Monday, September 21, 2020

Genetically Modified Mosquitoes to be released in Florida

In August the Florida Keys Mosquito Control District (Mosquito Control District) Board of Commissioners voted to allow the release of Oxitec’s Genetically Modified Aedes aegypti mosquitoes in 2021. This comes after a decade of study, focus groups and regulatory approvals for the project by the U.S. Environmental Protection Agency (EPA), the U.S. Centers for Disease Control and Prevention (CDC), and seven State of Florida agencies, including the Department of Health. A petition against the project had more than 25,000 signatures according to Science News.

This project will be overseen by Mosquito Control District, the EPA and the Florida Department of Agriculture and Consumer Services (Department of Agriculture). Independent evaluation of the project will be provided by the U.S. CDC, the University of Florida, the Department of Health, and local leaders.

Aedes aegypti mosquitoes are a non-native species in the United States. They can spread serious diseases such as dengue fever and chikungunya and are a known carrier of Zika. The Florida Keys Mosquito Control District has been working hard to reduce the Aedes aegypti population to control dengue fever and chikungunya, but spraying of mosquitos has only limited success in controlling the population. There were in August 47 cases of dengue fever that were locally acquired.

Using advanced genetics and molecular biology Oxitec has developed a genetically modified Aedes aegypti mosquito that is designed to control the Aedes aegypti mosquito population. Oxitec has used genetic modification to create male insects which seek out and mate with females. Male mosquitoes do not feed on blood (bite). After an Oxitec mosquito has successfully mated with a wild female, any female offspring that result will not survive to adulthood, and the male offspring will survive to become fully functional adults with the same genetic modification, providing multi-generational effectiveness that could ultimately lead to a reduction in Aedes aegypti mosquito populations in the release areas.

This approach is targeted at a single species, unlike conventional insecticides or pesticides which kill insects indiscriminately. According to the company, this is more effective and is much better for the environment than pesticide spraying. In the field trial the Oxitec modified mosquitoes will be released and monitored in an area of the Florida Keys over a year. Open field trials of the Oxitec genetically engineered mosquito have been conducted in Brazil, the Cayman Islands, Panama, and Malaysia. EPA anticipates that this could be an effective tool to combat the spread of certain mosquito-borne diseases in light of growing resistance to current insecticides. This will be the first release of any genetically modified mosquitoes in the United States.

The genetically modified mosquitoes have been engineered to encode a conditional or repressible lethality trait, which is a function of the overexpression of the tetracycline-repressible transactivator (tTAV) protein, and a red fluorescent marker protein. When tetracycline is not present, tTAV causes lethality in the female offspring of mating between genetically modified males and wild-type females. The fluorescent marker is used to identify the genetically modified mosquitos. In addition, according to Oxitec, the genetically modified mosquitoes are susceptible to pyrethroid pesticides which many Florida Keys Aedes aegypti mosquitos no longer are susceptible to. The field test will exclude areas where tetracycline may be openly available.

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