Genetically Modified Mosquitoes Released in Malaysian Forest

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An alternative to mosquito fumigation? (AP)

A government-run institute in Malaysia announced this week that it had released 6000 genetically modified mosquitoes into an uninhabited patch of forest in December to combat dengue fever.

The experiment, which is now over, was aimed at controlling the local mosquito population by having altered male Aedes aegypti mosquitoes mate with wild female mosquitoes, which carry the disease. The males were engineered so that the females they impregnated would either not have offspring, or have offspring with shorter lives.

Malaysian officials told the AP that it was the first experiment of its kind in Asia. But genetically modified insects have been released into nature before. In the Cayman Islands, GM mosquitoes were released last year with the same goal of reducing the local population (it seemed to work), and in 2006, the U.S. released GM pink bollworms, a common cotton pest, with marker genes in the first use of GM insects in a plant pest control program.

The potential benefits of controlling disease through GM insects are big. Malaria, for which there is no known vaccine, kills at least a million people each year, mostly in Asia and Africa. In some countries where transmission levels are high, the mosquito-born disease is estimated to cost up to 1.3% of GDP annually. Crop and livestock pests, too, have enormous economic impacts. (See pictures from TIME on the global fight against malaria.)

The sometimes-fatal dengue fever, which the Malaysia experiment was designed to target, infects between 50 to 100 million people every year. Though it’s not as dangerous as malaria, it’s been on the rise in recent years; the number of dengue related deaths in Malaysia in 2010 was up over 50% from the year before. Areas where dengue is present often have to deal with regular, noxious fumigations of their neighborhoods. The GM option offers one alternative.

This is a good summary of how the method works from the UK’s Parliamentary Office of Science & Technology. (No GM insects have been approved for release in the EU.)

Population suppression is a method in which insects are engineered to ensure that when they mate with wild individuals no viable offspring are produced. This is achieved by creating GM insects carrying a lethal gene. When they mate with the wild  insects the lethal gene, which is suppressed before release, is passed to the offspring causing them to die. If enough of the GM males were to be released to inundate the wild females this would result in the elimination of the insect population from the area. Most suppression strategies are self-limiting because the lethal genes are designed to kill successive generations,  eventually removing all the GM individuals from the wild.

The genetic manipulation and release of insects, of course, has its detractors, too. Greenpeace, among others, has warned that the unknown risks of unleashing GM insects into the wild outweigh any benefits the technology offers. Critics worry that the space left by the population cleared out by GM popularion control may just give rise to a new mutation or a new disease, and point out that the effects of any experiment using GM insects are impossible to monitor. Existing international GM regulation designed to govern this technology currently only applies to GM crops, not insects, a fact which the parliamentary brief says “may slow down the development of these technologies or deter investment by preventing trial releases.”

Malaysia, for its part has said that its 6000-insect experiment is officially over, and that all the engineered mosquitoes released in the area have been killed with insecticide. They think. Stay tuned.