Core vector control methods
Vector control is a fundamental element of the existing global strategy to fight malaria. Vector control interventions have a proven track record of successfully reducing or interrupting disease transmission when coverage is sufficiently high. Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the two most important vector control measures that protect humans from the bite of malaria-carrying mosquitoes.
WHO recommends that endemic countries protect all persons at risk of malaria through LLINs or IRS, or a combination of the two interventions (where it is justified). Vector control strategies should be drawn up in consideration of changing insecticide resistance patterns and through an integrated vector management (IVM) approach, which seeks to improve the efficacy, cost-effectiveness, ecological soundness and sustainability of disease vector control.
Indoor residual spraying
IRS reduces malaria transmission by reducing the survival of mosquitoes that enter houses or sleeping units. It involves spraying an effective dose of insecticide, typically once or twice per year, on indoor surfaces where malaria vectors are likely to rest after biting. IRS is a method for community protection and, to achieve its full effect, IRS requires a high level of coverage in space and time. Globally, an estimated 5% of the population at risk is protected by IRS.
WHO Pesticide Evaluation Scheme (WHOPES) currently recommends 12 insecticides belonging to 4 chemical classes for IRS. National malaria control programmes need to select insecticides for a given area on the basis of the residual efficacy of the insecticide; costs, safety and the type of surface to be sprayed; and up-to-date insecticide resistance data. DDT has a comparatively long residual efficacy, lasting more than 6 months, and continues to be a widely used insecticide for IRS. The use of DDT in agriculture is banned under the Stockholm Convention on Persistent Organic Pollutants but countries can use DDT provided that the guidelines and recommendations of WHO and the Stockholm Convention are all met, and until locally appropriate alternatives are available for a sustainable transition from DDT. WHO’s position statement on DDT (2011) is linked from this page.
Long-lasting insecticidal nets
LLINs last longer than conventional insecticide-treated bed nets, but still need to be replaced regularly. LLINs provide both a physical barrier and an insecticidal effect to reduce human-mosquito contact. They also have an important community effect as their community use leads to large-scale killing of mosquitoes. Between 2000 and 2012, the proportion of households owning at least one bed net in sub-Saharan Africa increased from 3% to 53%. In the last two years, however, the number of bed nets delivered to sub-Saharan African dropped significantly, foreshadowing the possibility of malaria resurgences in the coming years unless urgent action is taken.
Managing insecticide resistance
Mosquito resistance to public health insecticides has been identified in 64 countries around the world, affecting all major vector species and all classes of insecticides. Most affected countries have not yet carried out adequate routine testing, which means that our understanding of the scale of insecticide resistance is incomplete. Endemic countries are therefore urged to draw up and implement comprehensive insecticide resistance management strategies and ensure timely entomological and resistance monitoring.
Issued in May 2012, the Global plan for insecticide resistance management in malaria vectors (GPIRM) contains a global plan of action for all stakeholders engaged in the fight against malaria. It also contains comprehensive technical recommendations for managing insecticide resistance in different situations – including on the use of insecticide rotations for IRS.
Last update: 6 March 2013
- WHO guidance for countries on combining indoor residual spraying and long-lasting insecticidal nets (2014)
- Indoor residual spraying: An operational manual for IRS for malaria transmission, control and elimination (2013)
- WHO recommendations for achieving universal coverage with long-lasting insecticidal nets in malaria control (2013)
- Global plan for insecticide resistance management in malaria vectors (2012)
- The use of DDT in malaria vector control: WHO position statement (2011)
- WHO position statement on integrated vector management (2008)