A small village of 3,000 people in northeastern Brazil is playing a possibly seminal role in the history of global health. Trials that hold the possibility of saving thousands of lives from extreme morbidity and mortality are currently being conducted there. Just as significantly, the trials are highly controversial, and are likely to reignite the perma-smoldering debate about genetically modified organisms.
Mandacaru, an isolated village of 3,000 in the state of Pernambuco, Brazil, has served as host to one of the first trials of genetically-modified mosquitoes in the wild, and the initial results are in: The indigenous A aegypti mosquito population fell precipitously, by 96%. It’s likely that as a result hundreds of Brazilian lives were spared the pain and mortality resulting from dengue fever.
Oxitec, the British biotechnology company that created the process of modifying mosquitoes, said in a press release that “The result is a major success, and shows an even greater level of effectiveness for Oxitec’s approach than that demonstrated in previous evaluations in Brazil and the Cayman Islands.” Part of the success is due to Mandacaru’s isolation, which allowed continual releases of modified mosquitoes to snuff out the indigenous population.
Here’s a simplified version of how the process works: Oxitec inserts two genes into lab-grown A aegypti mosquito eggs. One’s a marker to track the modified mosquitoes, the other a “time-bomb” gene that triggers the lethal over-manufacture of a protein that interferes with new cell formation. Millions of mosquitoes are then bred before the females are killed and the males are released into the wild, and they quickly mate with indigenous A aegypti females, passing along the inserted genes. Within days — before the female’s larvae grow enough to begin looking for a human blood meal — the mosquitoes die. Modified mosquitoes are released every few weeks, and slowly begin to take over the population, which means that, over time, the number of blood-hungry mosquitoes falls.
A aegypti mosquitoes are the primary vector for dengue fever, a viral disease that causes excruciating pain (it’s also known as “breakbone fever”). The implications for severely decreasing dengue — or even wiping it out entirely — are massive. Estimates on the incidence of dengue infection vary, but 50 million to 390 million people are infected each year, causing about 25,000 deaths. There is no cure and treatment is palliative, consisting of fluids, painkillers, and blood transfusions for those who suffer from a severe case. Research on a dengue vaccine is ongoing, so preventing transmission involves mosquito control strategies — spraying pesticides, eliminating standing water sources, and similar measures.
The approach pioneered by Oxitec isn’t without its critics, as recent articles in the New Yorker and Mother Jones outlined. Like crops and other organisms under the broad genetically-modified organism (GMO) umbrella, the debate is about fear of the “unknown unknowns.” For example, in 2010, a Deloitte survey found that more than a third of Americans were extremely concerned or very concerned about GMO food, despite the reigning scientific consensus that GMO foods are no different than conventional foods.
Many are wary of the unintended consequences of genetically modified mosquitoes, noting that no one knows the long-term repercussions on the fauna of mosquito-less areas, or what the potential human consequences could be.
Even those who are more sanguine on the use of genetically modified mosquitoes in general are wary of over-reliance on one for-profit organization specifically. A geographic area would be reliant on Oxitec’s mosquitoes, which require continual releases at regular intervals. Currently, the technique is only useful in isolated areas, and scaling it would require modified mosquitoes to be released in multiple areas simultaneously, a potential coordination issue for interested countries.
It's clear that the debate won't be finished anytime soon. In the meantime, more trials will be undertaken, and more research will be conducted to attempt to better understand the long-term ramifications of introducing genetically-modified mosquitoes.