Dengue fever breakthrough

2011-08-25 18:15

Sydney - Researchers in Australia have found a possible way of blocking mosquitoes from infecting humans with dengue fever.

The new technique consists of infecting the mosquito carrier with bacteria that seem to stop the dengue virus from migrating to the parasite's saliva glands. This prevents it from passing it to humans.

A peculiarity of dengue fever, which affects 100 million people each year, is that the Aedes aegypti mosquito which carries it is not affected by the virus, remaining infected, and infectious, for life.

But the team led by Scott O'Neill, biology professor at Melbourne's Monash University, found that mosquitoes infected with a particular strain of Wolbachia, a bacterium commonly found in fruit flies, seems to stop the dengue virus being absorbed by the insect's gut.

"And this bacteria, we've found that when it's in the mosquito, it prevents the mosquito from being able to grow the dengue virus in its body," O'Neill told national broadcaster ABC.

"And if it can't grow it, then it can't transmit it between people."


The recent breakthrough was when the team released around 300 000 Wolbachia-infected mosquitoes in north-eastern Australia, and found that they passed the bacteria on to wild mosquitoes, according to a report published on Thursday in science magazine Nature.

"What we found is that over time all of the mosquitoes in those... localities ended up carrying this bacteria," O'Neill said.

Trials with previous strains of Wolbachia had shortened the insects' life span considerably, meaning that they had no chance to pass their dengue-resistant bacteria to other mosquitoes.

The research team was now keen to try out the new programme in Vietnam, Brazil and Indonesia, where dengue is endemic and deaths from the fever are in the tens of thousands.

There is no approved vaccine for the dengue virus and no effective treatments for the disease. So far, efforts have focused on stopping mosquitoes biting people and ridding environs of the stagnant pools of water where they breed.

O'Neill said it was not "fully understood" how the Wolbachia bacteria blocks the dengue virus, but that it could be because they compete for resources in the mosquito's metabolism.

The technique could be tried against the malaria virus as well, he said.