MSNBC / AP
By MARIA CHENG
Mutant mosquitoes fight dengue in Cayman Islands
Scientists have released genetically modified mosquitoes in an experiment to fight dengue fever in the Cayman Islands, British experts said Thursday.
It is the first time genetically altered mosquitoes have been set loose in the wild, after years of laboratory experiments and hypothetical calculations. But while scientists believe the trial could lead to a breakthrough in stopping the disease, critics argue the mutant mosquitoes might wreak havoc on the environment.
“This test in the Cayman Islands could be a big step forward,” said Andrew Read, a professor of biology and entomology at Pennsylvania State University, who was not involved in the project. “Anything that could selectively remove insects transmitting really nasty diseases would be very helpful,” he said.
Researchers at Oxitec Limited, an Oxford-based company, created sterile male mosquitoes by manipulating the insects’ DNA. Scientists in the Cayman Islands released 3 million mutant male mosquitoes to mate with wild female mosquitoes of the same species. That meant they wouldn’t be able to produce any offspring, which would lower the population. Only female mosquitoes bite humans and spread diseases.
From May to October, scientists released batches of genetically mutated male mosquitoes in cages three times a week in a 40-acre (16-hectare) area. By August, mosquito numbers in that region dropped by 80 percent compared with a neighboring area where no sterile male mosquitoes were released.
For years, scientists have been working to create mutant mosquitoes to fight diseases like malaria and dengue, which they say could stop outbreaks before they start. But, others suspect it could be an environmental nightmare.
“If we remove an insect like the mosquito from the ecosystem, we don’t know what the impact will be,” said Pete Riley, campaign director of GM Freeze, a British non-profit group that opposes genetic modification.
He said mosquito larvae might be food for other species, which could starve if the larvae disappear. Or taking out adult mosquito predators might open up a slot for other insect species to slide in, potentially introducing new diseases.
Humans have a patchy track record of interfering with natural ecosystems, Riley said. In the past, such interventions have led to the overpopulation of species including rabbits and deer. “Nature often does just fine controlling its problems until we come along and blunder into it.”
Yeya Toure, who leads the World Health Organization’s team on Innovative Vector Control Interventions, called the Cayman Islands trial promising and said it’s worth continuing the genetic modification experiments.