The bite that can wait

The Department of Biotechnology (DBT) is reportedly hesitant about giving permission for field trials to release genetically modified (GM) mosquitoes to tackle the menace of diseases such as Zika, dengue and chikungunya. The concept to reduce the population of Aedes aegypti mosquito, which is the carrier of these diseases, is sound in theory. However, DBT scientists fear — rightly — that there may be unknown hazards associated with doing this on scale. 

The initiative comes from the Mumbai-based company, Gangabishan Bhikulal Investment and Trading Limited (GBIT), which is promoted by the Barwale family that also controls Maharashtra Hybrid Seeds Company (Mahyco). GBIT wants to introduce a new GM male Aedes aegypti mosquito. This GM insect has been bred by Oxitec, an R&D biotech company with roots in the University of Oxford. Diseases such as Zika, dengue and chikungunya are transmitted when an infected, pregnant female mosquito bites somebody. Males don’t bite and are, therefore, harmless. Oxitec has bio-engineered a transgenic male Aedes aegypti mosquito, which carries a new gene fatal only to female mosquitoes.

The idea is to release a large number of such GM male mosquitoes into the trial zone. These will then breed with normal females in the wild. In the next generation, only the males would survive and these would breed again, with normal females. After a few generations, the female population will be drastically reduced and eventually this cycle will result in a reduction of the entire mosquito population.

Since the life cycle of a mosquito is only around two-three weeks, the effects of the trial should be apparent in a few months. Transgenic males don’t bite and the specific modified genes are said to be harmless to humans. In fact, the so-called “Friendly Aedes” project launched “closed cage” trials in January 2017 at the Oxitec facility in Jalna, Maharashtra. Trials have been launched in Malaysia, Brazil, and Florida as well. Permission has now been sought for open field trials in India.

The DBT's fears are based on the fact that open field trials could result in unknown consequences to the environment, or ecology. The Aedes aegypti is part of the food chain. During its life cycle, it is consumed by fishes, during its early aquatic phase by frogs and then by birds, lizards and spiders. A drastic reduction in the mosquito population could impact prey species, resulting in ecological collapse. There is also the admittedly less likely possibility that the engineered genes could directly harm various species that consume mosquitoes. 

In a broader sense, Indian policy has been very cautious about allowing the introduction of genetically modified technologies. Only GM cotton seeds are permitted in the agro sphere and GM mosquitoes would be an entirely new area of GM technology. Controlling mosquito population is obviously a key concern, given the harm caused globally by malaria, Zika, dengue and chikungunya. It's estimated that close to 700 million people are infected each year, and over a million die. Given globalisation, these insects and the diseases they carry have been transmitted all over the world. Traditional methods of control such as insecticide sprays are harmful to the environment as well as humans.

GM mosquitoes have been bred in many trials around the world. New methods of gene-editing such as CRISPR enable precise bio-engineering. Apart from population reduction, there have also been attempts to create transgenic mosquitoes, which cannot carry these deadly viruses. Genes captured from the fruit fly, for example, can be bred into mosquitoes, which are rendered incapable of carrying deadly diseases. This approach has been tried in various countries including Australia, Brazil, Indonesia, Mexico. While the technology certainly holds promise in tackling endemic diseases, the DBT's concerns are legitimate. More research may be required, including the study of data from other field trials, to ensure that there are no unforeseen consequences.