GM mosquitoes ready to kill their old 'deadly' cousins

In India where every second death is caused by a mosquito bite, this route promises some respite, though it sounds a trifle bizarre. An innovation-led British company Oxitec is developing genetically modified mosquitoes to be released in the country with its India investment arm.

These genetically modified organisms (GMOs) are expected to reduce the rate of vector-borne diseases in India such as dengue and chikungunya.

Chikungunya and dengue are both transmitted by mosquitoes or 'Aedes aegypti', as they are called scientifically. While successful trials are done in Cayman Island, Brazil and Panama, no trials were carried in India so far. Till date, more than 100 million Oxitec mosquitoes have been released worldwide.

"No releases of any kind have taken place yet in India, though lab-based studies have been underway in India by our development partner, Gangabishan Bhikulal Investment and Trading Ltd (GBIT), since 2011," Kevin Gorman, senior field operations manager at Oxitec told dna in an email statement, adding a location for a pilot study will be identified and confirmed during the regulatory process.

"The first steps of a pilot study would then be held to begin a programme of local and wider community engagement, with releases following in approximately 12 months," Gorman added.

The company has applied to the regulatory body, Review Committee on Genetic Manipulation (RCGM) in the department of biotechnology, for a pilot study in India. “The timeline for the regulatory process is not defined as such; it is up to the independent experts reviewing the application to determine when they are fully satisfied that it can go ahead. There would be no releases until that happens,” he said.

The result of the trial it carried out in Juazeiro city, northeast Brazil, the Oxitec mosquito successfully controlled the Aedes aegypti mosquito by reducing the target population by 95%. "In every trial, the Oxitec mosquito has shown greater than 90% reduction of the dengue mosquito," Gorman confirmed.

But, how this would help? Oxitec mosquitoes are genetically engineered, so their offspring die before they can reproduce and before they can become transmitters of disease. And there is a "colour marker" gene for monitoring the results.

"It's an approach similar to the Sterile Insect Technique (SIT) where male insects are sterilised by radiation and released to mate with pest females. With successive releases there are fewer offspring and the pest population crashes," the response read.

The Oxford-based biotech company releases virtually all males. "We sort the males from the females as pupae and have a greater than 99% sorting efficiency. But inevitably we will release a few females but this is negligible. In a recent trial in Panama the pest Aedes aegypti population was reduced by over 90%," Gorman further said.

He also confirmed that the Oxitec mosquitoes are no different to wild mosquitoes except they cannot reproduce effectively and have a colour marker to identify them. "The insects die and their offspring die and the mosquitoes and their genes do not persist in the environment," the spokesperson said.

However, there have been some arguments by the environmental groups which said the genetically-engineered insects would have a wide range of impact on environmental and human health, such as new diseases may fill the environment or there could be some horizontal transfer of these "genes" into other species. It was also said that in presence of tetracycline (a broad-spectrum antibiotic), which is now available in the environment, these genetcally modified mosquitoes can survive.

However, Oxitec in its response said, "Studies and scientific literature have shown that the level of tetracycline found in the environment is not high enough to function as an antidote to the self-limiting gene. Tetracycline degrades rapidly under outdoor conditions including UV radiation. Also Aedes aegypti mosquitoes reproduce in clean pools of water. The only difference between our mosquitoes and the ones you already have is that ours have a colour marker to identify them and they cannot reproduce effectively."