The best tool we have to prevent malaria is losing its power

Malaria’s worst enemy.
Malaria’s worst enemy.
Image: Reuters/Thierry Roge
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Malaria may have finally been defeated in Europe—there haven’t been any cases there in the past year—but it still remains among the 10 main causes of death worldwide according to the World Health Organization (WHO).

While there has been a reduction of malaria cases of up to 75% in 72 countries, Deutsche Stiftung Weltbevoelkerung (DSW), an organization working on health in developing countries, warns that 590,000 people get infected with malaria every day, and WHO data show that there are currently over 200 million malaria cases in the world, with the predominance (90%) in Sub-Saharan Africa.

While there are treatments for malaria, and vaccines are being developed, the most effective way to control malaria has been by stopping the carrier, the Anopheles mosquito, most commonly with insecticidal bed nets.

Currently, an estimated 50% people in African countries where malaria is endemic sleep under insecticide-treated bed nets, which are credited as arguably the most effective control measure against malaria transmission. According to a study published in Nature in October 2015, long-lasting nets are responsible for 68% of the decrease in malaria cases since 2000.

The impact has been enormous—but it’s slowing down: “we’re seeing now, and we’ve mapped out in 64 countries, that the efficacy of bed nets is reducing,” Mikkel Vestergaard, CEO and owner of Vestergaard, the first developer and world largest producer of long-lasting bed nets, told Quartz. In spite of the wide-scale distribution of nets, increases in malaria rates have been seen in countries including South Sudan, Gambia, and Burkina Faso, which might be due to mosquitoes developing resistance to pyrethroid, the class of insecticide that the bed nets are treated with.

The good news is, there is a solution. Or there could be.

Vestergaard developed a new type of net, treated not only with pyrethroid, but with piperonyl butoxide, too. Helen Pates Jamet, the head of entomology at Vestergaard, said the compound “works by blocking the metabolic enzymes within the mosquito that break down the insecticide,” making it resistant to it. Essentially, it blocks the insecticide blockers—though it’s hard to tell if it further resistance can be developed.

The net was submitted to the WHO for evaluation in 2007, but it took seven years for WHO’s vector control advisory group to review the data set, and finally recommend the product in 2014.

The WHO has asked for further trials before the piperonyl butoxide-treated nets replace the existing ones in the various net distribution programs happening across Africa. Further, the WHO has encouraged (pdf, p. 2) the industry to fight resistance by developing nets that are treated with a different class of insecticide.

This, however, will likely take years: so far, pyrethroid is the only class of insecticide approved for usage on fabric. In the mean time, Vestergaard laments, the WHO is wasting time by delaying the introduction of a product that could fight mosquito resistance. On the other hand, the WHO says current nets are still doing an OK job at keeping mosquitoes at bay—even if they have developed resistance, a spokesperson told The Guardian, they still work as a barrier to stop mosquitoes.

A recent study published in Parasites and Vectors found that while mosquitoes have developed resistance, insecticides are still active on the parasites inside them, reducing the risk of infection.