Furore over first GM mosquito trial

• Project could open door for new era of gene-tweaking for pest control, disease prevention
• Critics fear for possible negative impact on health, environment
• Three vaccines offer complete protection against Zika virus in monkeys

Scientists have made major breakthroughs in their quest to eliminate mosquito-borne diseases by deploying genetically modified version of the vector and three new vaccines.

For the first time, the United States Food and Drug Administration (F.D.A.) has approved the trial of free-flying genetically modified (G.M.) mosquitoes even as three vaccines have offered complete protection against Zika virus in monkeys.

It is believed that the near global outbreak of Zika virus could open door for new era of gene-tweaking for pest control and disease prevention.

But critics urge for caution following unpleasant consequences reported with the use of GM crops.

According to the World Health Organisation (WHO), mosquitoes are one of the deadliest animals in the world. Their ability to carry and spread disease to humans causes millions of deaths every year. In 2015, malaria alone caused 438 000 deaths. The worldwide incidence of dengue has risen 30-fold in the past 30 years, and more countries are reporting their first outbreaks of the disease.

Zika, dengue, chikungunya, and yellow fever are all transmitted to humans by the Aedes aegypti mosquito. More than half of the world’s population live in areas where this mosquito species is present. Sustained mosquito control efforts are important to prevent outbreaks from these diseases.

There are several different types of mosquitoes and some have the ability to carry many different diseases. Other mosquito-borne diseases include: West Nile virus, filariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, Eastern equine encephalitis, Venezuelan equine encephalitis, and La Crosse encephalitis.

Until now, the WHO recognises GM mosquitoes as possible tools for fighting the spread of mosquito-borne Zika virus, Dengue fever and malaria.

But the FDA decision, announced August 5, 2016, and published in Science News, covers only a specific, preliminary test release of GM mosquitoes on Key Haven in the Florida Keys, where no locally transmitted Zika cases have been reported.

Last year, researchers at the University of California, U.S., reported that inserting a modified gene into mosquitoes makes them incapable of carrying the malaria parasite.

Not only did the mosquitoes in the study become malaria-resistant, but they were able to pass the gene to 99.5 per cent of their offspring. That means that within a few generations, they could spread the gene to wild mosquitoes, effectively creating a natural barrier to malarial infection.

Meanwhile, the FDA ruled that the planned trial of OX513A mosquitoes, genetically engineered by the British company Oxitec, “would be unlikely to result in adverse effects on the environment or human health.”

Oxitec uses advanced genetics to insert a self-limiting gene into its mosquitoes. The gene is passed on to the insect’s offspring, so when male Oxitec engineered mosquitoes are released into the wild and mate with wild females, their offspring inherit the self-limiting trait. The resulting offspring will die before reaching adulthood, and the local mosquito population will decline.

Indeed, if U.S. commissioners approve it, the trial would release abundant GM male Aedes aegypti species carrying a gene that will cause their offspring to die.

Also, known as the yellow fever mosquito, Aedes aegypti, is a mosquito that can spread dengue fever, chikungunya, Zika fever and yellow fever viruses, and other diseases. The mosquito can be recognized by white markings on its legs and a marking in the form of a lyre on the upper surface of the thorax. The mosquito originated in Africa, but is now found in tropical and subtropical regions throughout the world.

In 2010, Oxford scientists with Oxitec genetically engineered OX513A, a sterile male Aedes aegypti mosquito with a gene that causes its larvae to die.

According to Science News, in tests in Brazil, Panama and the Cayman Islands, months of releasing these mosquitoes have reduced the wild populations of mosquitoes by 90 per cent or more. As a result, a Brazil neighborhood has seen mosquito-borne dengue cases plummet.