Intoxicating: Tsetse flies are drawn to the odours of lizards and pigs

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A tsetse fly that transmits sleeping sickness has a penchant for lizard and pig odour — a preference that could be used to produce traps to control fly populations.

Sleeping sickness, or African trypanosomiasis, affects around 300,000 people a year in Africa and can be treated only with toxic and hard-to-administer drugs.

Scientists are investigating using insecticide-treated traps baited with attractive odours to control fly populations but so far no strong, artificial attractant has been developed for Glossina fuscipes, the species of tsetse fly that predominantly transmits the sleeping sickness parasite Trypanosoma brucei gambiense in West Africa.

The lack of artificial attractants means that existing traps are weak and more are required in a given area, making them an expensive option.

Researchers, including groups from the International Centre for Insect Physiology and Ecology in Kenya and Labovet in the Democratic Republic of Congo, assessed whether two Glossina subspecies — G.f. fuscipes and G.f. quanzensis — were attracted to the odours of their natural hosts: humans, pigs and cattle. They also tested whether G.f. fuscipes was attracted to the odour of its other host, the lizard.

They extracted air from chambers separately containing each of the hosts and tested how effective odours taken from the air were as bait in traps.

Neither fly was attracted to human or cattle smells but lizard odour-traps caught twice the number of G.f. fuscipes flies caught in regular traps, and G.f. quanzensis was attracted to pig odour.

The researchers write that identifying the components in the lizard and pig odour that the flies are attracted to will improve the performance of traps.

Co-author Jean Baptiste Rayaisse, from the International Center of Research and Development on Breeding in Sub-Humid Areas, Burkina Faso, says that the team will continue to work on developing attractive odours.

"If we keep working hard, we'll be able to develop more effective substances and fighting against sleeping sickness will become less costly," he says.

The research was published in PLoS Neglected Tropical Diseases in May.

Link to full paper in PLoS Neglected Tropical Diseases