Stopping dengue at its source

Professor Scott O'Neill

By protecting mosquitoes from dengue fever, scientists have potentially found a way of preventing the 50 million human cases of the disease reported every year.

With no specific antiviral medicines available to treat the disease, and more than two billion people living in dengue transmission zones, the breakthrough could save thousands of lives in the developing world.

In a world-first trial, an international collaboration of researchers working on the Eliminate Dengue program, have successfully transferred promising laboratory results to wild mosquito populations, bringing their goal much closer.

The research, led by Professor Scott O’Neill, Dean of Monash University’s Faculty of Science, was published today in the prestigious journal, Nature.

“Current control methods, largely based around insecticide use, are failing to stop the global dengue problem.

“We hope to develop a new control method that could provide a practical, sustainable and cost-effective approach to dengue suppression around the world,” said Professor O’Neill.

The team aims to protect the mosquitoes themselves from dengue and so stop them transmitting the virus to humans. To do this, Wolbachia, a natural bacterium known to reduce mosquito susceptibility to dengue, was introduced to wild populations ofthe mosquito that transmits the disease.

“Years of laboratory experiments had shown that we could introduce Wolbachia into the mosquito. It then passed from one generation to the next in the mosquito egg.

“The research published today describes the successful establishment of a particularly promising Wolbachia strain within the dengue mosquito in the lab, its subsequent ability to reduce dengue transmission potential of the mosquito, and also the successful introduction of the same Wolbachia strain into wild mosquito populations in Australia.”

In January this year, with community support and appropriate regulatory approval, mosquitoes carrying Wolbachia were released in two suburbs in Cairns, Queensland. Within three months period Wolbachia hadsuccessfully invaded the local mosquito populations.

“The field trial involved releasing Wolbachia mosquitoes every week for 10 weeks. Five weeks after the final release it was determined that 100 per cent of the mosquitoes at one site carried Wolbachia and 90 per cent at the other. That was a great day,” said Professor O’Neill

“These findings tell us that Wolbachia-based strategies are practical to implement and might hold the key to a new sustainable approach to dengue control, an approach that should be particularly suited to large cities of the developing world where conventional control with insecticides is largely ineffective and prohibitively expensive.”

Further trials will be conducted in Cairns over the coming wet season and approval is currently being sought for trials in Thailand, Vietnam, Brazil and Indonesia that will directly determine the effectiveness of the method in reducing dengue disease in human populations.