Indoor Residual Spraying (IRS)

Together with long lasting insecticidal nets, indoor residual spraying (IRS) is a highly effective tool in preventing malaria. IRS involves spraying a long lasting insecticide on the interiors of animal shelters or human habitations. When searching for blood meals, mosquitoes rest on internal surfaces of structures such as walls and ceilings and are subsequently killed or repelled by the insecticide. 

IRS is most effective when implemented after the anopheles mosquito feeds as this is when the mosquito is most likely to rest on a sprayed surface, receiving a lethal dose of insecticide. There therefore must be mass coverage of homes, structures and shelters with IRS for it to be fully effective and all potential interior surfaces must be covered with insecticide. For instance, little impact will be made if only one structure or wall is sprayed.

LLINs prevent the mosquito from feeding before the mosquito can transmit a disease and combined with IRS, a highly powerful approach to fighting malaria is created.

It is vital that IRS campaigns are deployed in a targeted manner with a strategic approach to implementation. Programme managers have to consider the cost, logistics, where IRS should be deployed and how IRS affects other vector control measures (such as LLINs).