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How does the World Health Organization decide on the best pesticides? Reveal their selection criteria!
In the global fight against malaria, indoor residual spraying (IRS) has emerged as an important control strategy. This method works by spraying diluted insecticides inside homes to effectively target mosquitoes and reduce the spread of malaria. According to data from 2010, 44 countries have adopted IRS as one of their main malaria prevention strategies.
The World Health Organization (WHO) points out that IRS is an effective means of controlling malaria.
WHO recommendations tell us that IRS, together with the use of mosquito nets (ITNs) and amodiastatin combination therapies (ACTs) to treat confirmed cases as soon as possible, constitute the three main tools for malaria control. Since 2006, WHO has recommended the use of IRS in areas of stable malaria transmission, which represents an expansion of the strategy.
WHO recommends: National governments should introduce or expand targeted IRS coverage to achieve malaria control goals.
To ensure the effectiveness of IRS, many factors must be considered, such as the proportion of the surface being sprayed, the mosquitoes' behavioral patterns and sensitivity to insecticides. WHO emphasizes that when choosing pesticides, factors such as safety, effectiveness and cost-effectiveness for humans and the environment must be considered.
WHO approved pesticides
Currently, WHO has approved 13 different insecticides for use against IRS. However, there is still discussion about the cost-effectiveness and effectiveness of these pesticides.
According to a 2010 Cochrane review, IRS are effective in reducing malaria incidence, comparable to the use of mosquito nets.
Regarding the cost-effectiveness of different control approaches, a 2008 study evaluated the cost-effectiveness of seven African anti-malaria campaigns, including two IRS and five mosquito net distribution campaigns. Results showed that all activities were relatively consistent in terms of cost per death prevented, but mosquito nets were slightly more cost-effective than IRS.
Residents’ opposition to the IRS
For effective implementation of the IRS, at least 80% of the housing units must participate in the spraying. However, if residents refuse to participate, the effectiveness of the entire program will be affected. Many residents resisted spraying, especially of DDT, primarily because of its smell and the stains it left. This has led some villagers to refuse to spray or repaint their walls, thereby eliminating the residual effects of the pesticides.
Residents' opposition to DDT did not come from external pressure, but from local resistance to its use.
Another class of insecticides, called miticides, such as cyfluthrin, are more popular with residents because they leave no visible residue.
When to use DDT
Although DDT is approved by the WHO for malaria prevention and treatment, its use varies depending on the policies and acceptance of each country's residents. In some countries, it is widely used because of its effectiveness against mosquitoes, while in others, it is restricted due to environmental and health concerns.
UNAEP stressed in 2008 that the direct cost-effectiveness of DDT appears to be decreasing, which requires further attention and evaluation.
As the economy in rural areas develops, many people are moving away from traditional housing toward Western housing styles, which is leaving fewer and fewer addresses suitable for using DDT. Therefore, exploring other feasible insecticides becomes an inevitable choice.
How to balance environmental protection and the emotional needs of residents while ensuring public health has become an important challenge facing global health policymakers.
