In the latest attempt to stem the spread of the mosquito-borne Zika virus, scientists are now planning to release millions of mosquitoes infected with bacteria in areas of Brazil and Colombia.
The mosquitoes will be injected with Wolbachia, a naturally occurring bacteria common in insects that hampers the mosquitoes’ ability to transmit Zika to humans. The $18 million dollar project, which aims to start in early 2017, is funded by the Bill & Melinda Gates Foundation and other international donors.
Some headlines have considered the approach “far out” or “unusual,” but the tactic has been used on the Aedes aegypti mosquito for years.
Scott L. O’Neill, a professor at Monash University in Australia, came up with the idea of harnessing Wolbachia more than a decade ago with the aim of stemming the transmission of dengue fever. With a grant from the Gates Foundation in 2003, he launched a program now called Eliminate Dengue that ultimately paved the way for initial trials in northern Australia, where the microbe effectively stemmed the spread of dengue. Similar experiments have already started in Vietnam, Indonesia and Brazil, according to the New York Times.
If the current approach works as well as it has in past trials, it could be cheaper and more effective than using insecticides to reduce the risk of Zika, according to Steve Kern, the deputy director of quantitative sciences at the Gates Foundation, in an interview with the Seattle Times.
U.S. CDC map of all countries with active Zika virus transmission as of September 2016. (Creative Commons)
Still, injecting bacteria into mosquitoes is just the latest in a series of international efforts to stop the Aedes aegypti mosquito from transmitting Zika. The U.S. and other governments have allocated millions toward vaccine trials, mosquito nets and bug sprays this year, and Brazil is one of several countries to use massive quantities of insecticides to kill off mosquitoes in localized areas.
The British firm Oxitec also genetically modifies mosquitoes so that when they mate with mosquitoes in the wild, their offspring die before they can mature and breed. Researchers have already run trials in which mosquito populations and, in some cases, dengue transmission fell by 90 percent in just a matter of months.
Oxitec has proposed a field trial in the Florida Keys, which the Food and Drug Administration approved in August, and a trial is already under way in Piracicaba, Brazil.
Experts say the world is far from gaining control of the Aedes aegyti mosquito, however, which is found across Latin America, the southern U.S. and regions of Africa and Asia. According to the director of the Centers for Disease Control and Prevention, there is not yet a way to contain the spread of mosquito-borne infections, and methods to control mosquito populations are still urgently needed.
“Zika and other diseases spread by [the Aedes aegypti mosquito]are really not controllable with current technologies,” said Thomas Frieden of the CDC. “We will see this become endemic in the hemisphere.”
