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Dengue researchers turn to mosquito-killer fungus


Mosquito head covered in fungus

Head and mouthparts of mosquito infected with Beauveria bassiana

The Queensland Institute of Medical Research has been investigating whether a common fungus has a role to play in stopping the spread of dengue fever.

Dr Jonathan Darbro, from QIMR’s Mosquito Control Laboratory,  said initial testing showed the Beauveria bassiana fungus killed Aedes aegypti, the mosquito which carries the viral disease.

In laboratory and “semi-field” conditions, the soil fungus also reduced how often the mosquitoes bit humans.

Dr Darbro said the results offered a potential alternative to pesticides to control the mosquito-borne borne viral disease.

“The results are very promising,” he said.

“The fungus doesn’t kill the mosquitoes as quickly as a chemical product.  But because it kills slowly, mosquitoes are less likely to evolve a defence against the fungus.

“They’ll still live long enough to reproduce, so natural selection isn’t pushing as hard for the mosquitoes to resist the fungus as they would for a chemical insecticide.”

Each year there are more than 50 million global cases of dengue and its more severe form,  dengue haemorrhagic fever,  annually.  The virus kills 20,000 people each year.  There is no vaccine, and prevention relies almost exclusively on controlling the mosquito carriers.

Beauveria bassiana has long been used to control agricultural pests, and it’s also being considered in malaria studies. But this is the first time there has been semi-field testing on  Aedes aegypti, in outdoor cages in far north Queensland.

Dr Darbro said the next challenge would be finding a way to infect mosquitoes en masse.

“Mosquitoes need to land on the fungal spores to get infected.  Spores can be sprayed onto surfaces such as cloth, but they need to be surfaces where these mosquitoes would land in the wild. The most likely candidates would probably be places where mosquitoes would land to rest or lay eggs,” Dr Darbro said.

Dr Darbro’s study was published in The American Journal of Tropical Medicine and Hygiene, and made possible by a grant from the National Health and Medical Research Council (NHMRC).

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