Skip to main content
Home » Malaria » Mosquitoes adapt their behaviour to resist insecticides

Mosquitoes adapt their behaviour to resist insecticides


Dr Nick Hamon

CEO IVCC and adjunct Professor of Entomology, North Carolina State University

Mosquito resistance to insecticide is threatening to undermine the global effort to eradicate malaria. A new generation of vector control products are needed if the disease is to be successfully stamped out.

The year 2000 marked a significant turning point in the development of malaria. The World Health Organization launched a global public health campaign to eradicate the disease. Since that time, an estimated 663 million clinical cases of malaria have been successfully averted. This success was often the direct result of ‘vector control’ products.

“Vector control has been the hero of the malaria success story to date,” says Professor Nick Hamon. “Insecticide-treated bed nets and indoor sprays are the main forms of vector control products and there is a real recognition of the role that the two have played in malaria reduction.”

Mosquitoes are learning to bite outdoors, away from sprays

Despite sustained efforts to eliminate the disease, malaria still claims the life of a child every two minutes.

In 2016, malaria was responsible for almost half a million deaths. Last year was the first year since 2000, where an annual drop in reported cases failed to occur.

“There is widespread mosquito resistance to one of the compounds used in the bed nets. It’s a similar story to the antibiotic one in humans. If you use the same product over time, it eventually loses its impact,” says Hamon. “There are multiple species of mosquitoes and, as they evolve, they adapt to the pesticide and become resistant.”

Stamping out insecticide resistance has now become an urgent priority. The hope, says Hamon, is that several new compounds can be developed that can be used to overcome the challenge of resistant mosquitoes, and reduce malaria reoccurrence rates in high-risk areas.

Mosquitoes are choosing to bite more outside

Bringing new insecticides to market is a long process, and one that is fraught with potential failure.

The disease is challenging to eradicate, not least because, for the companies who make insecticides, there will never be a financial return on investment on any products they develop.

Nick Hamon, IVCC

Because of the costs involved in formulating new insecticides, scientists are reliant on global crop protection companies allowing them to access their vast chemical libraries where the key to overcoming malaria resistance is likely to be found.

Crop protetcion companies have long been a driving force in the battle against malaria, supporting the research, development and maintenance of insecticide supplies, says Hamon. And they have saved millions of lives in the process.

“We work very closely with a number of global companies, screening their chemical libraries for potential compounds that might provide us with solutions to resistance. There are a number of new compounds already in pre-development, and we hope to get some of them into full development by 2021,” he says. “If that proves successful, it could give us a whole new suite of malaria interventions.”

With scientists in possession of additional insecticides, the active ingredient used in bed nets and indoor sprays can be used in rotation to overcome, or at least slow down, resistance. It is also hoped that new compounds can be developed to help control the spread of malaria outdoors.

“Mosquitoes have adapted to indoor insecticides by altering their behavior and becoming more active outside, in the open air,” says Hamon. ‘It’s crucial therefore that we develop products that can be used by people who work outdoors, who are travelling in affected areas, or anywhere that there are migrant populations or refugee camps.’

Insecticide development can be slow to market

As with the development of any new drug or compound, the testing stage of new insecticides comes without guarantees. Stringent safety and environmental measures are in place, and bringing new products to market takes a considerable amount of time.

When it comes to the future of malaria though, Hamon is hopeful.

“We have an exciting pipeline of products in development that could prove to be game-changing. Eradication is possible,” he says. “We’ve successfully managed it in most areas of the world, and by integrating drugs and vaccines with new vector control products, we can get rid of the disease for good.”

Next article