Introducing bacteria in mosquitoes cuts dengue cases by 77%, study finds

Dengue cases have been slashed by 77 per cent in areas where scientists introduced mosquitoes infected with certain bacteria in a trial.

Hospital admissions for dengue - which causes joint pain, a high temperature and severe headache  - also fell dramatically in the parts of Indonesia where mosquitoes with Wolbachia were released, according to the study’s findings.

Researchers said the trial was a “great success” and showed “what an exciting breakthrough” this bacteria can be.

“We think there is a possible future where residents of Indonesian cities can live free of dengue,” Professor Adi Utarini from the University of Gadjah Mada, co-principal investigator, said.

Wolbachia are bacteria naturally found in 60 per cent of insect species and also safe for humans , according to the World Mosquito Programme, who were also involved in the latest study.

Aedes aegypti mosquitoes - the main transmitter of dengue - do not normally carry this bacteria, although other types of mosquitoes do, according to the non-profit group.

In the trial in Indonesia, researchers looked at whether introducing Wolbachia into the local mosquito population that transmits dengue would reduce cases among under-45s.

Researchers said they found the strain of Wolbachia introduced “was effective in reducing the incidence of symptomatic dengue”, according to findings published in The New England Journal of Medicine on Thursday.

The trial found the incidence of dengue dropped by 77 per cent in areas of Yogyakarta where Wolachia-infected mosquitoes were released.

Meanwhile, dengue cases resulting in hospitalisation dropped by 86 per cent, according to the study carried out by the University of Gadjah Mada in Indonesia and the World Mosquito Programme from Australia’s Monash University.

“This is a great success for the people of Yogyakarta. Indonesia has more than seven million dengue cases every year,” Prof Utarini said.

Professor Scott O’Neill, the director of the World Mosquito Programme who has been working on Wolbachia and dengue for more than four decades, said it was “the result we’ve been waiting for”.

“We have evidence our Wolbachia method is safe, sustainable and dramatically reduces incidence of dengue,” he said.

“It gives us great confidence in the positive impact this method will have worldwide when provided to communities at risk of these mosquito-transmitted diseases.”

According to the World Health Organisation (WHO), some people infected with dengue may not release they have it, while others can have severe flu-like systems.

Less commonly, it can lead to severe dengue, which has a higher risk of death when not treated properly and come with complications linked to severe bleeding and organ impairment, the WHO says.

The World Mosquito Programme aims to protect the global community from mosquito-borne diseases by using the so-called Wolbachia method.

The non-profit initiative says this bacteria competes with viruses - such as dengue and Zika - in mosquitoes and makes it harder for these to replicate.

It then becomes “much less likely” mosquitoes will spread these viruses among humans, the World Mosquito Programme says.

Its researchers breed Aedes aegypti mosquitoes to carry Wolbachia and release them into areas affected by mosquito-borne diseases in partnership with local communities.

The WHO says dengue has “rapidly spread” in all of its regions in recent years.

Amid lockdowns in southeast Asia last year, cases jumped in tropical regions where dengue is most common, with experts suggesting the Aedes mosquito may have been thriving due to restrictions stopping communities from cleaning up stagnant water and detritus.