Wed, Jul 18, 2012 - Page 9 News List

GM solution to dengue fever has fans and foes

Dengue fever kills about 20,000 people every year, but Oxford-based scientists think they can eradicate the problem by adding genetically modified insects to disrupt breeding in high-risk areas. Will that be safe?

By Conal Urquha  /  The Observer

Illustration: Mountain People

Behind an unmarked door at the side of an anonymous World War II Nissen hut in the middle of Oxfordshire, England, a group of scientists are attending to the needs of hundreds of thousands of mosquitoes. They provide horse blood for the females to feed on, moist beds for them to lay their eggs and add genes that transform the mosquitoes into what could be the most decisive tool yet invented to combat mosquito-borne disease.

The mosquitoes developed and raised here at the laboratories of Oxford Insect Technologies (Oxitec), a British biotech company based near Didcot, have already infiltrated wild populations in Brazil, Malaysia and the Cayman Islands, and will soon be unleashed in Panama and India. The company hopes that it will reduce populations of disease-carrying mosquitoes by 80 percent, but public opposition to anything “genetically modified” (GM) remains a significant obstacle to the possibility of saving thousands of lives.

Mosquito-borne diseases are one of the major barriers preventing economic progress in the developing world. According to the WHO, 200 million people were victims of malaria in 2010 and 655,000, mostly children, died from it. Dengue fever is believed to affect between 50 million and 100 million people a year and results in about 20,000 deaths.

“From a scientific point of view and an environmental sustainability point of view, we think we have a really good solution to the problem,” Oxitec chief executive officer Hadyn Parry says.

The company, which emerged from Oxford University in 2002, is primarily focused on dengue fever, which can cause excruciating pain and death, and the Aedes aegypti mosquito, which carries it. A. aegypti was mostly found in Africa until about the time of World War II. After that, it was transported by ships all over the world. A. aegypti can now be found in 110 countries and the incidence of dengue fever has risen 30-fold in the past 50 years.

The mosquitoes live near humans and lay eggs in any container holding water in and around homes — from as little as the residue left on a teaspoon to puddles in old tires. Eggs can survive for months after the water evaporates. The mosquitoes prefer small pools of still water that contain rotting organic matter. In their 10-day lives, they have little contact with species other than mammals and their eradication leaves the ecosystem much as it was before they arrived, Oxitec believes.

The main weapons against A. aegypti, pesticides and education, have had little success in preventing its spread. Pesticides are only effective when the mosquitoes can be seen and touched with spray. Educating people to empty any vessel around the home that could contain water is only as effective as the diligence of the individuals involved.

More sophisticated methods of control began after World War II, when scientists in the US began using radiation as a means of controlling insects. Sterilized male insects would then be introduced into the environment to mate with wild females. No offspring would be produced and the productive capacity of a female insect would be lost. The difficulty was in finding the right amount of radiation to sterilize the insect, but not damage him so much that he would be unattractive to females. The scientists achieved this with fruit flies and other insects, but did not succeed with mosquitoes, which were too feeble after sterilization to compete in the wild.

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