Swarms of genetically modified mosquitoes? This isn’t science fiction: The Malaysian government announced earlier this week that it unleashed 6,000 genetically modified (GM) skeeters into a forest as part of a plan to fight dengue fever, a potentially fatal affliction that can affect up to 100 million people each year.
The news appears to have caught the Malaysian media and public by surprise; many recent news stories reported that the study had been postponed after intense protests. As recently as 17 January, the Consumers’ Association of Penang and Sahabat Alam Malaysia, two groups opposing the use of GM insects, called on the National Biosafety Board to revoke its approval for the study. Scientists, too, were under the impression that the work had yet to begin, says medical entomologist Bart Knols of the University of Amsterdam. A 24 January blog post by Mark Benedict, a consultant at the Centers for Disease Control and Prevention in Atlanta who monitors the field closely, mentioned that the Malaysian study was “planned.” [ScienceNOW]
The study itself included the release of 12,000 male mosquitoes in total: 6,000 unaltered and 6,000 GM Aedes aegypti mosquitoes. The goal was to track how well the two types survived and how far they spread. U.K. biotech firm Oxitec created the modified mosquitoes, which don’t produce viable offspring. Researchers hope that if these altered males mate with wild females, it will bring the overall mosquito population down. The strategy has been tried once before in the Grand Cayman Islands, and results from that experiment are due to be published soon.
A mosquito‘s whiny buzz may be one of the most annoying noises to human ears, but for some mosquitoes it’s an intricate love song. A new study of the mosquito Aedes aegypti, which carries the infectious diseases dengue fever and yellow fever, has shown that when males and females mate they adjust the speed of their beating wings until their two buzzes combine to produce a harmonious tone. And this isn’t just gee-whiz science: Researchers say the finding could help in the fight against the disease-carrying insects.
The male mosquito’s buzz, or flight tone, is normally about 600 cycles per second, or 600-Hz. The female’s tone is about 400-Hz. In music, he’s roughly a D, and she’s about a G. So the male brings his tone into phase with the female’s to create a near-perfect duet. Together, the two tones create what musicians call an overtone — a third, fainter tone at 1200-Hz. Only then will the mosquitoes mate [NPR]. Researchers were surprised that the mosquitoes could detect the overtone, because they previously believed that A. aegypi males couldn’t hear frequencies above 800-Hz, and the females were thought to be completely deaf.
To combat the persistent scourge of dengue fever, researchers have infected the virus-carrying mosquitoes with a bacterium that kills them before they’re old enough to transmit the virus to humans. Researchers say this “biopesticide” technique could cheaply and quickly reduce deaths due to dengue fever in the tropics, as the bacterium could rapidly spread through mosquito populations. Traditional [malaria-oriented] methods for controlling the spread of mosquito-borne disease, such as using bed nets and draining wetlands, are ineffective for the Aedes aegytpi mosquitoes that spread dengue fever virus because they bite during the day and thrive in urban areas [Nature News].
While the new process has only been tested in the lab thus far, researchers are very optimistic about the possibility of whittling away at the 20,000 deaths caused each year by the disease, and say it’s conceivable that transmission of the virus could be reduced to nearly zero. “We’re not trying to eliminate the population, but to let a bacterial symbiont in, and then shift the population,” said University of Queensland bacterial geneticist Scott O’Neill. “There will still be mosquitoes around, but only young ones. It’s a biological control” [Wired News].