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GMO Mosquitoes to Control the Spread of Disease Carries Unknown Risks

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GMO Mosquitoes to Control the Spread of Disease Carries Unknown Risks
Biologist releases GMO mosquitoes in Piracicaba, Brazil on Feb. 11, 2016. Victor Moriyama / Getty Images

By Natalie Kofler, Françoise Baylis, Graham Dellaire, Landon J Getz

Every year, around one million people die of mosquito-borne diseases according to the World Health Organization (WHO). This is why mosquitoes are considered one of the deadliest living creatures on the planet — not because they are lethal themselves, but because many of the viruses and parasites they transmit are.


Consider, for example, dengue fever. This mosquito-borne virus is a leading cause of hospitalization and death among children and adults in several countries in Asia and Latin America. In 2016, member states in three of the six WHO regions reported 3.34 million cases.

In the absence of an effective vaccine for dengue fever, Zika fever, chikungunya and other mosquito-borne diseases, researchers have developed genetic strategies to reduce mosquito populations. One such strategy involves the release into the wild of genetically modified (GM) mosquitoes that express a lethal gene — a strategy believed to have little impact on the overall DNA of wild populations of mosquitoes.

As an interdisciplinary group of authors, we generally support technologies that can reduce human disease and suffering. However, given our combined expertise in science, governance and ethics we have concerns that recent decisions to deploy GM mosquitoes have not been made responsibly.

Genetically Modified Mosquitoes

The transfer of new genes from GM organisms to wild or domesticated non-GM populations is a key criticism of GM crops like soybean and corn. There are concerns that the introduction of GM genes into non-target species could have negative consequences for both human and environmental health.

Oxitec, a company that spun out of research at Oxford University in the early 2000s, developed and trademarked GM Friendly™ mosquitoes (also known as strain OX513A of Aedes aegypti). These male GM mosquitoes have what the company describes as a "self-limiting" gene, which means that when these so-called friendly mosquitoes mate, their offspring inherit the self-limiting gene which is supposed to prevent them surviving into adulthood.

In theory, when these mosquitoes are released in high numbers, a dramatic reduction in the mosquito population should follow.

Changes to the Gene Pool

According to research published by Oxitec researchers in 2015, field trials involving recurring releases of Friendly™ mosquitoes demonstrated a reduction of nearly 95 percent of target populations in Brazil. In these field trials, experiments were not performed to assess whether GM mosquitoes might persist in the wild.

A recent study from the Powell lab at Yale University has since confirmed that some of the offspring of the GM mosquitoes didn't succumb to the self-limiting lethal gene and survived to adulthood. They were able to breed with native mosquitoes and thereby introduce some of their genes into the wild population.

The Yale researchers found that mosquitoes captured at six, 12 and up to 30 months post-release carried DNA from the GM mosquito population, thereby disproving "the claim that genes from the release strain would not get into the general population because offspring would die."

It appears that between five and 60 percent of the captured mosquitoes post-release contained genetic sequences inherited from the Friendly™ mosquitoes. Importantly, the number of mosquitoes identified as still containing DNA derived from GM mosquitoes declined between the 12-month and 27-month capture periods specifically, perhaps indicating that the offspring of GM mosquitoes might be less fit in nature after all. This remains to be shown conclusively.

Unknown Potential Impacts

Meanwhile, the impact of mosquitoes carrying these new genes remains largely unknown. One significant worry is that a new breed of mosquito might emerge that is more difficult to control. These new genes could also potentially alter evolutionary pressures on viruses carried by mosquitoes, like dengue fever, in unpredictable ways. This includes potentially increasing their virulence or changing their host-insect interactions. These are hypothetical risks that have been raised by scientists, and reflect the need for further study.

Thus, like GM soybean or corn, there is legitimate concern about the propagation of new genetic material in wild populations with as yet unknown consequences.

Field trials involving the release of GM organisms are typically designed to evaluate safety and efficacy, to assess possible impact on food networks, and to ensure that there is no (or minimal) undue harm to the environment or human health. Put simply, field trials are meant to assess potential harms associated with genetic technologies and to provide opportunities to minimize these harms before moving forward with more large-scale releases.

This raises two important questions: Given that "around 5 percent or less" of the GM mosquito population was expected to survive, shouldn't Oxitec have made plans to assess the risk of gene transfer to wild populations during their initial trials? And shouldn't the Brazilian government have required such an assessment as part of the regulatory approval process, given their awareness of the risk?

Instead, with approval from Brazilian authorities, Oxitec released nearly half a million GM mosquitoes every week into shared environments in Jacobina over a two-year period from 2013 to 2015. This was done without the benefit of adequate risk assessment and without proper public consultation.

Oxitec reports having used leaflets, social media, carnival parades and community meetings to inform the public of their research. Public education is not the same as public consultation and engagement and, in our view, the people living in the vicinity of this release had more than a right to be informed of the plans. They also had a right to participate in relevant decision-making.

On the basis of presumed success in Brazil where mosquito populations were reduced — a consequential reduction in the prevalence of dengue fever has yet to be demonstrated — plans have been made to extend field trials to other jurisdictions, including the Florida Keys in the U.S.

To date, public pushback has temporarily prevented the release of GM mosquitoes in the Florida Keys. But Oxitec hopes to eventually secure approval from the U.S. Environmental Protection Agency to perform field trials and assess release of a second-generation GM mosquito that causes lethality only in female mosquitoes, as another means to collapse wild populations.

Regulating Genetic Modification

In the end, minus the hyperbole and somewhat alarmist reporting of the Yale study (the journal is looking into allegations brought forth by Oxitec of speculative and unsubstantiated claims), the finding that offspring of GM mosquitoes could survive in the wild remains undisputed. This illustrates the importance of careful decision-making and adequate oversight of field trials involving the release of GM organisms. Careful decision-making requires open venues for informed and deliberative public dialogue, engagement and empowerment.

Genetic modification technologies need to be more transparent, as do the scientific processes for evaluating their risks, especially where the rights and needs of affected communities can inform technology development. With more robust and nuanced regulatory processes governing the development and release of GM organisms, it should be possible to benefit from these technologies without harming or disenfranchising the communities that are the intended beneficiaries.

Mosquito-borne illnesses cause immense human suffering, and we should continue to develop technologies to reduce that suffering. At the same time, we must be equally dedicated to designing scientific processes that are safe, ethical and just.

Reposted with permission from our media associate The Conversation.

A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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