Residual surface sprays are used in a variety of settings – for example as indoor residual spraying (IRS) for malaria, leishmaniasis or Chagas disease control or targeted indoor residual spraying (TIRS) or targeting outdoor spraying (TORS) for dengue prevention.
The relevance of residual spraying very much depends on the resting behaviour of the target vector. The goal of residual spraying is generally to reduce the average lifespan of the mosquito population and limit their capacity to transmit disease. A secondary benefit, when applied at scale is to reduce the density of vectors within the treatment area.
Key assumptions within an effective RSS program:
- there are a high number of sprayable surfaces within each dwelling
- the target vectors feed and rest indoors
- the vectors are susceptible to the insecticide which is being applied
- a large number of dwellings within the target area can be sprayed (usually minimum of 80% coverage required)
Other important considerations within a RSS campaign:
- the safety of the operator, household residents and the environment
- the residual efficacy of the product
- cost effectiveness (which is also related to residual lifespan)
- the level of acceptance of the product by the residents (e.g. due to odour or staining)