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Sunday 24th June 2018

New dengue control method

20th July 2009

A research team in the Peruvian Amazon has found a way to get adult mosquitoes which carry dengue fever to carry pesticide back to their young and kill them.


When the adult Aedes aegypti mosquitoes carried the insecticide back to their own breeding sites, most of the larvae there were killed.

Aedes aegypti mosquitoes breed in stagnant water, where they lay eggs and larvae develop. Repeated treatment of breeding sites is costly and time-consuming, however.

Adult mosquitoes 'commute' between breeding grounds and resting place, a trait which the research team exploited.

They disseminated a safe and persistent insecticide, pyriproxyfen, in areas used as resting grounds by adult mosquitoes, which are neither killed nor repelled by it.

The adults then carried the pesticide back to breeding grounds, ensuring a strong, wide coverage of aquatic breeding grounds. Because adult mosquitoes move around so much, the scheme proved highly efficient at killing most of the larvae in breeding grounds.

Mosquitoes that develop in small, hidden habitats in urban areas which are difficult to get to or discover are particularly suited to this control method.

The team sprayed insecticide in just 3-5% of adult resting areas at two sites in a public cemetery in Iquitos, Peru.

They found that the effect was lethal, with 95–100% death rates among larvae developing in nearby breeding grounds, compared with an average mortality of 7–8% in uncontaminated sites.

Only tiny quantities of pyriproxyfen are required to achieve this effect, minimising environmental impact. The insecticide also sterilises adult female mosquitoes and decreases male sperm production.

Researchers said health department personnel would need to inspect and treat houses every week, or set resting traps for mosquitoes that were already laden with the pesticide.

Experts said the technique could also be useful for the control of other mosquito-borne diseases.

Any species with predictable resting or feeding sites and breeds in relatively small aquatic habitats would be a potential target.

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