What do we know about experiments with transgenic mosquitoes released to fight disease?

Preliminary data from the first outdoor trial in the United States are positive and suggest that the goal of killing mosquitoes capable of carrying viruses such as chikungunya, dengue, Zika and yellow fever can be achieved.

Preliminary data from the first outdoor experiment, aimed at reducing the problem of mosquitoes carrying dangerous diseases such as chikungunya, dengue, Zika and yellow fever, are positive. The biotechnology company Oxitec, which has developed insects and released about five million mosquitoes, said the news. Aedes aegypti designed in the Florida Keys, a chain of tropical islands that stretches near the southern tip of the U.S. state of Florida, where scientists have almost completed tracking release sites.

Oxitec, based in Abingdon, UK, reported the initial results of the test at a webinar on April 6, although it has not yet released full details. The experiment, launched last year, was used to test a method to suppress these dangerous insects in real conditions, having already been tested in the field in Brazil, Panama, the Cayman Islands and Malaysia.

As mentioned, wild mosquitoes A. aegypti they can carry viruses such as chikungunya, dengue fever, zika and yellow fever, so scientists have long been looking for ways to reduce these populations. Oxitec, in particular, has developed males from A. aegypti carrier of a lethal gene for female offspring, with the ultimate goal of killing the wild population of potentially virus-carrying mosquitoes. In other words, once released into the environment, the modified males would have to mate with wild females, passing the lethal gene to the females who would have to die before they could reproduce. When more women died, the population of A. aegypti therefore it should decrease.

The experience in the USA

To make sure the mosquitoes follow this pattern, the researchers placed boxes of Oxitec mosquito eggs on some private property in the Florida Keys and surrounded them with traps, which covered a radius of more than 400 meters. Some traps, the researchers said, served as egg-laying sites while others caught adult mosquitoes.

Artificial, non-biting males mated with the wild population, and wild females laid their eggs in Oxitec traps, as well as elsewhere, such as pots, litter bins, and soda cans. In all, the researchers collected more than 22,000 eggs from the traps and took them to their lab to hatch for observation.

Oxitec reported that all women who inherited the lethal gene died before reaching adulthood. ” The researchers were able to determine if the gene was inherited because the mosquitoes that carry it fluoresce under a certain light. – explains an article about Nature -. In addition, the team found that the killer gene persisted in the wild population for two to three months, or about three generations of mosquito offspring, and then became extinct.“.

No mosquitoes have been identified carrying the lethal gene outside the 400-meter radius of the release point, even after several generations. Oxitec monitored the release sites for ten weeks after the discovery of the last mosquito carrying the lethal gene. ” I like how they know doing the experiment said Thomas Scott, an entomologist at the University of California involved in the research. They do the test in a systematic and thoughtful way, although they still have a lot of work to do“.

This pilot study was not intended to determine the effectiveness with which the method can kill the wild population, so additional testing will be needed to see if it is possible to control potentially virus-carrying wild populations with this technique. Oxitec plans to collect this data through an extension study in the Florida Keys, but to do so it must first be approved again by state regulators. The company also plans to release artificial mosquitoes at a second study site in Visalia, California, where it is currently building a research and development facility.

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