The chemical that squeezes the wings increases the effectiveness of the mosquito nets

In many parts of the world, insecticide-treated bed nets are used not only to prevent malaria-carrying mosquitoes from biting, but also to kill them. A new study now shows that these mosquito nets could be much more effective if another type chemicals were used.

Currently, a class of insecticides known as pyrethroids are applied to mosquito nets for use in regions such as sub-Saharan Africa. The idea is that when the insects come into contact with the toxic fabric, they die on contact – or soon after. Unfortunately, mosquitoes develop resistance to pyrethroids, which makes the chemicals less deadly.

In search of a more effective alternative, scientists at the National Institute of Medical Research in Tanzania turned to a pesticide called chlorfenapyr. Instead of killing mosquitoes instantly, this causes their wing muscles to cramp, preventing them from flying. Because they can’t fly to locate their prey, they can’t feed themselves, so they end up starving.

Led by lead researcher Jacklin Mosha, the team conducted a study involving 4,500 children in the Misungwi district of Mwanza region in Tanzania. Increasingly high levels of resistance to pyrethroids have been reported in this region.

The children were divided into four groups, each using either standard pyrethroid-treated nets; fillets in which piperonyl butoxide has been added to a pyrethroid, to increase the potency of the latter; mosquito nets treated with a pyrethroid and pyriproxyfen, the latter sterilizing female mosquitoes; and mosquito nets treated with chlorfenapyr.

It was found that after 24 months, the group that slept under the chlorfenapyr nets every night had a 37% lower rate of malaria infection than those who used the standard or pyriproxyfen-reinforced pyrethroid nets. The group that used the piperonyl butoxide-reinforced pyrethroid nets experienced a 27% reduction in malaria infection after the first 12 months, but this figure fell to a level similar to that of the standard nets after two years .

“Based on this evidence, the National Malaria Control Program and WHO [World Health Organization] can update current national malaria control strategies and include an effective new tool,” said Mosha. “It is also essential that donors and governments fund these more effective tools.

Source: SciDev.Net

Sara H. Byrd