Insecticide Resistance Management (IRM)

Managing insecticide resistance is complex, in part because resistance takes a variety of forms, therefore local strategies must be tailored to the type of resistance present. The two main mechanisms—metabolic resistance and target-site resistance—include multiple forms, which are of varying importance for different classes of insecticide.

A further complication is ‘cross-resistance’ between insecticides that have the same mode of action for killing mosquitoes. For example, vectors that are resistant to pyrethroids will probably also be resistant to DDT. Cross-resistance restricts the choice of alternative insecticide available for resistance management.

Resistance can be delayed by regularly changing insecticides and developing strategies which rotate or mix different insecticides with different modes of action but there are several challenges. Firstly, there is a limited range of chemistries approved for use in vector control so the insecticides which are available must be used rationally to prolong their effectiveness. Secondly, IRM strategies should be tailored specifically to the resistance profiles in each area to maximise their impact.

The goal of the international health community is to reduce the global malarial burden and eradicate the disease as soon as possible. Increasing insecticide resistance, heavy reliance on pyrethroids and limited alternatives in the market all pose a significant risk to this ambition. There is a collective responsibility to maintain the susceptibility of malaria vectors to the insecticides in use today, and to develop new active ingredients with new modes of action for use in Integrated Vector Management (IVM) toolboxes as resistance inevitably develops over time.