Killing older mosquitoes could help control malaria better

April 7th, 2009 - 4:25 pm ICT by IANS  

Washington, April 7 (IANS) Scientists have suggested that killing older mosquitoes would be a more sustainable way of controlling malaria, opening the way to insecticides that could never become obsolete.
Every year malaria kills a million people globally, but many of the chemicals used to kill mosquitoes become ineffective as repeated exposure breeds a new generation of mosquitoes resistant to that insecticide.

“Insecticides sprayed on house walls or bed nets are some of the most successful ways of controlling malaria,” said Andrew Read, professor of biology and entomology, Penn State University (PSU).

“But they work by killing the insects or denying them the human blood they turn into eggs. This imposes an enormous selection in favour of insecticide-resistant mosquitoes.”

Read and his colleagues - Matthew Thomas, professor of entomology at PSU and Penelope Lynch, doctoral student at Open University - argue that insecticides that kill only older mosquitoes are a more sustainable way to fight the deadly disease, said a PSU release.

“It is one of the great ironies of malaria,” explained Read, “Most mosquitoes do not live long enough to transmit the disease. To stop malaria, we only need to kill the old mosquitoes.”

Since most mosquitoes die before they become dangerous, late-acting insecticides will not have much impact on breeding, so there is much less pressure for the mosquitoes to evolve resistance, explained Read, who is also associated with the PSU Centre for Infectious Disease Dynamics.

“We are working on a fungal pesticide that kills mosquitoes late in life,” said Thomas.

“We could spray it onto walls or onto treated materials such as bed nets, from where the mosquito would get infected by the fungal spores.”

These findings appeared in the Tuesday edition of PLoS Biology.

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