Thursday, March 17, 2016

Genetically Modified Mosquito Field Test

On Monday, the Food and Drug Administration (FDA) released for public comment a draft Environmental Assessment (EA) submitted by Oxitec, Ltd., that assesses the potential environmental impacts of a field trial of the company’s genetically engineered (GE) Aedes aegypti mosquitoes (OX513A) in Key Haven, Florida. Aedes aegypti is known to transmit human viral diseases, including Zika, dengue, yellow fever and chikungunya and is an invasive species of mosquito that has taken of residence in Florida and parts of the south.

After a long period of review, last week the FDA announced a preliminary finding that there would be no significant impact on the environment (FONSI) if Oxitec and Key Haven, Florida proceeded with a field trial of Oxitec’s genetically engineered mosquito in the Florida Keys after a public comment period and a review of the public comments. According to the FDA announcement, the preliminary FONSI is based on FDA’s review of the draft Environmental Assessment and other data, observations made by FDA inspectors and CDC expert during an inspection of the company site, and a visit to the proposed field study site. The FDA worked with the U.S. Environmental Protection Agency (EPA) and the Center for Disease Control and Prevention (CDC) to review the application by Oxitec.

Aedes aegypti mosquitoes are a non-native species in the USA. They can spread serious diseases such as dengue fever and chikungunya and are a known carrier of Zika. Dengue fever and chikungunya are currently not an active health threat in the Florida Keys because the Florida Keys Mosquito Control District has been working hard to reduce the Aedes aegypti population, but spraying of mosquitos has only limited success in controlling the population.

Using advanced genetics and molecular biology Oxitec has developed a genetically modified mosquito, Aedes aegypti 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. After an Oxitec mosquito has successfully mated with a wild female, any offspring that result will not survive to adulthood, so the mosquito population declines.

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 predetermined and sustained period of time. Open field trials of the OX513A genetically engineered mosquito have been conducted in Brazil, the Cayman Islands, Panama, and Malaysia.

OX513A mosquitoes have been genetically 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 offspring of mating between OX513A males and wild-type females. The fluorescent marker is used to identify the genetically modified mosquitos.

The plan is Oxitec to produce genetically modified mosquito eggs in Oxford, UK and ship them to Marathon, FL for rearing and ultimately release in the proposed field trial. The goals of the proposed investigational trial are to evaluate the breeding of the OX513A mosquitoes with local wild-type Aedes aegypti females, to assess the survival of their offspring, and to estimate the suppression of the overall Aedes aegypti population at the trial site relative to an untreated comparison area. At the conclusion of the investigational field trial, the OX513A mosquitoes would die off at the end of their natural lifetimes in the environment (approximately two days) and wild-type Aedes aegypti levels are expected to recover to pre-trial numbers.

To submit your comments electronically to the docket, go to and type FDA-2014-N-2235 in the search box. The Environmental Assessment can be read at this link and the FDA finding of no significant impact here.

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