Posted: 25 August 2011
PARIS - Scientists say they've found on a new way of controlling dengue fever by weakening populations of mosquitoes carrying the virus which causes the deadly disease.
"The results show we can completely transform local (mosquito) populations in a few months," said Michael Turelli, a biologist at the University of California at Davis. "It's natural selection on steroids."
Dengue which affects between 50 and 100 million people in the tropics and subtropics each year, is caused by four strains of virus that are spread by the mosquito Aedes aegypti.
There is no vaccine, which is why scientists are focussing so intensely on mosquito control.
In 2009, Turelli and others hit on the idea of inserting a naturally-occurring bacterial parasite called Wolbachia to shorten the mosquito's lifespan so that the virus would not have enough time to develop.
After initial setbacks, the team of scientists found a non-virulent strain of Wolbachia in the fruitfly Drosphila.
Introduced into the mosquito, the germ prevented the insect from becoming infected by the dengue virus.
At the same time, the Wolbachia which is a symbiotic bacterium, it was also harmless to the mosquito as it exists by living in harmony with its host.
As it lives inside cells and is maternally inherited, this raises the possibility that after a few generations, the introduced dengue-free mosquitoes eventually outnumber dengue-carrying counterparts.
After long consultations with the government and regulators, the scientists released Wolbachia-infected mosquitoes in two locations in Queensland, Australia, this year.
Early results suggest that the introduced mosquitoes have thrived, and "herald the beginning of a new era in the control of mosquito-borne diseases," said Jason Rasgon, a specialist at the Johns Hopkins Malaria Research Institute, Maryland, in a commentary also carried by Nature.
"The advantage of population-replacement approaches is that, once established, they are self-propagating. And because the mosquito population is simply changed rather than eliminated, effects on the ecosystem should be minimal."
The paper appears in Nature, the weekly British science journal.
- AFP/sf
Taken from ChannelNewsAsia.com; source article is below:
Dengue fever under attack through smart mosquito control
Just make sure you don't get bitten, not by insects, not by animals, nor even humans! But would you carry dirty clothes?
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Posted: 02 June 2011
PARIS - In the biggest lab breakthrough against malaria in years, scientists on Wednesday said they had identified odour molecules that baffle blood-thirsty mosquitoes.
The molecules disrupt carbon-dioxide sensors that alert mosquitoes to exhaled breath, which signals the presence of a human nearby, the team reported.
The work could lead to revolutionary but low-cost chemicals to confuse, deter or trap mosquitoes, it said.
They could be invaluable in poor tropical countries, providing an alternative to DEET, a skin repellent that is expensive, needs repeat applications and is showing worrying signs of resistance.
"These chemicals offer powerful advantages as potential tools for reducing mosquito-human contact and can lead to the development of new generations of insect repellents and lures," said Anandasankar Ray, an assistant professor of entomology at the University of California at Riverside, who led the study.
Traps for mosquitoes already exist, in the form of dry ice, gas cylinders of carbon dioxide or propane combustion.
But these gadgets are too bulky and far too expensive to be used for mosquito control, especially in poor settings.
Future mosquito traps, Ray predicted, could be "highly portable, convenient and easily replenishable."
Malaria claimed 781,000 lives in 2009, according to the UN's World Health Organisation (WHO), which is heading efforts to distribute insecticide-treated mosquito nets and to spray reproduction sites.
About 90 percent of malaria deaths each year occur in Africa and 92 percent of those are children aged under five.
Other mosquito-borne diseases are dengue, which sickens around 50 million people each year, yellow fever, filariasis and West Nile virus.
Building on research on fruitflies, a common laboratory tool, Ray's team looked at three of mosquito species whose females are disease vectors: Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus.
The odour molecules that they identified disrupt receptor cells for carbon dioxide located in tiny, antennae-like appendages close to the mosquito's mouth.
These receptors are activated by a whiff of carbon dioxide, triggering a signal in the brain that prompts the insect to fly upwind, following the puffs of CO2 until they reach its source. Mosquito also use heat sensors and sight to home in on their meal.
The findings have been tested in a small-scale experiment in Kenya, using huts where alluring plumes of CO2 were released to attract mosquitoes and odour molecules were released to bamboozle them.
Mark Stopfer, a specialist at the US National Institutes of Health (NIH), said the results opened up "a promising line of defence."
He added some words of caution, saying that mosquitoes were attracted to other odours in human sweat and skin. In addition, the chemicals that have been tested on insects so far have not yet been tested for safety on humans, he noted.
-AFP/rt
Taken from ChannelNewsAsia.com; source article is below:
Mosquitoes are suckered in new malaria research
