Fighting mosquito with mosquito: A GM-size bite against dengue

Experiment using mutant male Aedes aegypti that are sterile currently under way in Maharashtra, award-winning technology has been a success in Brazil.

Written by Amitabh Sinha | New Delhi | Published:August 31, 2015 3:35 am
dengue, mosquitoes, dengue-transmitting mosquitoes, Sex-switching mosquito gene, mosquito gene, mosquito, deadly dengue Last year, a total of 13 dengue cases and 109 malaria cases were reported in the city.

Should an ongoing experiment in Jalna, Maharashtra, have the same success as it has achieved in Brazil, India might be rid, to an extent at least, from disease-causing mosquito species.

And you will have mosquitoes themselves to thank — genetically-modified male mosquitoes, that is.

A little-known private company, Gangabishan Bhikulal Investment and Trading Ltd, or GBIT, is testing a British technology that is aimed at controlling populations of Aedes aegypti, the mosquito species that is responsible for transmitting dengue, chikungunya and yellow fever.

The technology, using genetically engineered male Aedes aegypti, was developed a few years ago by Professor Luke Alphey of the Department of Zoology at Oxford, who started a commercial company, Oxitec, to market his creation.

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The technology involves the alteration of the genetic composition of male mosquitoes by introducing a strain called OX513A that renders them sterile. When these male mosquitoes mate with female wild mosquitoes, the gene is passed on to the offspring, which do not survive beyond the larva stage. The only way to keep them alive is by administering an antibiotic called tetracycline, which, however, is not available in nature.

If these GM male mosquitoes are released in sufficient numbers, the mosquito population in a given area can come down drastically within a very short time. The average life span of the Aedes aegypti is only about 15 days.

The technology, which has fetched several awards for Alphey in recent years, has been successfully tested in Brazil, and authorised for commercial use. Several other countries including the United States and Panama too are carrying out testing.

GBIT, founded by B R Barwale, a Padma Bhushan awardee who also founded the better-known Maharashtra Hybrid Seeds Company Private Limted or Mahyco, has entered into a partnership with Oxitec to use this RIDL (release of insects carrying a dominant lethal gene) technology.

GBIT procured some 10,000-12,000 GM mosquitoes from Oxitec for research in September 2011. The original set has reproduced several generations of mosquitoes since then in a controlled laboratory atmosphere, thanks to tetracycline, which ensured that offspring survived.

After carrying out several laboratory experiments and obtaining regulatory permissions from the government, GBIT researchers are finally ready for controlled field trials. A small number of GM mosquitoes will be released in enclosed spaces containing female wild mosquitoes.

“The crucial thing is the efficiency with which the GM males are able to mate. In the open atmosphere, they will have to compete with normal male mosquitoes to mate with females. If there is a 50:50 chance of the females selecting the GM males, then the experiment can be considered very successful, and would mean that mosquito populations can be reduced fairly quickly,” Dr S K Dasgupta, lead scientist with GBIT, said.

The ability of GM mosquitoes to mate is only one of the criteria on which the future of the technology depends. GBIT scientists will have to demonstrate it is environmentally safe, does not impact normal living of any other species, and is not harmful for humans. Only then can it go ahead with commercialisation. The process is similar to that for any GM product, such as agricultural crops.

GBIT has been asked by the government to run an awareness campaign in nearby human habitats about the experiment, and address the concerns of residents. The controlled mating exercise will have to be repeated over several months and over several generations of mosquitoes to enable GBIT researchers to draw statistically relevant conclusions. The experiments can then be carried out in the open atmosphere.

“This technology is not only environment-friendly, but is also effective in controlling the rising health menace caused by mosquitoes,” Dasgupta said. Dengue has killed almost 1,000 people in India since 2009.

Dasgupta said the technology is not aimed at eliminating all mosquitoes — which is theoretically possible through the use of this technology, but involves larger ethical questions — but only at controlling the spread of disease. “The purpose of this technology is to control dengue and chikungunya and is species-specific to Aedes aegypti. It can be extended to other disease-bearing mosquitoes too. But the basic purpose is to eliminate the species-specific disease-carrying mosquito population,” he said.

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