Mosquitoes are not only a pest but they can be absolute dangerous carriers of many diseases. In order to control their populations, an advanced solution has been to release genetically modified male mosquitoes that produce unviable offsprings. However, unluckily, an experiment in this area seems to have been unsuccessful in Brazil, with genes from mutant mosquitoes now integrating with the local population.
What Was The Initial Plan?
The concept appeared to be ideal. Male Aedes aegypti mosquitoes were genetically engineered to have a leading lethal gene. When they coupled with wild female mozzies, this gene would significantly reduce the number of offspring they produced, and the little that were born should be too unhealthy to live for long.
Eventually, this plan should minimise the population of mosquitoes in an area – estimated up to 85 percent, in some initial tests. Thus, resulting in lesser bug-borne diseases, such as malaria, yellow fever, dengue, and zika in humans. Meanwhile the young don’t persist long enough to reproduce themselves, DNAs from the engineered bugs should stay carefully out of the gene group of the wild population. The only noticeable effect should be the decline of mosquito populations.
Did It Work?
Regrettably, that hasn’t been the case. Researchers from Yale University have now scrutinized mosquitoes around the city of Jacobina, Brazil, where the primary test of this technique has taken place over the past few years. It was not only the numbers that have raised in the past few months but the native bugs were found with retained genes from the engineered mosquitoes.
A senior writer of the study, Jeffery Powell said that it was expected that the genes from the release strain would not diffuse in the general population as the offspring would die, but things did not go as planned.
A company known as Oxitec developed the GM mosquito strain and it had been formerly given FDA consent for these types of experiments. In the Brazilian situation, around 450,000 genetically modified mosquito males were freed in Jacobina every week for 27 months, adding up tens of millions of bugs. To keep a track on them, the Yale group studied the genomes of both the wild species and the GM strain before the release, then again six, 12 and 27 to 30 months after the release commenced.
At the end of the experiment, there was enough evidence that genes from the transgenic insects had been assimilated into the wild population. Even though the GM mosquitoes only reproduce three to four per cent of the time, the ones that are born are not as feeble as anticipated. Many appear to reach adulthood and reproduce themselves.
While populations did reduce in the beginning, numbers did spring back after about 18 months. The scientists put forward that female mosquitoes may have learned and started escaping coupling with the altered males.
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Even worse, the genetic experiment may have had the reverse effect and made mosquitoes even more resistant. The insects in the area are now comprised of three strains mixed together: the original Brazilian locals, plus strains from Mexico and Cuba – the two strains cross over to make the GM insects. This broader gene pool could turn the mozzies more robust as a whole.
“It is the unexpected outcome that is alarming,” says Powell. “Founded largely on laboratory studies, one can forecast what the likely outcome of the release of transgenic mosquitoes will be, but genetic studies of the sort we did should be done during and after such releases to determine if something different from the predicted occurred.”
The researchers convince the public that the mixed mosquitoes show no additional health risk, but there is still a source for worry. It’s uncertain exactly what effect this will have on disease spread or other control procedures.
The research paper was printed in the journal Scientific Reports.