Genetically modified mosquitoes, like those released in Grand Cayman, successfully interbred with natural populations in Brazil, according to the authors of a new study in the Nature science journal.

Researchers from Yale University found evidence that mosquitoes released by British biotech firm Oxitec had impacted the genetics of the overall mosquito population following releases in Jacobina, Brazil.

The genetically modified OX513A mosquitoes – the same strain as those released in a similar project in Grand Cayman – were designed to be ‘self limiting’. When they were introduced in Cayman, officials said the GM mosquitoes were modified so that their offspring would die before reaching adulthood.

The aim was to release millions of them into the wild so that through weight of numbers they would out-compete the resident males for mates and cause the overall mosquito population to collapse. The goal was to help eradicate diseases like Zika, dengue fever and chikungunya which are spread by the Aedes aegypti mosquitoes. The project was abandoned in Cayman earlier this year amid doubts over its effectiveness.

The Yale research team sampled the mosquito population in the target area in Brazil six, 12 and 30 months after releases commenced and concluded there was “clear evidence” that portions of the Oxitec genome had been incorporated into the natural population.

“Our data clearly show that release of the OX513A has led to significant transfer of its genome (introgression) into the natural Jacobina population of Ae. Aegypti,” the researchers wrote.

They go on to caution that such releases need more robust monitoring.

“These results highlight the importance of having in place a genetic monitoring program during such releases to detect unanticipated outcomes,” the authors wrote.

According to the research paper, hybrid offspring of the GM mosquitoes and the natural population were able to reproduce in nature, meaning the modified genome persisted even after the releases had stopped.

The authors reported between 10% and 60% of individuals had some evidence of the OX513A genome, depending on the sample and criterion used.

They said it is not known what impact that would have on disease control or transmission.

The authors did note a reduction in the prevalence of the Oxitec gene over time, suggesting the modified mosquitoes were at a “selective disadvantage” over the longer term.

They also noted that the mosquitoes did not carry any greater risk of infectivity for dengue or Zika, though they cautioned that they noted they may be more resistant to insecticide and may have contributed to a generally more genetically robust mosquito population.

Oxitec CEO Grey Frandsen said the company had not yet had time to review the paper but “looks forward to doing so soon”.

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  1. Remember also that when me and Dwene was begging the government to halt the project amidst all the uncertainty surrounding the GM mossies, the Premier alluded that I was misleading the country, that the mossies were “100% risk-free”; further, Mr Petrie said that we were not a research experiment.

    Now we can all see who was misleading the country, we can all see that there were unknown risks, we can all see that the nation was lied to that it was 100% risk free and that if not “we” at least certainly “I” was an unwilling participant in a medical research trial.

    Now, we must further consider the real implications since this revelation of their ability to transfer their gene – what really do we have on our hands (we know that we now have a mutated species)? How dangerous will these insects be in the future? They were released first at the West Bay clinic – will this remain the hotspot for them? If so, how will they affect patients/attendees there? The self-destruct gene was supposed to be a poison cocktail that included a strain of the e-Coli virus and two other viruses.

    “These results highlight the importance of having in place a genetic monitoring program during such releases to detect unanticipated outcomes,” the authors wrote.

    What other “unanticipated outcomes” will appear in the future? We don’t know but what we now know is that the people were right, the government was wrong and we have been recklessly placed in this position by the government.