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Scientists arming new weapon against dengue, malaria — mosquitoes

Phase 2 of trials underway in Jalna on ‘friendly’ mosquitoes genetically modified to cause offspring to die. Next step? Limited tests in open field

Written by Kavitha Iyer | Jalna |
Updated: July 3, 2017 9:17:16 am
malaria mosquitoes, Aedes Aegypti, dengue, malaria, monsoon season diseases, india news GBIT got around 12,000 male OX513A mosquitoes in 2011, several generations have evolved in its Jalna lab.

EVEN as urban local bodies gear up for annual monsoon outbreaks of dengue and malaria, inside a nondescript mesh cage at Jalna in central Maharashtra, trials are underway on several generations of a “friendly” mosquito that a handful of countries are already experimenting with for vector control programmes.

In the cage are hundreds of Aedes Aegypti vector mosquitoes, responsible for spreading dengue and chikungunya among other diseases, but engineered through advanced biotechnology to be self-limiting — in other words, genetically modified to cause offspring to die.

While GM Mustard continues to await a final nod from the Union government, Gangabishan Bhikulal Investment and Trading Limited (GBIT), which is testing the transgenic mosquitoes along with Oxitec Limited, an Oxford University spin-out biotech company, is pinning its hopes on the urgency around finding effective vector management technologies.

The Aedes Aegypti mosquito, the vector responsible for dengue and chikungunya outbreaks, has survived traditional fumigating and there is no immediate mass-scale programme to control these outbreaks. “From a public health perspective, this is a crucial area where intervention can be made,” says Shirish Barwale, director of GBIT, one of the Barwale Group companies that include hybrid seed major Mahyco.

GBIT got around 12,000 male OX513A mosquitoes in 2011, several generations have evolved in its Jalna lab. Nirmal Harindran

Already, Oxitec is partnering with agencies in Brazil, Panama, the US and the Cayman Islands for trials and pilot projects. In India, GBIT expects to approach regulators seeking permissions for the next phase — limited trials in an open field — early next year. ”Phase One of the trials was in the laboratory, and Phase Two, a contained trial in cages, is currently underway. Once the results of this phase are ready, then we expect to go into Phase Three, which would be open field trials,” said Dr Shaibal Dasgupta, GBIT’s lead scientist on the project. “By February or March 2018, we will be more or less ready and will submit results.”

Indian Council of Medical Research (ICMR) director Dr Soumya Swaminathan agrees that there is a need for a “graded response” to trials around GM technology meant for disease control. “We definitely need to look for alternative technologies for the future,” she said.

The “friendly Aedes” has already been trademarked by Oxitec. These are transgenic male mosquitoes with a self-limiting gene inserted through advanced genetics. Banking upon the male’s natural instinct to mate with a wild female, the OX513A strain is inherited by offspring, causing the larvae to die before maturing into adult mosquitoes.

Since GBIT brought in over 10,000-12,000 male OX513A mosquitoes from Oxitec in September 2011, several generations have evolved in its Jalna laboratory and cage, with larvae successfully maturing into adults only with doses of tetracycline added into the water where the larvae grow. GBIT scientists say batches of larvae treated with tetracycline survive, mate and produce offspring, some of which are again maintained with a dose of tetracycline.

“What we do is a regular quality check on the effectivity of the gene. We mate the OX513A male mosquito with the local female and check the mortality. That is the test of effectivity of the gene,” says Dr Dasgupta. GBIT says their quality checks have shown no deviation from the expected performance of the gene in subsequent generations of the mosquito. At Oxitec, over 150 generations of the mosquito have been tested by now, only batches getting tetracycline surviving into adulthood. Again, no deviation has been found in gene penetrance.

Asked whether the local agricultural community around the Jalna facility is aware of the active test site, GBIT says they have a detailed engagement plan to set into motion before open trials. “We would need to involve the local community for the next round of open trials, as and when we get approvals. At present, discussion with the village close to the site is on and is at the initial stages,” said an official of GBIT.

Among the things they expect to tell villagers is that only male mosquitoes are to be released — the male Aedes Aegypti neither bites humans nor spreads disease. Also, the OX513A gene being self limiting, it does not remain in the environment unless it gets tetracycline. Scientists also say no toxins are introduced in the bio-engineered OX513A mosquitoes, so birds eating these mosquitoes will not be in any danger. Also, as the Aedes Aegypti only mates with its own kind, DNA sequences will not be spread to any other organism.

But one problem, is the absence of convincing data from previous trials on the impact of a reduced vector population on incidence of disease. Other doubts include the possibility that the wild female will, over generations, prefer only the wild male Aedes Aegypti.

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