'Dead End' Mosquitos

A controversial plan by U.K. biotechnology firm Oxitec could eliminate a virus that causes 2.3 million infections and 25,000 deaths per year worldwide, but at the expense of driving an entire species to extinction.

Oxitec scientists have engineered flightless female and sterile male Aedes aegypti mosquitoes that either cannot reproduce or whose offspring die before reaching maturity.

“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,” according to the company’s website. “By applying the Oxitec Control Programme to an area, the mosquito population in that area can be dramatically reduced or eliminated.”

Their goal is to stop the transmission of dengue fever, which according to the World Health Organization, has spread rapidly in recent decades, putting nearly half of the world’s population at risk for infection. It is spread from person to person almost exclusively by Aedes aegypti.

Dengue typically causes flu-like symptoms and joint pain, but can rarely develop into dengue hemorrhagic fever, or severe dengue, which causes tissue bleeding and sometimes death.

As of now, there is no cure—or even a specific treatment—for dengue. All affected populations can do is spray insecticide and erect nets to keep the mosquitoes at bay.

Oxitec’s genetically modified organisms, or GMOs, may seem like the perfect solution—kill them before they kill us—but public reaction to the mosquitoes has been decidedly mixed.  

As with genetically modified food crops, many worry about the unknown consequences of disrupting natural ecosystems and playing favorites with living things.

Not in My Backyard: Controversial Testing

Oxitec is no stranger to controversy. In 2009, the company quietly released 19,000 of the “dead end” mosquitoes on Grand Cayman Island in the Caribbean, followed by a larger release of around three million mosquitoes in 2010.

Other researchers—and many Grand Cayman residents—didn’t find out about the release for more than a year because Oxitec left public outreach in the hands of local authorities.

However, Oxitec reports that the Grand Cayman trials were a “complete success,” eliminating 80 percent of mosquitoes in their target area for three months.

Though scientists are divided on the impact eliminating the mosquitoes entirely would have on local ecosystems, if mosquitoes suddenly disappeared the fish and birds that feed on them could be left in the lurch.

The effect on fragile ecosystems was just one objection angry Floridians raised last summer when Oxitec proposed releasing their modified mosquitoes in the Florida Keys, where a dengue outbreak was reported in 2009.

Key West resident Mila de Mier drafted a petition to stop the Oxitec release that received more than 120,000 signatures. In the end, the mosquitoes were not set loose in Florida.

“Why would we not expect GM (genetically modified) insects, especially those that bite humans, to have similar unintended negative consequences [to GM crops]?” Mier wrote. “Will the more virulent Asian tiger mosquito that also carries dengue fill the void left by reductions in A. aegypti? Will the dengue virus mutate (think antibiotic resistant MRSA) and become even more dangerous? There are more questions than answers and we need more testing to be done.”

Oxitec’s genetic modifications aren’t foolproof. According to their own analyses, Oxitec mosquitoes are somewhat less successful breeders than their natural brethren, and a small percentage of the resulting offspring do survive to adulthood.

Government officials and some environmentalists say that the GM critters are cheaper and safer than widespread, indiscriminate spraying of pesticides in urban communities, but the public remains divided. Meanwhile, Oxitec continues to perfect and deploy its GMOs.

Full Speed Ahead for Oxitec

Oxitec has since conducted mosquito release field tests in Malaysia and Brazil, and in February, Oxitec got the go-ahead from the Brazilian government to expand their trial in the town of Jacobina. Last year, the company says they were able to eliminate 85 percent of dengue-carrying mosquitoes in a nearby suburb.

Oxitec executives were also invited to speak at the U.S. State Department conference “Biotechnology: Role of Biotechnology in Advancing Health and Food Security” in January. In a follow up, Dr. Jack Bobo, Senior Advisor for Biotechnology at the U.S. State Department visited Oxitec to discuss how the company can help the U.S. government in its efforts to eliminate agricultural pests, in addition to those that harbor disease.

Soon, GM insects may become as commonplace as GM crops, in the U.S. and around the world.

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