Over the protests of environmental groups and NGOs, Malaysia has released 6,000 genetically engineered mosquitoes into the wild, hoping to drive down incidents of mosquito-borne dengue fever. It’s the first experiment of its kind in Asia, but naturally everyone isn’t thrilled with the idea of releasing altered DNA into the ecosystem.
Dengue fever is a particularly nasty bug found in tropical and subtropical climes like Malaysia’s, causing nausea, muscle and joint pain, fever, headaches, rashes, and sometimes death if left untreated (in Malaysia it killed 134 people last year). The experimental mosquitoes, all male, were engineered to produce offspring that quickly die in hopes that shortening life spans will thin the population of Aedes species (dengue fever is carried by females).
The experiment was conducted less to see if the GM mosquitoes’ offspring would die off earlier and more to see how the 6,000 mosquitoes themselves would fare in the wild. That also happens to be the sticking point for environmental groups and locals who are incensed that the Malaysian government went ahead with the experiment over their protests. Tweaking genomes, critics say, could lead to unforeseen and uncontrollable consequences (like causing the diseases to become more virulent).
So how did the genetically modified Aedes males fare? We don’t know yet, as the results are still being analyzed. If it turns out they were able to mingle with their unmodified cousins without generating any adverse consequences it would be huge for advocates of this kind of gene tinkering. Mosquitoes bear all kinds of illness all over the world—most notoriously malaria—and making adjustments to mosquito genomes has long been proposed as a potential solution.
As carriers for other diseases as well such as yellow fever, mosquitoes are among the deadliest creatures on the planet, responsible for millions of human deaths every year. And as the planet warms, the insects are broadly expanding their turf and bringing their diseases with them; thousands of cases of dengue, a tropical disease, have appeared in the U.S. in the past five years. DDT was long used to control the mosquito population, but it is now widely banned, and in any case, many scientists believe that mosquitoes quickly build up a resistance to the insecticide. That, in part, is why the battle against mosquitoes has gone genetic.
Generally speaking, the goal of gene-based mosquito-control projects is either to kill the insects or make them benign. Researchers at Johns Hopkins University, for example, are studying mosquitoes that were made malaria-resistant through the activation of a gene responsible for a protein that blocks the infection. And the British company Oxitec has engineered a strain of mosquito that cannot survive without regular doses of tetracycline; in the wild, these mosquitoes would survive just long enough to mate and pass on their tetracycline-junkie genes to their doomed offspring. In a trial in the Cayman Islands last year, Oxitec-modified mosquitoes were able to cut the overall population by 80 percent in just six months.
But the problem is that we don’t fully understand how mosquitoes and the diseases they carry would adapt in response to such experiments. New strains of malaria and other diseases could emerge. Jo Lines, a malaria expert at the London School of Hygiene and Tropical Medicine has described the process as “a series of arms races that the [malaria] parasite has consistently won.” Three percent of the offspring from Oxitec’s tetracycline-dependent mosquitoes survive—what happens if those bugs breed with wild mosquitoes?
It’s even possible that the changes we induce in mosquitoes could move into other animals. Horizontal gene transfer could result in midges, gnats and black flies developing the same mutations, including the unfortunate characteristic of dying shortly after hatching—and a mass die-off of insects that provide sustenance to birds, bats, frogs and fish would be a food-chain disaster.
