Scientists develop method of blocking transmission of mosquito-borne virus

An effective way to block the transmission of the mosquito-borne dengue virus has been developed by scientists in Scotland and Australia.

Researchers at the Universities of Glasgow and Melbourne worked with the Institute for Medical Research in Malaysia to conduct trials in Kuala Lumpur using a strain of the bacteria wolbachia.

After mosquitoes carrying the wAlbB strain were released into the wild, the number of dengue cases reduced by 40%.

Batches of aedes aegypti mosquitoes – both male and female – carrying the strain were released into the wild at six different sites before mating with the wild mosquito population – resulting in the spread and establishment of the virus-inhibiting bacteria.

Previous research used a different strain which, while effective in some conditions, did not appear suitable for very hot conditions experienced in equatorial countries such as Malaysia.

Professor Steven Sinkins, of the MRC-University of Glasgow Centre for Virus Research, is lead contact for the new study.

He said: “We are excited by these findings, which show that we have a strain of wolbachia that can be used to effectively reduce the number of dengue cases in very hot climates.

“The next step is to deploy this strain in more and larger sites, but we are now confident that this will become an effective way to control dengue on a large scale.”

Each year, around 90 million symptomatic cases of dengue are reported, with 1% of those severe – including life-threatening haemorrhage or shock syndrome.

In Malaysia alone, more than 100,000 dengue cases were reported in 2016, with an annual cost estimated at 175 million US dollars (£135.5 million).

Professor Ary Hoffmann, one of the three lead contacts for the study from Melbourne’s Bio21 Institute, said: “This study provides us with a new wolbachia strain for field release and highlights disease impact within a complex urban setting where dengue incidence rates are high.

“The intervention succeeded despite ongoing pesticide applications and other challenges that can make it hard for the wolbachia to become established, and the approach holds promise not only in Malaysia but also in other countries.”

The paper, Establishment of Wolbachia Strain wAlbB in Malaysian Populations of 2 Aedes Aegypti for Dengue Control, is published in Current Biology and funded by the Wellcome Trust.

Michael Chew, infection and immunobiology portfolio manager at Wellcome, said: “These findings mark important progress in the future of dengue fever control.

“It is exciting to see, for the first time, a strain of wolbachia successfully reduce the number of dengue cases in very hot climates in the wild.

“The unprecedented rise of dengue worldwide make control methods such as these a vital addition to the tools we currently have to tackle one of the fastest-spreading mosquito-borne viral diseases.

“It is crucial that local communities and the Malaysian Government continue to provide their support, which will be key for the long-term sustainability in controlling dengue on a large scale.”