GM Mosquito Gene Spreads into Wild Populations in Brazil

THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE

 

Dear Friends and Colleagues 

GM Mosquito Gene Spreads into Wild Populations in Brazil

Scientists from Yale University have found evidence that genetically modified (GM) mosquitoes released by British biotech firm Oxitec have successfully interbred with natural populations in Brazil. This is not supposed to happen as the GM OX513A mosquitoes were designed to be ‘self limiting’ i.e., their offspring should die before reaching adulthood.

The Yale research team sampled the mosquito population in the target area in Brazil six, 12 and 27-30 months after releases commenced and concluded there was “clear evidence” that portions of the Oxitec genome had been incorporated into the natural population. 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. Three to four percent of the offspring from matings of OX513A with wild mosquitoes survived to adulthood. As a result, between 10-60 percent of the mosquitoes in the region inherited parts of the genome of the GM mosquitoes released in the trials.

In addition, the effectiveness of the GM mosquito releases, which claim to suppress mosquito populations, began to break down after about 18 months, i.e., the population which had been suppressed rebounded to nearly pre-release levels. The researchers suggest that female mosquitoes may have learned and begun avoiding mating with the GM males. Worse still, the release may have had the opposite effect and made mosquitoes even more resilient. The mosquitoes in the area are now made up of three strains mixed together: the original Brazilian locals, plus strains from Cuba and Mexico – the two strains crossed to make the GM insects. This wider gene pool may very likely make the mosquito population more robust.

“The degree of introgression is not trivial,” the scientists concluded, adding that it is not known what impacts this might have on disease control and transmission. They warned that introgression of GM genes into the next generation could introduce other relevant genes such as insecticide resistance. “These results highlight the importance of having in place a genetic monitoring program during such releases to detect unanticipated outcomes,” they stressed.

With best wishes,

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Item 1

TRANSGENIC AEDES AEGYPTI MOSQUITOES TRANSFER GENES INTO A NATURAL POPULATION

Benjamin R. Evans, Panayiota Kotsakiozi, Andre Luis Costa-da-Silva, Rafaella Sayuri Ioshino, Luiza Garziera, Michele C. Pedrosa, Aldo Malavasi, Jair F. Virginio, Margareth L. Capurro & Jeffrey R. Powell
Scientific Reports volume 9, Article number: 13047 (2019)
https://www.nature.com/articles/s41598-019-49660-6

Abstract

In an attempt to control the mosquito-borne diseases yellow fever, dengue, chikungunya, and Zika fevers, a strain of transgenically modified Aedes aegypti mosquitoes containing a dominant lethal gene has been developed by a commercial company, Oxitec Ltd. If lethality is complete, releasing this strain should only reduce population size and not affect the genetics of the target populations. Approximately 450 thousand males of this strain were released each week for 27 months in Jacobina, Bahia, Brazil. We genotyped the release strain and the target Jacobina population before releases began for >21,000 single nucleotide polymorphisms (SNPs). Genetic sampling from the target population six, 12, and 27–30 months after releases commenced provides clear evidence that portions of the transgenic strain genome have been incorporated into the target population. Evidently, rare viable hybrid offspring between the release strain and the Jacobina population are sufficiently robust to be able to reproduce in nature. The release strain was developed using a strain originally from Cuba, then outcrossed to a Mexican population. Thus, Jacobina Ae. aegypti are now a mix of three populations. It is unclear how this may affect disease transmission or affect other efforts to control these dangerous vectors. These results highlight the importance of having in place a genetic monitoring program during such releases to detect un-anticipated outcomes.

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Item 2

GENETICALLY ENGINEERED MOSQUITOES OUT OF CONTROL 

GE insects are spreading in Brazil
Wednesday, 11 September 2019
https://www.testbiotech.org/en/press-release/genetically-engineered-mosquitoes-out-of-control

According to a new scientific publication, genetically engineered mosquitoes produced by Oxitec (Intrexon) have escaped human control after trials in Brazil. They are now spreading in the environment. The yellow fever mosquitos (Aedes aegypti) are genetically engineered to make it impossible for their offspring to survive. After release they were supposed to mate with female mosquitos of the species which are transmitting infectious diseases, such as Dengue fever, to diminish the natural populations. However, the now published research shows that many offspring of the genetically engineered mosquitos actually survived and are spreading and propagating further. According to the scientists, between 10-60 percent of the mosquitoes in the region concerned are inheriting parts of the genome of the mosquitoes released in the trials. These findings are also confirmed in neighboring regions where no such trials were conducted.

The long-term consequences for the transmission of diseases, the number of insects and the interactions with the environment cannot be predicted. The mosquitoes used for the genetic manipulation are originally from Cuba and Mexico. These insects used in the laboratory have now mixed with the Brazilian insects to become a robust population which can persist in the environment over a longer period of time. They might replace the original insects on the long term and even enhance the problems associated with the mosquitoes.

“The Oxitec trials have led to a situation that is largely out of control. The company has released its patented insects although it was known before that some insects could survive in the environment. The expectations of their investors was more important than the protection of health and the environment. There is no insurance and no fast-track mechanism to prevent severe damage in a worst-case scenario,” says Christoph Then for Testbiotech. “This incident must have consequences for further applications of genetic engineering. Preventing the spread of genetically engineered organisms within natural populations has to become a priority.”

