Vietnam fights dengue fever with virus resistant mosquitoes

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A jar of mosquitoes with viral resistant Wolbachi bacteria is placed in a house on Tri Nguyen Island under a project to inhibit the spread of dengue fever. Photo by Thu Huong

It looks like a piece of news from Ripley's "Believe it or not" collection, but islanders off the central town of Nha Trang are breeding a kind of mosquito that can help prevent dengue fever.

Tri Nguyen, located around two kilometers offshore from the famous tourist destination, has been chosen as the site for a scientific research project to try and replace the current species of mosquito on the island with new ones that carry Wolbachi, a bacteria genus that has been linked to viral resistance in mosquito species.

"It will open up opportunities for effective prevention of dengue fever not just in Khanh Hoa Province but the whole country," said Le Huu Tho, deputy director of the province's health department that is carrying out the project in collaboration with the National Institute of Hygiene and Epidemiology and Nha Trang Pasteur Institute.

Around 800 families on the island have been given 8,000 larvae of the dengue fever mosquito Aedes aegypti into which the bacteria has been introduced.

The research posits that Wolbachi-carrying mosquitoes will grow and become a new dominant Aedes aegypti community on the island in three months, limit dengue fever risks, and go on to eliminate the disease in the area.

The team said it took them seven years just to put the bacteria inside the mosquito larvae, as the implant could be done only one or two larvaes among every thousand .

Sixty coordinators, residents of the island, spent nearly three months to kill the normal Aedes aegypti mosquitoes on the island to reduce its number to less than 10 percent.

Health Ministry statistics show that dengue fever infects around 50,000 people every year, killing around 50. Khanh Hoa Province is the hardest hit in the central region with 5,300 infections including five fatalities last year.

There have been 10,847 dengue fever infections reported nationwide so far this year, up 5.2 percent year-on-year. There have been 10 deaths. Khanh Hoa and Ho Chi Minh City are among the localities with highest infections.

Nguyen Van Hai, director of Khanh Hoa Preventive Health Center, said the island was selected not only because of its own dengue fever situation.

"The main reason is that its provides an ideal community - moderate population in a small area which is detached but not too far from the mainland."

A research team member said they first planned to use mosquitoes from Australia, where a similar program was the first successful one recorded in the world, but they feared the creatures might not survive the shift in climatic conditions. They ended up using mosquitoes from the island itself.

He said the research project is being carried out because traditional measures against dengue fever such as killing its larvae with chemical solutions and sprays are outdated.

The mosquitoes are developing resistance to the chemicals and are only dying in high doses. "But any chemical should only be used in the worst scenario situation, as spreading toxins also affects people's health."

China and Brazil have also gained positive results from such projects, and Singapore and Thailand are starting similar ones as well, he noted. While these nations have used their own state budget funds, Vietnam's project is sponsored by Family Health International, a US-based non-governmental organization specializing in public health issues.

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