Tue, Nov 12, 2013 - Page 9 News List

Researchers seeking to engineer dengue-immune mosquito

By Margie Mason  /  AP, TRI NGUYEN ISLAND, Vietnam

Yet how would it work in dengue-endemic areas of Southeast Asia? The disease swamps hospitals in the region every rainy season with thousands of sick patients, including many children, sometimes killing those who seek help too late.

The Australians tapped 58-year-old Yen at Vietnam’s National Institute of Hygiene and Epidemiology, where she has worked for the past 35 years. Their plan was to test the Wolbachia mosquitoes on a small island off the country’s central coast this year, with another release expected next year in Indonesia.

Just getting the mosquitoes to Tri Nguyen Island was an adventure. Thousands of tiny black eggs laid on strips of paper inside feeding boxes had to be hand-carried inside coolers on weekly flights from Hanoi, where Yen normally works, to Nha Trang, a resort city near the island. The eggs had to be kept at just the right temperature and moisture. The mosquitoes were hatched in another lab before finally being transported by boat.

Yen insisted on medical checks for all volunteer feeders to ensure they were not sickening her mosquitoes. She deemed vegetarian blood too weak and banned anyone recently on antibiotics, which could kill the Wolbachia.

“When I’m sleeping, I’m always thinking about them,” Yen said as she hunkered over a petri dish filled with dozens of squiggling mosquito pupae. “I’m always worried about temperature and food. I take care of them same-same like baby. If they are healthy, we are happy. If they are not, we are sad.”

Recently, there have been several promising new attempts to control dengue. A vaccine trial in Thailand did not work as well as hoped, proving only 30 percent effective overall, but it provided higher coverage for three of the four virus strains. More vaccines are in the pipeline. Other science involves releasing genetically modified “sterile” male mosquitoes that produce no offspring, or young that die before reaching maturity, to decrease populations.

Wolbachia could end up being used in combination with these and other methods, including mosquito traps and insecticide-treated materials.

“I’ve been working with this disease now for 40 something years and we have failed miserably,” said Duane Gubler, a dengue expert at the Duke-NUS Graduate Medical School in Singapore who is not involved with the Wolbachia research. “We are now coming into a very exciting period where I think we’ll be able to control the disease. I really do.”

Wolbachia also blocks other mosquito-borne diseases such as yellow fever and chikungunya, O’Neill said. Similar research is being conducted for malaria, although that is trickier because the disease is carried by several different types of mosquitoes.

It is unclear why mosquitoes that transmit dengue do not naturally get Wolbachia, which is found in up to 70 percent of insects in the wild. Yet O’Neill does not believe that purposefully infecting mosquitoes will negatively impact ecosystems. He said the key to overcoming skepticism is to be transparent with research while providing independent risk analyses and publishing findings in high-caliber scientific journals.

“I think, intuitively, it makes sense that it’s unlikely to have a major consequence of introducing Wolbachia into one more species,” O’Neill said, adding that none of his work is for profit. “It’s already in millions.”

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