Scientists have found that there is no need to spray insecticide on walls for malaria control when people sleep under treated bed nets.
Use of insecticide sprayed on internal walls, when combined with insecticide-treated bed nets in homes, does not protect children from malaria any more effectively than using just insecticide-treated bed nets, researchers found.
The researchers led by Durham University and the Medical Research Council's Unit in The Gambia said this was important as insecticide-treated nets and insecticide sprayed on walls are commonly used for controlling malaria and in many places both interventions are used together.
Malaria is spread by mosquitoes that bite inside houses at night time so scientists working in The Gambia looked to see if children sleeping in homes that had the walls sprayed with the insecticide DDT, and also slept under an insecticide treated bed net, were sick less often with malaria than those who just used a bed net.
The study took place in 96 villages in The Gambia and 8,000 children were checked for malaria over two years. At the end of the study there was no difference in the numbers of cases of malaria where the combination of spraying and nets was used compared with the use of bed nets alone.
Using mosquito traps in houses the researchers confirmed that insecticide sprayed on walls had no extra effect in repelling or killing mosquitoes. The researchers recommend that DDT, or any other insecticide, is not used for spraying on walls in areas where there is high use of long-lasting insecticide nets and low to moderate numbers of malaria cases.
For the moment every effort should be made to make sure there is a higher use of bed nets, rather than on spraying insecticide on walls, scientists said. "Our advice is that high bed net coverage is sufficient to protect people against malaria in areas of low or moderate transmission," said Professor Steve lindsay, in the School of Biological and Biomedical Sciences, at Durham University.
"However, where net coverage is low, the cost-effectiveness of additional control using indoor residual sprays such as DDT should be considered," lindsay said. The research is published in The lancet.