humans, according to the researchers.

However, they hope that the technique developed will allow them to identify comparable pheromones that can work for this second species.

© 2023 AFP