Monday, October 31, 2011

The release of genetically modified mosquitoes in nature might prevent disease

A field trial has revealed that genetically modified organisms released in nature are able to, or at least partly, integrate with the native population. In a recent study, male mosquitoes that can carry the dengue virus were genetically altered to render them unable to survive without antibiotics. The arthropods were kept alive in the lab, whereafter they were released in nature, where they managed to mate with females and produce offspring, carrying the same genetic difference that causes them to die before mature age when left untreated. This shows releasing modified organisms into the wild can help us in reducing the numbers of disease carriers.The idea is to let as much modified males mate with females, leaving less wildtype males able to procreate, thus effectively reducing the numbers of mosquitoes because their offspring dies before maturation. In the field trial, mosquitoes of the strain A. aegypti were modified, which is the carrier of the deadly dengue virus. Because there is no proper treatment for dengue, reducing the numbers of the species that carries the disease and brings it to humans provides an alternative strategy to combat the virus. 
A. aegypti
The trials revealed that the genetically altered versions are able to mate with normal females, consequently producing fertilized eggs. This is the first trial where a genetically altered version mated with the normal population: experiments with releasing genetically altered organisms into nature have been tried before, but the lab versions were not successful enough. They were beaten by their wildtype counterparts and were thus unable to reproduce.

Being able to release modified mosquitoes into the wild to reduce the production of viable offspring is also relevant for malaria, the most prevalent parasitic disease worldwide, that still kills almost 800.000 people each year. The disease is caused by a parasite that resides, just like dengue virus, in mosquitoes, that can consequently be transferred to humans. Developing the same method for malaria appears to be harder though, because the parasite can live in several mosquito species, while dengue virus is restricted to just A. aegypti.

Not every researcher is happy with the development of these techniques to eradicate a mosquito population. Some scientists argue unexpected consequences of genetic modification could result in the formation of a 'super strain' of mosquitoes, that might have undesirable properties as a side-effect, possibly being even more harmful to humans than their wildtype counterpart. Therefore, when creating a genetically modified organism, scientists will need to take a lot of time to properly assess the risks of the newly created mosquito version. 

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