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Tuesday, June 1, 2021

genetically modified mosquitoes !!


கவுண்டமணி காமெடி முழங்கிக்கொண்டு இருந்த நாட்களில் –

இந்த கொசுத்தொல்லை தாங்க  முடியலையப்பா ! என்பது பிரபல வாசகம்.


There are some names which are associated with bad things and ‘Aedes’ is perhaps one – derived out of Greek aedes, meaning "unpleasant" or "odious". The all important red coloured body fluid which supplies oxygen to tissues gets affected by Aedes – coagulation, a complex process by which blood forms clots gets affected. Aedes is a genus of mosquito originally found in tropical and subtropical zones, but now found on all continents excluding Antarctica.  The feared fever ‘dengue’ is linked to - Aedes aegypti, a mosquito.  The mosquitoes are a family of small, midge-like flies: the Culicidae. Although a few species are harmless or even useful to humanity, most are considered a nuisance because they consume blood from living vertebrates, including humans.  When half-asleep, a pierce to one’s skin, leaving behind an itchy red welt and possibly even a serious illness.

There was a time when ‘mambalam mosquitoes’ were famous (there was a Cricket team too in that name !)  – now you have them in every area -  be it – Triplicane, Mylapore, Medavakkam, Madipakkam, Parrys, Velachery  – name any area – most popular myths have been exploded – they are found on every floor of very tall structures too.  A few  decades ago, all houses in Triplicane [and other areas like Mylapore, Mambalam, Saidapet] had wells ~ to prevent breeding of mosquitoes, Corporation officials would visit houses and drop some quantity of pesticide in the well. Guppies were bred in temple tanks and other ponds – Corporation official would visit home with an  earthen pond having hundreds of fish – and he would drop a handful of them into the well [everytime, we would take few of them and grow them in Horlicks bottles ! – their tails were attractive].

Male mosquitoes do not bite. The real risk is from female mosquitoes that search for blood to provide protein for their eggs. Scientific research over the years has shown that female mosquitoes find their prey using a combination of sensory cues including light, shape, colour, heat, vibration, sweat and other by-products of human activity.

Read an interesting article in Live Science that first genetically modified mosquitoes were released in US.   It reported that the  biotech firm Oxitec has released its genetically modified mosquitoes in the Florida Keys, with the goal of suppressing wild, disease-carrying mosquito populations in the region. This is the first time genetically modified mosquitoes have been released in the U.S. 

Oxitec previously released its modified Aedes aegypti mosquitoes in Brazil, the Cayman Islands, Panama and Malaysia, and the company reported that local A. aegypti populations fell by at least 90% in those locations, Live Science previously reported. A. aegypti can carry diseases such as Zika, dengue, chikungunya and yellow fever, and releasing modified mosquitoes offers a way to control the population without using pesticides.  Oxitec's modified mosquitoes, all male, have been engineered to carry a lethal gene; when the modified pests mate with wild female mosquitoes, the lethal gene gets passed on to their offspring. Though the gene does not affect the males' survival, it prevents female offspring from building an essential protein and thus causes them to die before reaching maturity.  (sounds a lot cruel and against the nature – but mankind is known for all these – killing everything else in their own interests !)

Only female mosquitoes bite people (male mosquitoes exclusively drink nectar), so the modified mosquitoes and their surviving male offspring can't pass diseases to humans. A. aegypti mosquitoes make up about 4% of the mosquitoes in the Florida Keys but cause the vast majority of mosquito-borne disease transmitted to humans in the area, Nature reported. The Florida Keys Mosquito Control District (FKMCD) board typically budgets $1 million a year to control the pest, resorting to costly measures such as spraying aerial insecticides, according to Gizmodo.  Releasing hundreds of millions of genetically modified mosquitoes may be a less expensive and more effective option, the board concluded, especially as mosquito populations become resistant to pesticides over time.

FKMCD first approached Oxitec in 2010, and after a decade of regulatory assessments and local pushback, both the board and the U.S. Environmental Protection Agency (EPA) finally approved the plan to release the genetically modified mosquitoes in the Keys, according to Nature. In late April, the company placed boxes of mosquito eggs at six locations in Cudjoe Key, Ramrod Key and Vaca Key, according to Nature. Over the next 12 weeks, about 12,000 newly hatched male mosquitoes should emerge from the boxes.  This release will serve as an initial trial so that Oxitec can collect data before running a second trial with nearly 20 million mosquitoes later this year, Nature reported. The company will capture mosquitoes throughout the trial to observe how far the insects travel from their boxes, how long they live and whether female mosquitoes are actually picking up the lethal gene and dying off. To make it easier to track the modified mosquitoes, Oxitec introduced a gene that causes the mosquitoes to glow under a specific color of light.

The trial faces strong opposition from a small subset of Florida Keys residents, as well as the Center for Food Safety and the Florida Keys Environmental Coalition, Live Science previously reported. Concerned that the egg boxes might be vandalized, Oxitec placed them on private property and did not disclose their exact locations to the public, Nature reported. 

Questions remain about whether the genetically modified mosquitoes will have unintended effects on local mosquitoes, animals or the ecosystem at large, Live Science previously reported.  For instance, after Oxitec released genetically modified mosquitoes in Jacobina, Brazil, genes from the insects cropped up in local mosquito populations, hinting that the lethal gene failed to kill off some female offspring before they could mate. Their hybrid offspring did not carry the lethal gene, but instead carried genes from the original Cuban and Mexican mosquito populations first used to create the genetically modified mosquitoes, according to a 2019 study published in the journal Scientific Reports. It's unclear whether or how these new genes might have altered the mosquitoes' biology.

The mosquito in Enthiran that would bite Aishwarya Rai ~ after which Robo Rajini would run, find it in a slum, catch and present it – was named ‘Ranguski’ – perhaps the nickname of my favourite writer Sujatha, whose story was filmed by Shankar.

With regards – S. Sampathkumar


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