The Destroying Garden / Bijal P. Trivedi

A new breed of mosquitoes, which have been genetically engineered, carry a gene that cripples their offspring. They may crush natural mosquito populations and prevent the spread of disease. And they are already among us, although this is kept a secret

Near the city of Tapachula in the state of Chiapas in Mexico - 16 kilometers from Guatemala.

To get to the cages, we leave the city on the main road that passes through plantations and fields bright in the deep green of soy, cocoa, banana and mango trees that thrive in the rich volcanic soil. After passing the tiny village of Rio Florida, the road deteriorates into a winding dirt path and we begin to jump over waves of frozen mud to a security post with an alert guard. On the barbed wire fence delimiting the facility there is a sign on which a mosquito is drawn with the figures of a man and a woman on either side. On the sign it says: Estos mosquitos genéticamente modificados requiem un manejo especial (these mosquitoes have undergone genetic engineering and they require special treatment). We follow the procedures.

Inside, a set of mesh cages is placed on a surface surrounded by cashew trees. In the cages there are thousands of mosquitoes of the local species, Aedes aegypti, which is a smaller and quieter species than their buzzing counterparts in the United States. At seven in the morning, the landscape looks heavenly: rays of sunlight filter through layers of nets and cast a glowing yellow light. But inside the cages, a war of attrition is taking place that prohibits mosquitoes that have undergone genetic engineering in the local mosquitoes. This is an experiment in the destruction of a species through mating, to burn dengue fever, one of the most disturbing and violent diseases in the world.

In the belt of tropical and subtropical countries, there are four dengue viruses that are very similar to each other, which infect about 100 million people every year. The virus causes diseases with a variety of symptoms: from pains similar to flu to internal bleeding, shock and death. The disease has no vaccine or cure. As with other mosquito-borne diseases, the primary strategy for maintaining public health is to prevent bites. For this purpose, the authorities are trying to drain stagnant water from the neighborhoods, where the insects breed, spray with mosquito killers and distribute nets and other simple aids as a barrier against the mosquitoes. The goal is to slow down the disease, not eradicate it.

However, Anthony James plans an attack. James, a molecular biologist at the University of California, Irvine, and his colleagues add genes to the A. aegypti virus that suppress the development of the flight muscles in females. When a genetically engineered male mosquito mates with a wild-type female, it passes its engineered genes to the offspring. The damaged females, which are the ones meant to sting, do not survive long. When they hatch after the pupal stage, they sit motionless on the water. They do not fly, mate or spread the disease. In contrast, the male offspring get to live and spread their deadly seed. In time, the absence of females will cause the population to crash, as James' colleagues have already demonstrated in the controlled environment of a Colorado laboratory. Now he moved his mosquitoes south.

This technology marks the first time that scientists have created, through genetic engineering, an organism whose goal is to exterminate an entire natural population to prevent the transmission of disease. If the genetically engineered mosquitoes win, their release in dengue-stricken areas around the world could prevent hundreds of millions of people from suffering. But opponents of the plan warn of unintended consequences, even if the intended victims are mosquitoes.

Researchers are also struggling to find a way to test their creation. There are no international agencies or international laws aimed at overseeing experiments with new transgenic organisms. For the most part, scientists and biotech companies can do as they please and even uncontrollably release the experimental creatures in developing countries, without warning the residents that their backyard is about to become a biocolonialist field laboratory, and without obtaining their consent.

James spent years trying to play by the rules. He partnered with community leaders in Tapachula, purchased property through a traditional land-sharing scheme, and built a secure testing facility, all with an investment of labor and time. But he is not the only researcher testing genetically engineered mosquitoes outside the laboratory. One of James's colleagues, Luke Alfie, founder of the British biotechnology company Oxitech, is secretly taking a more aggressive testing strategy. In 2009 and 2010, his company took advantage of the paucity of installations on the island of Grand Cayman in the Caribbean to release millions of genetically engineered mosquitoes into the wild. James first found out about the experiments when Alfie described them at a conference in Atlanta in 2010 – 14 months after the fact. Since then, Oxitec has continued experiments and released transgenic mosquitoes in Malaysia and Brazil.

Experts fear that Oxitec's actions will achieve the opposite goal and cause a complete reluctance to use any genetically engineered insects, similar to Europe's refusal to use genetically engineered crops. Such a scenario could eliminate the technology even before scientists can fully understand both its potential and possible consequences.

And that would be unfortunate, because this is a very promising technology. The experiment in Colorado proved that the genetically modified mosquitoes are indeed effective in a controlled environment, although some cages are not equivalent to the areas of Central America, Brazil or Malaysia. To combat the disease and death that the mosquitoes carry within them, the scientists' handiwork must defeat the jungle.

And more on the subject

Building the Better Bug. David A. O'Brochta and Peter W. Atkinson in Scientific American, Vol. 279, no. 6, pages 90–95; December 1998.

Insect Population Control Using a Dominant, Repressible, Lethal Genetic System. Dean D. Thomas et al. in Science, Vol. 287, pages 2474–2476; 2000. www.sciencemag.org/content/287/5462/2474.abstract

Genetic Elimination of Dengue Vector Mosquitoes. Megan R. Wise de Valdez et al. in Proceedings of the National Academy of Sciences USA, Vol. 108, no. 12, pages 4772–4775; March 22, 2011. www.pnas.org/content/108/12/4772.full

Genetic strategies to control the spread of dengue.