Dengue Fever and Genetically Modified Mosquitoes: Decrease?

No more deadly biting for you, buzzers. Or at least, that is surely the summer-time thought of researchers who published a recent report in PLOS: Neglected Tropical Diseases about their work modifying mosquitoes in the fight against dengue fever--which which infects up to 50 million people annually, according to the World Health Organization. 

The scientists' study involves modifying male mosquitos so that their young dies quickly. Tests involving these GM mosquitoes are currently taking place in the Brazilian city of Piracicaba. The researchers also hope to receive permission from the FDA to test the mosquitoes on one of the Florida Keys. 

When the modified mosquitoes mate with native females, they pass on a gene to offspring that causes the larvae to die before they're fully grown. The mosquitoes were designed by the company Oxitec of Abingdon, UK; they are bred in a factory in Campinas, Brazil, according to the company.

Since April 6, 6 million of the GM mosquitoes have been released in a badly infested area of Piracicaba. A recent trial in a Juazeiro, Brazil suburb showed that the native population decreased by 95 percent in six months, according to a release. 

Researchers measure the impact by checking pots of water in which mosquitoes lay eggs; they count the proportion of red larvae to determine how effectively the native population is being decreased, according to the release.

Recent results from the pot-survey show that half the local larvae have been sired by the modified mosquitoes. Scientists are still looking at whether decreasing the carrier number will minimize the disease transmission, according to the release.

"In theory, if you have fewer mosquitoes you have less transmission, but in reality, this is something we still need to investigate," says Margareth Capurroof of the University of Sao Paulo, and head of the Brazilian team that conducted the Brazilian-funded trial on behalf of Oxitec in Juazeiro, according to New Scientist magazine. "You can have lots of mosquitoes with only a few infected, or very few with all of them infected," she says. "If this happens, you suppress the population but don't affect dengue transmission."

Laith Yakob of the London School of Hygiene and Tropical Medicine says the results are impressive, although the effect could be temporary, as it is with chemical spraying-because of mosquitoes' movements into the area from elsewhere.

Follow Catherine at @TreesWhales