Mosquito-specific pesticide in the offing?

By Archita Bhatta
Published: Wednesday 28 February 2007

-- is another menacing insecticide ready for a run? Scientists from Rochester University's Mayo Clinic in the us claim to have made a breakthrough in creating a pesticide that can kill mosquitoes without affecting people.

The Rochester researchers have identified two specific amino acid residues in the enzyme acetylcholinesterase (ache) that are present in the anopheles mosquito, which spreads malaria. Published online in the December 26 issue of Public Library of Science, the study claims that a newly designed pesticide can target the two specific amino acid residues. Since these residues are absent in many mammals including humans, the pesticide will spare them.

Will this development affect the rest of the food chain and the development of resistance to such pesticides? K Gunashekaran, deputy director of the Vector Control and Research Centre (vcrc), Pondicherry, says: "The study has shown that the two amino acid residues are absent in the ache of mammals. However, they are present in other structural and functional proteins. How the new insecticide will affect these sites is difficult to predict." P K Saha, director, vcrc, feels that this could be a move to launch a new product under the garb of safety.

Yuan Ping Pang, the lead author, says that the research will pave way for an advanced, innovative and species-specific pesticide. The new pesticide will be designed to alleviate the resistance problem by targeting the two unique residues, he adds.

But Gunashekaran says the new study may not directly lead to a fifth, safer generation pesticides. Mosquitoes develop resistance to organophosphorous pesticides through ache mutation. Hence, only a new class of insecticides can interact with the mutated ache as a whole so that mammalian toxicity can be minimised. Most pesticides work by crippling the serine residue--another amino acid of the enzyme ache. This serine residue is present in both insects and mammals and, therefore, any pesticide targeting this amino acid affects both insects and mammals. ddt is one such pesticide.

The jury is firmly out on whether the Mayo clinic study will provide an alternative.

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