Way found to target yellow fever mosquitoes: study

July 8th, 2008 - 1:51 pm ICT by IANS  


Washington, July 8 (IANS) Chemicals released by water-borne bacteria tell mosquitoes where to breed, says a study that contends this discovery will help battle the mosquito menace. Scientists say these chemicals act as triggers for yellow fever mosquitoes, prompting them to lay eggs in pools or outdoor containers from where they are released.

The findings, by researchers from the North Carolina State University, will help design lures and traps to control yellow fever mosquito populations in equatorial locations and prevent or minimise the outbreak of dengue and yellow fever,

Yellow fever mosquitoes prefer water containers with just the right amounts of specific fatty acids associated with bacteria involved in the degradation of leaves and other organic matter in water, said the study’s co-authors Charles Apperson and Coby Schal.

The chemicals associated with the microbial stew are far more stimulating to discerning female mosquitoes than plain water or filtered water.

The researchers presented female mosquitoes with different types of bacteria and bacterial extracts and, in Schal’s words, figured out “what turned the mosquitoes on” to lay their eggs.

“Some water-filled containers were rejected by the female mosquito,” Apperson said.

“If we filtered the bacteria out, the mosquitoes wanted no part of the water container. But put the filtered bacteria back in the water container, and the mosquitoes would be stimulated to lay eggs.”

Female mosquitoes are choosy when it comes to finding the proper egg-laying habitats. They do not normally lay all their eggs in one location, but instead seem to distribute eggs in multiple water-filled containers.

Going a step ahead, the researchers exposed the mosquitoes to varied concentrations of the chemical brew.

High concentrations of the brew gave the mosquitoes pause, causing them to withhold their eggs. Lower concentrations were more convincing to mosquitoes, but still not as convincing as the proper amount - just 10 nanograms in 30 mm of water.

Stimulating females to lay eggs in water containers that have lethal chemicals or insect growth regulators could be another tool in the overall strategy kit to control mosquitoes - and dreaded diseases like dengue fever.

The findings of the study have been published in the latest issue of the Proceedings of the National Academy of Sciences.

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