GOOD­BYE MALARIA?

Amid global protests, sci­en­tists find a new way to con­trol malaria by mod­i­fy­ing mos­quito sperm to pro­duce only male off­spring

Down to Earth - - CONTENTS - KUN­DAN PANDEY

Sci­en­tists can now mod­ify mos­quito sperm to pro­duce only male off­springs

THE THOUGHT of the world be­ing rid of mosquitoes is enough to give many a good night’s sleep. The idea is close to be­ing a pos­si­bil­ity. Sci­en­tists from Im­pe­rial Col­lege, Lon­don, have suc­cess­fully demon­strated a ge­netic vec­tor con­trol strat­egy that wiped out most of the fe­male mosquitoes in a cage. The ex­per­i­ment was part of a re­search on deal­ing with malaria, a vec­tor-borne dis­ease spread by the bite of fe­male mosquitoes.

In June, their re­search pa­per, pub­lished in the jour­nal Na­ture Com­mu­ni­ca­tion, es­tab­lished that wip­ing out mosquitoes by ster­ile in­sect tech­nique is pos­si­ble. In the ex­per­i­ment, sci­en­tists in­serted a dna-cut­ting en­zyme, called I-PpoI, into the Anophe­les gam­biae mos­quito, the most ef­fi­cient malaria vec­tor known. In nor­mal re­pro­duc­tion, half of the sperms bear the X chro­mo­some and pro­duce fe­male off­spring, and the other half bear the Y chro­mo­some and pro­duce male off­spring. The en­zyme that the re­searchers used en­sured that al­most no sperm car­ried the fe­male chro­mo­some.As a re­sult, the off­spring of the ge­net­i­cally mod­i­fied (GM) mos­quito was al­most ex­clu­sively male.

The mosquitoes were tested in a lab and it was found that the method cre­ated a fer­tile mos­quito strain that pro­duced 95 per cent of male off­spring. This is the first time sci­en­tists were able to ma­nip­u­late the sex ra­tio of mosquitoes. It took the re­searchers six years to pro­duce an effective vari­ant of the en­zyme.

Niko­lai Wind­bich­ler, lead re­searcher from the depart­ment of life sciences at Im­pe­rial Col­lege, says, “What is most promis­ing about our re­sults is that they are self-sus­tain­ing. Once mod­i­fied mosquitoes are in­tro­duced, males will start to pro­duce mainly sons, and their sons will do the same, so es­sen­tially they carry out the work for us.”

The re­sult has gen­er­ated hope as mor­bid­ity and mor­tal­ity from vec­tor-borne dis­eases have posed sig­nif­i­cant chal­lenges to public health. Ac­cord­ing to the World Health Or­ga­ni­za­tion (who), vec­tor-borne dis­eases ac­count for 17 per cent of the global bur­den of all in­fec­tious dis­eases.The most deadly vec­tor-borne dis­ease, malaria, caused 627,000 deaths in 2012.Dengue—the fastest grow­ing vec­tor-borne dis­ease in the world— has seen a 30-fold in­crease in in­ci­dence over the last 50 years.

AJIT BA­JAJ / CSE

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