Spraying Insecticide Indoors Reduces Spread of Malaria

Researchers in West Africa have shown that spraying insecticide indoors can dramatically reduce malaria transmission.

Efforts to develop a malaria vaccine have so far been disappointing, so programs to control the disease have focused on preventing transmission of the parasite. Insecticide-treated bed nets can prevent mosquito bites that spread the disease, but getting people to use them, and use them properly, is not always easy.

The fight against malaria has two main targets: the falciparum parasite itself, and the anopheles mosquito that carries the parasite from infected person to new victim.

Insecticides target the mosquito, but over time the insects develop resistance to the chemicals that kill them. That has been happening with current mosquito-killers, including chemicals known as pyrethroids.

Researcher Gil Germain Padonou and colleagues at the Centre de Recherche Entomologique de Cotonou in Benin tested another insecticide called bendiocarb with indoor spraying at test sites throughout Benin.

In households sprayed with bendiocarb, there were fewer mosquito bites. More importantly, none of the 350,000 people who lived there got malaria-infected mosquito bites during the test.

"And this is what this bendiocarb is all about, showing that it's efficacious - at least in this setting in Benin, in a real, live field setting" said Peter J. Hotez, who heads the American Society of Tropical Medicine and Hygiene, which published the research. "So it provides a potentially good alternative where there's been high development of resistance to pyrethroids."

Hotez says this demonstration of the effectiveness of bendiocarb doesn't mean that all malaria programs should adopt that particular chemical for spraying, or that indoor spraying should be the only strategy.

"When we think about a large-scale goal to take on malaria, it's not an either-or situation. We're going to have to throw multiple things out there in order to see what the optimal combination is to achieve control," said Hotez.

Bendiocarb is a widely used insecticide that is considered relatively safe when used properly. It has not been shown to be carcinogenic and is excreted rapidly by humans and other mammals. It is widely used for insect control against a wide variety of pests.