Several research institutions players are planning to create genetically engineered trees, bees, corals, several insect species and other organisms that can spread in natural populations. The long-term impacts of such trials are generally unpredictable. Unintended effects can disturb or disrupt ecosystems and lead to the extinction of species. Therefore, Testbiotech is proposing to introduce new criteria for the risk assessment of genetically engineered organisms to make sure they can be prevented from spreading uncontrolled into the environment.

Contact: 

Christoph Then, info@testbiotech.org, Tel + 49 15154638040

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Item 3

FAILED GM MOSQUITO CONTROL EXPERIMENT MAY HAVE STRENGTHENED WILD BUGS

By Michael Irving
September 12, 2019
https://newatlas.com/science/genetic-engineering-mosquito-experiment-goes-wrong/

Mosquitoes are more than just a pest – they can be downright dangerous carriers of disease. One of the most innovative ideas to control populations of the bugs has been to release genetically modified male mosquitoes that produce unviable offspring. But unfortunately a test of this in Brazil appears to have failed, with genes from the mutant mosquitoes now mixing with the native population.

The idea sounded solid. Male Aedes aegypti mosquitoes were genetically engineered to have a dominant lethal gene. When they mated with wild female mozzies, this gene would drastically cut down the number of offspring they produced, and the few that were born should be too weak to survive long.

Ultimately, this program should cut down the population of mosquitoes in an area – up to 85 percent, in some early tests. This of course means fewer bug-borne diseases, such as dengue, yellow fever, zika, and malaria, in humans. And since the offspring don’t live long enough to breed themselves, genes from the engineered bugs should stay neatly out of the gene pool of the wild population. The only visible effect should be the reduction of mosquito populations.

Unfortunately, that hasn’t been the case. Researchers from Yale University have now examined mosquitoes around the city of Jacobina, Brazil, where the largest test of this technique has taken place over the last few years. Not only did numbers bounce back up in the months after the test, but some of the native bugs, they found, had retained genes from the engineered mosquitoes.

“The claim was that genes from the release strain would not get into the general population because offspring would die,’’ says Jeffrey Powell, senior author of a study describing the discovery. “That obviously was not what happened.”

The GM mosquito strain was developed by a company called Oxitec, and it had previously been given FDA approval for these kinds of tests. In the Brazilian case, around 450,000 modified males were released in Jacobina every week for 27 months, totaling tens of millions of bugs. To keep tabs on them, the Yale team studied the genomes of both the GM strain and the wild species before the release, then again six, 12 and 27 to 30 months after the release began.

Sure enough, by the end of the test there was clear evidence that genes from the transgenic insects had been incorporated into the wild population. Although the GM mosquitoes only produce offspring about three to four percent of the time, it seems that those that are born aren’t as weak as expected. Some appear to make it to adulthood and breed themselves.

While populations did drop initially, numbers did bounce back after about 18 months. The researchers suggest that female mosquitoes may have learned and begun avoiding mating with the modified males.

Worse still, the genetic experiment may have had the opposite effect and made mosquitoes even more resilient. The bugs in the area are now made up of three strains mixed together: the original Brazilian locals, plus strains from Cuba and Mexico – the two strains crossed to make the GM insects. This wider gene pool could make the mozzies more robust as a whole.

The scientists assure the public that the mixed mosquitoes pose no extra health risk, but there is still cause for concern. It’s unclear exactly what effect this will have on disease transmission or other control methods.

“It is the unanticipated outcome that is concerning,” says Powell. “Based largely on laboratory studies, one can predict 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 research was published in the journal Scientific Reports.

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Item 4

GM MOZZIES PASS ON ALTERED GENE

Cayman News
9 Sept 2019
https://caymannewsservice.com/2019/09/gm-mozzies-altered-gene/

The genetically modified Aedes aegypti mosquitoes developed by Oxitec may have impacted the actual genetics of the natural mosquito populations where these bio engineered bugs were released, scientists have found. Following a release in Brazil, similar to the one in the Cayman Islands, researchers who monitored the release said that up to 30 months after the releases started there was clear evidence that portions of the altered gene have shown up in the target population.

In other words, the bio-bugs were reproducing and passing on the scientifically altered gene to their offspring, which were surviving. According to the theory of GM mosquitoes, this was not supposed to happen; the offspring of females that mated with the genetically modified males should not have survived, thereby cutting the population.

In the research paper published in the Scientific Reports section of Nature, the authors said rare viable hybrid offspring between the release strain and the local population were sufficiently robust to be able to reproduce.

“It is unclear how this may affect disease transmission or affect other efforts to control these dangerous vectors. These results highlight the importance of having in place a genetic monitoring program during such releases to detect un-anticipated outcomes,” the scientists said.

With traditional insecticides becoming less and less effective against the Aedes aegypti, the Cayman Islands was one of several countries which partnered with Oxitec to release their genetically manipulated male mosquitoes, which carried a fluorescent protein gene to allow detection of the offspring. Millions of mosquitoes were released in West Bay during the pilot project, which was terminated last year, but the largest such release so far was in Jacobina in Brazil.

The researchers monitored the release to determine if it impacted the genetics of the natural population. They set out from the position that if the bio-bugs were working as intended, the result would simply be a drop in mosquito numbers and the genetics of the target population would not be affected.

However, it appears that 3-4% of the offspring from matings of OX513A with wild mosquitoes have survived to adulthood, and although they are weak, scientists do not yet know if they are fertile.

“The degree of introgression is not trivial,” the scientists concluded, adding that it is not known what impacts this might have on disease control and transmission. They warned that introgression of genetically modified genes into the next generation could introduce other relevant genes such as insecticide resistance.

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