Wolbachia bacteria protect mosquitoes against dengue

Queensland researchers have prevented mosquitoes from spreading dengue fever by infecting them with a naturally occurring bacterium.

In collaboration with The University of Queensland, QIMR scientists have found that the Wolbachia bacteria prevent Aedes aegypti mosquitoes from becoming infected with dengue virus, and means that the mosquitoes can’t transmit the virus to humans.

Dr Peter Ryan from the Mosquito Control Laboratory at QIMR worked on the study, which was published in the 24 December edition of Cell.

“We discovered that infecting the Aedes aegypti mosquitoes with Wolbachiaprevented the virus from replicating inside the mosquitoes. The bacteria act like a barrier which prevents the mosquitoes from becoming infected with dengue virus,” said Dr Ryan. “It’s likely that the bacteria primes the mosquitoes immune system or competes for limited resources and prevents the virus from multiplying.”

“Wolbachia live naturally in 60% of insect species, but do not naturally infect the species of mosquito that carry the dengue virus.”

Dengue and the more severe form, dengue haemorrhagic fever lead to 50 million cases and cause 20,000 deaths worldwide every year. As there are no vaccines for this virus, prevention of this illness relies almost exclusively on controlling the mosquito carriers. Dengue is an increasing problem and is becoming more widespread, with a greater number of outbreaks and increasing symptom severity.

Previous studies found that the Wolbachia bacteria shortened the life span of the adult mosquitoes, making it less likely to live long enough to transmit these infections.

“Our recent findings work in tandem to this. By shortening the lifespan as well as preventing the mosquito becoming a carrier for these viruses should, not only prevent the spread of the dengue virus, but also reduce the risk of the mosquitoes developing resistance to the treatment,” said Dr Ryan.

This research aims to help to provide long term solution to reduce the incidence of mosquito-borne diseases without the use of insecticides.

A pilot field study is planned for Australia, Vietnam and Thailand in the near future.

The paper was published in the 24 December 2009 edition of Cell.