Insecticides help control insect-borne diseases but resistance to chemicals can reduce their impact

USAID

Assay methods to monitor insecticide resistance must evolve and adapt, say Gregor J. Devine and Elena Ogusuku.

Insecticides are crucial for controlling insect-borne diseases such as dengue fever but resistance to chemicals can reduce their impact.

Bioassays are biological experiments that measure the lethal effects of insecticides against field-caught mosquitoes. They provide fast and cheap ways to detect insecticide resistance in mosquito populations and can help inform vector control programmes.

But the two bioassays currently available — the WHO assay and the bottle assay — have not been updated since 1998 and desperately need to be improved and altered to be more robust and globally relevant, say the authors.

Neither bioassay is universally suitable. The WHO assay requires all components to be bought from a centralised source, which increases its costs and limits its use. Some of the bottle assay components are more readily available, but it relies on using pure insecticide, which is expensive and often inaccessible.

A project in Peru has demonstrated that small, peer reviewed changes can help improve assays. For example, adapting assays to use ethanol to bypass South America's tight acetone regulations, or using local insecticide formulations instead of technical grade insecticide, made them quicker and more manageable.

Local laboratories should be encouraged to adapt and modify assay protocols to suit local conditions and needs, say the authors. These should be published so that they can be peer reviewed and adopted by others.

Link to full article in Bulletin of the WHO