The insects are said to fight diseases such as dengue fever and West Nile
Photo illustration, source: Joao Paulo Burini / Getty Images
Reengineering Life is a series by OneZero about the amazing way in which genetic engineering is changing humanity and the world around us.
in the As the first test of its kind in the US, millions of genetically modified mosquitoes will be released in the Florida Keys over the next two years.
Local officials shed light on the plan in a 4-1 vote August 18th, despite longstanding objections from some residents and environmental groups. The constructed insects are designed to wipe out Aedes aegypti mosquitoes in order to eradicate the diseases they transmit. The British company Oxitec, which makes the mosquitoes, had tried to get a release for the past 10 years.
The resulting offspring do not survive to adulthood and therefore cannot reproduce.
The U.S. Environmental Protection Agency approved the pilot in May, followed by the state of Florida in June. However, Oxitec still had to get a local permit before the mosquitoes could be released at a location in Monroe County, home of the Florida Keys.
The male mosquitoes from Oxitec are constructed in such a way that they have a “self-limiting” gene. When released into the wild and mate with females, they pass the gene on to their offspring. The resulting offspring do not survive to adulthood and therefore cannot reproduce. Oxitec believes that the release of enough of these designer insects will cause the local mosquito population to eventually die off.
Male mosquitoes don’t bite – only women – so according to the EPA and Oxitec, the artificial mosquitoes pose no threat to humans. However, opponents are concerned about the potential health and environmental effects of the release of genetically modified organisms into the environment.
Climate change is expected to bring more diseases such as dengue and West Nile, which are transmitted by the bite of infected mosquitoes. Florida currently uses airplanes to spray large amounts of insecticides to control mosquitoes, but the chemicals only kill about 30% to 50% of the local Aedes aegypti population and the effectiveness may wear off over time. The Florida study tests how effective the Oxitec approach is in eliminating the pests.
Amid the ongoing coronavirus pandemic, the Florida Department of Health has confirmed 47 cases of dengue fever and 44 cases of West Nile virus so far this year. Both are spread by the bite of female Aedes aegypti mosquitoes. The dengue cases are all clustered in Monroe County, where the genetically modified mosquitoes are released. The field test will take place sometime in 2021 or 2022, but the exact time and date has yet to be determined.
Dengue fever often presents as a severe flu-like illness that can be accompanied by severe muscle aches and pains, fever, and sometimes a rash. Symptoms appear within 14 days of being bitten by an infected mosquito. However, most people infected with West Nile virus never get symptoms. When they do this, they may experience a headache, body ache, joint pain, vomiting, or diarrhea.
Over the past ten years, Oxitec has tested its mosquitoes in Malaysia, Brazil, Panama and the Cayman Islands. In a recent field test in the Brazilian city of Indaiatuba, the company claimed its mosquitoes were 95% effective in reducing local mosquito populations compared to untreated control posts in the same city.
In a study published in Scientific Reports in September 2019, a group of independent scientists found that some offspring of Oxitec’s genetically engineered mosquitoes survived and produced their own offspring. The paper raised concerns that the company’s technology could create hybrid wild mosquitoes that worsen the spread of diseases they are designed to prevent. Oxitec denied the claims and in March the magazine published an addendum to the original paper.
When Wolbachia-carrying males mate with wild females, the bacteria prevent the resulting offspring from hatching.
Oxitec’s technology is one of several approaches that are being investigated to eliminate pathogenic mosquitoes. Truly, the life science division of Google’s parent company Alphabet is also working on its own mosquito control technique. In recent years, Verily has released millions of laboratory-bred male Aedes aegypti mosquitoes in several neighborhoods of California’s Central Valley in hopes of reducing their numbers. An infection with dengue or West Nile virus is unusual there due to the dry climate. However, if the approach works, it can be used in other locations where mosquito-borne diseases are a greater threat.
Truly, mosquitoes are not genetically modified. Rather, they are bred to carry a common insect bacterium called wolbachia, which prevents them from reproducing. When Wolbachia-bearing males mate with wild females, the bacteria prevent the resulting offspring from hatching.
Oxitec has already carried out field trials with its genetically modified diamond moths at Cornell University in New York. These moths are engineered to share the same self-limiting gene as the mosquitoes. Wild diamond moths feed on crops like cabbage, broccoli, cauliflower, and canola, and cost farmers an estimated $ 4 to 5 billion each year.
Oxitec’s proposal to test its genetically modified mosquitoes in Florida met with considerable opposition. A petition against the release of the mosquitoes has garnered almost 240,000 signatures. Critics say the mosquitoes could harm Florida’s ecosystem, although an EPA risk assessment found Oxitec technology poses no risk to humans, animals, or the environment, including endangered species.
Last week’s Florida vote could open the door to designer mosquitos in other parts of the US. In May, the EPA also approved a field test in Harris County, Texas, where Houston is located. No state or local approval has yet been granted there.
“There are currently no agreements or plans to move the project forward,” a Harris County Public Health spokesman told CNN. “Our focus is on our efforts against the Covid-19 pandemic.”