Two major mosquito species that carry malaria are developing resistance to insecticide through their feet. A new study reports on how this impacts the efficiency of anti-mosquito nets, anti-malaria efforts, and a potential way forward.

Binding proteins in the feet of Anopheles gambiae and Anopheles coluzzii mosquitoes are helping them resist the insecticides embedded in mosquito nests, explains the team at the Liverpool School of Tropical Medicine (LSTM). As these species represent two of the most important malaria vectors in West Africa, it could undo “decades” of progress against the disease.

Net gonna get me

“We have found a completely new insecticide resistance mechanism that we think is contributing to the lower than expected efficacy of bed nets,” explains Dr. Victoria Ingham, first author. “The protein, which is based in the legs, comes into direct contact with the insecticide as the insect lands on the net, making it an excellent potential target for future additives to nets to overcome this potent resistance mechanism.”

The team found higher than average levels of the binding protein SAP2 in the insecticide-resistant species of Anopheline mosquitoes. These levels elevated further elevated levels following contact with pyrethroids, the class of insecticides used in bed nets. However, when the genes encoding this protein are partially silenced, the insects lost their resistance to pyrethroids.

As insecticide resistance grows across mosquito populations, the team explains, new insecticide-treated bed nets containing the synergist piperonyl butoxide (PBO) and pyrethroids are being introduced. Such netting targets one of the most effective and widespread resistance mechanisms mosquitoes posses, but they are always evolving new ones. The authors hope that their discovery could help point to other potentially dangerous adaptations by mosquitoes.

“Long-lasting insecticide treated bed nets remain one of the key interventions in malaria control,” explains Professor Hilary Ranson, the paper’s senior author.

“It is vital that we understand and mitigate for resistance within mosquito populations in order to ensure that the dramatic reductions in disease rates in previous decades are not reversed.”

The paper “A sensory appendage protein protects malaria vectors from pyrethroids” has been published in the journal Nature.