To the uninitiated, the phrase ‘IRS’ may at first appear confusing or complex. It may look as if it’s an acronym for a scientific compound. Photographs of individuals wearing what look like hazmat suits, entering homes in malaria-endemic regions add to the confusion.
But in reality, the concept of IRS is simple. IRS stands for Indoor Residual Spraying and involves the application of insecticide to the inside of dwellings, on walls and other surfaces. These surfaces are notorious as they are often breeding sites for malaria-infected mosquitoes.
The spraying of insecticide reduces the vector population by killing mosquitoes when they come into contact with treated surfaces. By keeping the vector population low, mosquitoes are less likely to reproduce. It also means that humans are less likely to be bitten by infected mosquitoes, reducing malaria transmission.
Malaria transmission is most prevalent during rainy seasons when small pockets of water appear, mosquitoes use these small wells to lay their eggs.
The practice of Indoor Residual Spraying is usually conducted by health workers or charity organisations who are responsible for protecting a particular area. International aid organisations, such as the President’s Malaria Initiative, conduct regular IRS programmes to stop the spread of malaria.
You can learn more about the President’s Malaria Initiative’s efforts to end malaria through IRS in our interview with one of their scientists.
IRS is a proven, effective and low-cost way of reducing transmission and can be used alongside other preventative measures, including insecticide-treated bed nets and other novel solutions.
There has been a significant reduction in malaria transmission over the past fifteen years. This is in part to the introduction of insecticides to reduce the vector populations in Sub-Saharan Africa. But, due to a lack of routine monitoring for insecticide resistance in local vectors and monitoring data not being reported in a timely manner, resistance to the current insecticides is growing.
Mosquitoes are currently resistance to all four recommended classes of insecticide. Since 2010, a total of sixty-one countries have reported resistance to at least one class of insecticide, with fifty of those countries reporting resistance to two or more classes.
If action is not taken promptly, the issue of resistance could lead to a substantial increase in malaria incidence and mortality.
A New Solution
To combat the issue of growing insecticide resistance, the global stakeholder community is working together to find a solution. Following guidance from the World Health Organisations, the complex issue of resistance is being addressed.
Professor Steve Lindsay of Durham University has trialled a new type of mosquito bed net in Burkina Faso with promising results. The new type of mosquito net contains two active ingredients: permethrin and pyriproxyfen, the two together work better than a single treatment. You can learn more about his work by listening to Five Minutes with Professor Steve Lindsay.
To educate health workers overseas in a more accessible and fun way, a team of scientists from the Liverpool School of Tropical Medicine have developed a mobile game called Resistance 101. The app is free to download and is available on both iOS and Android devices.