Commercial partner sought to develop new anti-mosquito nets

Malaria remains one of the most devastating transmissible diseases. The protection recommended by the World Health Organisation for people at risk of getting bitten by infected mosquitoes is the use of nets impregnated with pyrethroid insecticides. Unfortunately, excessive and inappropriate use of this insecticide has led to a disturbing rise in the number of resistant insects, meaning that mosquito nets treated with pyrethroids are losing their effectiveness. It is therefore essential to devise new control strategies against resistant mosquitoes.

Now researchers at Institut de Recherche pour le Developpement in Paris and their partners have obtained encouraging results by combining a non-pyrethroid insecticide, propoxur, and a repellent, N,N-diethyl toluamide. A combination of the two insecticides has been demonstrated to be more effective than using either alone. Mosquito nets soaked with this mixture knock down mosquitoes on contact and have an irritant effect that inhibits the mosquitoes from biting.

The nets have been tested in field trials in the rice-growing area 40 km North of Bobo-Dioulasso, in Burkina Faso, where two different forms of mosquito (Anopheles gambiae) occur.

The first appears in May and June in the rice-fields. It shows no resistance to pyrethroids. The second emerges in September and October in puddles left by monsoon rains. These do show resistance to these insecticides. As expected, the usual pyrethroid-treated nets turned out to be effective only against non-resistant mosquitoes of the first population.

Nets pre-soaked with non-pyrethroid–repellent combinations provided protection for the people of the local villages, whatever the population of mosquitoes present.

However, the nets are only effective for about 15 days and the researchers would like to find a company able to devise a system for encapsulating the mixture to make the nets effective for longer.

The research was carried out at  IRD laboratory at Cotonou, Benin, with the participation of the Centre de Recherches Entomologiques de Cotonou, IRD’s Laboratoire de Lutte contre les Insectes Nuisibles in Montpellier, and the Institut de recherche en science de la santé, Bobo-Dioulasso, Burkina Faso.