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Genetically modified mosquitoes that target dengue fever and Zika released in U.S.

Mosquito larvae planted in the Florida Keys are expected to hatch tens of thousands of genetically engineered mosquitoes this week, marking the first time such insects have been released in the wild in the United States. The eggs were supplied in late April by a biotechnology company, called Oxitec, as part of a government permitted project to investigate the use of genetic engineering to decrease disease-carrying mosquito populations. The action is aimed against an invasive species known as Aedes aegypti, which spreads illnesses including Zika, dengue, chikungunya, yellow fever, and other, many of which are on the rise in Florida.

The startup used genetic engineering to modify male mosquitoes to pass on a gene that causes females to need a dose of the antibiotic tetracycline to live. Females who propagate the illness die as larvae if they don’t have it. Males, who have been altered to not bite, seek out wild females to mate with in order to pass on the fatal trait to future generations. Over time, more females die.

Insecticides are now being used to suppress this species, although they are relatively ineffective. Resistance has been seen in the field, indicating that new technologies are necessary.

“As we are seeing development of resistance to some of our current control methods, we are in need of new tools to combat this mosquito,” said Andrea Leal, executive director of the Florida Keys Mosquito Control District. “And given the unique ecosystem we live in, those tools need to be safe, environmentally friendly and targeted.”

Other countries have explored Oxitec’s method for releasing genetically engineered insects. In several of their publications, [the business] claims to have suppressed the Aedes aegypti population by more than 90%, including effective control of the Aedes aegypti population in Brazil. The trial in the Keys is anticipated to work and lower Aedes aegypti numbers, based on previous testing, and, presumably, it will have a direct epidemiological impact by lowering disease transmission effectively.

Molecular biologist, Omar Akbari, has a research group that focuses on genetic modification technology, at the University of California, San Diego. He’s also a co-founder of Agragene, a biotech firm that uses genetically altered agricultural pests to fight a variety of harmful pests. He shared his insight on the event saying, “Oxitec has received approvals to do releases of its modified A. aegypti mosquitoes in the Cayman Islands and Panama. It is doing trials in India—genetically modified mosquitoes are released into cages with wild-type mosquitoes to mate and then compared with cages without the modified insect. [Others have] donereleases in Malaysia and Australia. And as there are more examples of success stories, I think more countries will be willing to adopt this technology, assuming that the costs make sense.”

“With global warming, the habitable range of A. aegypti mosquitoes is expanding. The species now is present in many U.S. states, whereas 10 years ago it wasn’t. This, too, is going to become more important as this mosquito species becomes more prevalent and the pathogens also become more prevalent.”

A preprint study from Akbari’s lab, which is presently being reviewed, describes a new CRISPR-based method that may be used to eradicate Aedes aegypti populations. It’s also self-restrictive. “We’re excited about this because we were able to eliminate the populations in experimental cages in the lab,” he said. “And we think this technology might be a next-generation technology that can be used alongside the Oxitec technology.”

Oxitec scientists are working on eight different types of genetically altered insects, including two varieties of malaria-transmitting mosquitos, as well as worms, moths, and flies that feed on important crops. Third Security, a venture capital firm located in Radford, Va., owns the company, with initiatives backed by a combination of foundation and corporate supporters.

According to experts in the field, the mosquito is a difficult target in terms of basic biology and genetics.
Flaminia Catteruccia of the Harvard T.H. Chan School of Public Health, who helped pioneer mosquito genetic engineering, says, “They have this extraordinary resilience in their genome. What they’ve shown us over and over again is [that] if we are not very subtle and if we just try to kill them, they will find a way out.”

The field test, in a broader sense, marks a turning point in the genetic engineering of entire species of disease-carrying insects, or any other sexually reproducing animal or plant in the wild. While genetically modified crops are already ubiquitous, genetically modified insects have not yet been extensively adopted.

“It’s a landmark project, and it represents a big corporate milestone for us,” says Oxitec CEO Grey Frandsen. “I think more importantly that it’s a very big step for the field.”

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