Combinations of Insecticide-Treated Nets and Indoor Residual Spraying for Insecticide Resistance Management: A Modelling Exploration

Insecticides are heavily used for the control of vectors of disease. Malaria control has been reliant on insecticide treated nets (ITNs) and indoor residual spraying (IRS). There are concerns insecticide resistance will impede malaria control. The use of insecticide resistance management (IRM) strategies is recommended. One proposed IRM strategy is the combination of ITNs and IRS. Using a mathematical model of polygenic insecticide resistance evolution, this combination strategy is evaluated. First, combinations are evaluated against ITNs alone to determine if and when combinations may be beneficial in slowing resistance evolution to the pyrethroid on the ITN. Second combinations where multiple IRS insecticides are available are compared against full-dose mixture ITNs. Results of the simulations indicate the addition of IRS to ITNs may be beneficial, providing coverage of both interventions is high. The greater number IRS insecticides available for rotation the better, however even when combinations rotate three different IRS insecticides this is still a less potent IRM strategy than deploying full-dose mixtures. In conclusion the combination of ITNs and IRS appears to offer limited benefit over full-dose mixture ITNs for an IRM perspective