QUESTION

Is it possible to breed mosquitoes in the laboratory and then sterilize them and release them into the environment in order to reduce their rate of reproducing.

ANSWER

That is a very good question, and indeed efforts to genetically modify mosquitoes in order to control the various diseases they transmit are underway in many laboratories across the world.

For almost 15 years, scientists have had the ability to modify mosquitoes so that they are sterile. The aim, as you rightly describe, is then to release these sterile mosquitoes into the wild in order to reduce numbers. If the gene that causes sterility can be passed to future offspring, without any reduction in survival of the insect, then the eventual result will be a total population extinction.

To date, many of the major mosquito disease vector species have been successfully genetically modified, though there are many fewer instances of field testing of these modified insects. For example, in 2000/2001, a World Health Organisation-led project in India created sterile mosquitoes of one species of each of the three main disease vector genera: Culex, Aedes and Anopheles, the latter of which acts as vectors for malaria. However, the project did not, in the end, release any of the modified Anopheles vectors into the wild.

While many scientists applaud the benefits of this approach (such as being very species-specific and being more environmentally friendly than spraying), there are also causes for caution. For example, there are concerns that the loss of mosquitoes in the food chain will have a negative impact on animals that rely on them for food. Similarly, if mosquitoes vanish from an ecosystem, their “niche” may be filled by another organism that is equally or even more dangerous and destructive, such as a crop pest or another disease vector. There is also a worry that changing mosquitoes may have unexpected and dangerous effects on the disease itself, for example forcing it to evolve into a more severe disease or changing its epidemiological patterns in ways we cannot predict in advance.

Finally, not all scientists are convinced that the approach will work in the first place—the sterile mosquitoes will have to survive equally well or better than normal mosquitoes in order to establish in the population, and must be equally or more successful at reproducing. As such, while a lot of money is being poured into GM mosquitoes, it is still the center of vigorous debate.

Perhaps the best indication of this controversy came last year, when Oxitec, a British company, released sterile Aedes aegypti mosquitoes on the Cayman Islands. These mosquitoes are the vectors of dengue fever, and so all eyes are on this study to see whether indeed sterile mosquitoes can survive in a population, and if they do, what other effects they will have longer term on the population size of mosquitoes and the rest of the ecosystem. You can read more information about that here: Oxitec: GM Mosquito Factory.