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Scientists in The Gambia Target Mosquito Larvae in Fight Against Malaria

Malaria is rampant in sub-Saharan Africa, and effective control of the disease is being threatened by growing drug resistance in the malaria parasite and insecticide resistance in malaria-transmitting mosquitoes.

In The Gambia, researchers supported by NIAID are testing an alternate strategy for malaria control: the use of larvicides that kill larvae of Anopheles gambiae, the mosquito responsible for spreading the disease.

 

Mosquito larvae in standing water.
Larva of an Anopheles mosquito in standing water
According to the researchers, larval control, while historically successful, has been largely neglected over the years. The goal of this study is to determine if widespread use of microbial larvicides (i.e., those based on bacteria that produce larvae-killing toxins) will suppress the development of adult mosquitoes to such an extent that the prevalence and transmission of malaria in local communities will also decline.

 

To test their hypothesis, the researchers are assessing the effectiveness and impact on transmission of two microbial larvicides: Bacillus thuringiensis var.israelensis (Bti) and B. sphaericus (Bs). Both larvicides are desirable because they specifically target mosquito larvae and do not appear to elicit resistance.

Researchers established four study sites along the River Gambia covering roughly 100 square kilometers each. During the rainy season (July to November), the river rises and floods wide areas, resulting in intense transmission of malaria and an increase in clinical cases of the disease.

So far, the researchers have been able to identify the sources of malaria mosquitoes in each of the four study areas and establish the most effective strategy for killing larvae using Bti and Bs, including the best combination of the two larvicides and the most efficient length of time before re-treatments. They have also developed a method for large-scale application in the study areas.

The latest results from this study show that the use of microbial larvicides in The Gambia significantly reduced the abundance of anopheline mosquitoes in natural habitats. More results are expected from this study after data from the 2007 field trial are analyzed.

See the associated article in Malaria Journal .

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Last Updated March 26, 2008