Indoor residual sprays

Indoor Residual Spraying (IRS) is the technique of applying a residual deposit of an insecticide onto indoor surfaces where arthropod vectors rest.

The primary goal of indoor residual spraying is to reduce the lifespan of the vectors and thereby reduce or interrupt disease transmission. The secondary impact is to reduce the density of vectors within the treatment area. IRS is a recognised, proven and cost-effective intervention method for the elimination of malaria and it is also used in the management of Leishmaniasis and Chagas disease.


Key assumptions within an effective IRS program are that:

• there are a high number of sprayable surfaces within each dwelling
• that the vector species in question feeds and rests indoors
• that the vectors are not resistant to the insecticide which is being applied
• a large number of dwellings within the target area can be sprayed.

Other important considerations within an IRS campaign:

• the safety of the product to the operator
• the residents and the environment
• the residual efficacy of the product; the level of acceptance of the product by the residents (eg: due to odour or staining)
• cost effectiveness (which is also related to residual lifespan)
• logistical hurdles associated with the geography of the area (eg:. some older IRS products require very high dose rates and thus large volumes of concentrate are required compared to more modern lower-dose products).
• transmission dynamics within the treatment area as they have an influence on the frequency of application required and/or the desired residual lifespan of the product chosen (eg: in situations of unstable transmission where epidemic malaria occurs, the lifespan of IRS products would not need to be as long, or the frequency of application would be less, compared to areas where stable hyper-endemic malaria occurs).

Environmental Science offers the following insecticides for IRS (as recommended under the WHO Pesticides Evaluation Scheme):

Further details for each of these products can be found on their respective product pages on this website.

In addition to these products we are also investing in the development of new IRS solutions, focussing on addressing the challenges of residual activity and insecticide resistance management.