Since 2005, over 2 billion insecticide-treated nets (ITNs) have been distributed worldwide to prevent malaria. All of these nets were treated with only one insecticide class – pyrethroids. However, as mosquitoes in many areas are now resistant to pyrethroids, nets treated with other active ingredients are needed to control malaria.

In 2017, WHO started to recommend a new type of ITN that combines pyrethroids with piperonyl-butoxide (PBO), a chemical that enhances the potency of pyrethroids against resistant mosquitoes.

New recommendations, published today in the WHO Guidelines for malaria, cover 2 new classes of dual ingredient ITNs with different modes of action:

• Pyrethroid-chlorfenapyr nets combine a pyrethroid and a pyrrole insecticide to enhance the killing effect of the net.
• Pyrethroid-pyriproxyfen nets combine a pyrethroid with an insect growth regulator (IGR). The IGR disrupts mosquito growth and reproduction.

“These new types of nets were designed to have a greater impact against pyrethroid-resistant mosquitoes,” notes Dr Jan Kolaczinski, who leads the Vector Control and Insecticide Resistance unit within the WHO Global Malaria Programme. “By including two active ingredients in an ITN, the likelihood of mosquitoes being resistant to both is greatly reduced.”

Read the details here in the newest WHO Malaria Guidelines