Researchers say theyve found a DDT replacement

Anopheles gambiae, a malaria-bearing species of mosquito native to Africa.

Courtesy Wikimedia

Scientists working in Africa think they have found an insecticide that can kill malaria-bearing mosquitoes as effectively as DDT.

Their research indicates that mosquitoes who have developed resistance to common insecticides containing substances called pyrethroids can be killed instead with microencapsulated chlorpyrifos-methyl (CS).

Pyrethroid-based insecticides are the only ones commonly recommended for use on mosquitoes.

Dichlorodiphenyltrichloroethane, or DDT, which was used as a vector control agent around the world for several decades starting in the 1940s, is not in common use in most countries any longer. It is highly persistent in the environment and extremely dangerous to a variety of wildlife species, particularly birds.

Microencapsulation is a process by which tiny droplets are surrounded with one or more membranes. The Benin researchers used it in an attempt to increase the life-span and effectiveness of CS.

They sprayed the modified CS, a pyrethroid-based insecticide and DDT on experimental huts in the African country. The structures were located in an area prone to flooding during the rainy season.

The microencapsulated CS killed more than 90 percent of the malaria-bearing mosquitoes in the vicinity of the huts. DDT killed about 45 percent of the culicomorphs. The pyrethroid-based insecticide, a substance called lambdacyalothrin, killed about 30 percent of them.

Researchers are seeking an alternative to DDT because its toxicity has led to efforts to end its use as an insecticide. The substance is already widely banned as an agricultural pesticide, including in the United States and most developed nations.

Mosquitoes develop resistance to pyrethroid-based compounds fairly quickly. Pyrethroids are also toxic to fish and other water-borne organisms, including many species that sit at the bottom of aquatic food webs, at very low concentrations.

The authors of the study, which appears in the Feb. 8 issue of Malaria Journal, said that further research is needed to confirm their results in other areas containing mosquito species that carry malaria.

The disease, which affects as many as 500 million people every year, kills about one million humans annually. Most victims are children living in sub-Saharan Africa.