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Dengue trial awaits ministry’s nod

A researcher feeds mosquitoes infected with naturally occurring bacteria Wolbachia in a lab in Australia.
A researcher feeds mosquitoes infected with naturally occurring bacteria Wolbachia in a lab in Australia. Steve Morton/Monash University

Dengue trial awaits ministry’s nod

A new and cost-effective form of dengue control that has shown promising results in trials around the world could be applied in Cambodia, according to scientists and the World Health Organization – if it is given approval by the Ministry of Health.

The technology, developed by the non-profit World Mosquito Program based out of Australia’s Monash University, involves infecting Aedes aegypti mosquitoes with naturally occurring bacteria called Wolbachia that inhibit the transmission of viruses like dengue fever and does not affect humans. The mosquitoes would then be released into the wild.

Speaking at a Pasteur Institute seminar in Phnom Penh in late October, Dr Peter Ryan, the WMP’s business development director, said that ongoing trials in Australia, Brazil, Colombia, Indonesia and Vietnam have shown “promising” results, with a near total reduction of dengue transmission in affected areas after two to three years. It was piloted in 2011 in Australia.

“There’s a range of other sites [where] we’d like to undertake field trials in another year and perhaps near in the future here in Cambodia,” he said.

Trials in Brazil and Colombia have shown that Wolbachia may also interrupt the transmission of viruses like Chikungunya and Zika, which have both been documented in the Kingdom.

In trial areas, residents give consent beforehand and even participate in releasing the mosquitoes. Once enough mosquitoes are present, the microbe will naturally go on to infect the local mosquito population.

“Eventually close to 100 percent of insects in that area have Wolbachia inside them and it will sustain itself in the local area,” he said.

Eliminate Dengue program representatives speak to community members in Vietnam.
Eliminate Dengue program representatives speak to community members in Vietnam. Eliminate Dengue

The cost the WMP aims for is a long-term investment of about $1 per resident. By comparison, dengue control costs in Phnom Penh and Kandal associated with spraying insecticides and larvicides – which provide temporary solutions – run closer to $0.20 per person per year.

According to Pasteur Institute Director Didier Fontenille, there is a pressing need for the Kingdom to explore methods to control carriers of disease beyond using insecticides and larvicides.

He wrote by email that yet-to-be published data from the Pasteur Institute, Malaria Consortium and National Malaria Centre (CNM) showed that Aedes aegypti are resistant to two major insecticides used in Cambodia – a resistance suspected since 2001.

“For me it is a very good initiative due to difficulties to control mosquitoes efficiently with current tools,” he said.

This assessment was shared by Dr Luciano Tuseo, the head of the WHO’s Cambodia dengue programme.

“It’s urgent to implement new forms of vector control for dengue. Wolbachia technology maybe can answer this need,” he said. Despite the technology being relatively new, the WHO’s official recommendation is for “carefully planned pilot deployment” independently monitored and evaluated for both control of dengue and Zika.

Fontenille wrote that if the Ministry of Health and CNM were to implement a Wolbachia study in Cambodia, the Pasteur Institute would be able to lend its expertise as a close partner to the project. A ministry spokesman referred questions to CNM Director Huy Rekol, who could not be reached.

“[The] Ministry of Health have the capacity to pilot [a] Wolbachia pilot project in Cambodia, [but] support by partners will be essential,” Tuseo wrote.

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