Project which ‘eliminates’ dengue extended to 3 more Pacific island nations

An Australian project which “all but eliminated dengue fever” in Far North Queensland has been successfully extended to Fiji, Kiribati and Vanuatu.

The program uses a naturally occurring bacteria called Wolbachia that modifies the ability of mosquitoes to carry the dengue virus. If the mosquitoes can’t carry the dengue virus, then they can’t transmit it between susceptible humans.

Wolbachia-carrying mosquitoes were released in the three Pacific Island states over the past few years and the latest research shows they have come to dominate the local mozzie population. It’s a step towards eliminating dengue, and while initial public health assessments suggest that the incidence of outbreaks has reduced, longer term monitoring is needed to demonstrate the positive outcome.

The project is run by the World Mosquito Program (WMP),  a not for profit operated by Monash University in Melbourne.

Dengue fever or dengue virus infection is an illness with symptoms that are like a bad case of the flu.  It’s caused by a virus carried by mosquitoes. These mosquitoes are mainly found in: Asia, Africa and South America.

The dengue-free mosquitoes were bred with the Wolbachia bacteria, says Cameron Simmons, an infectious disease scientist at Monash University and WMP’s Director of Global Implementation. The bacteria is passed on from generation to generation.

“It is not like an infectious disease among mosquitoes,” Simmons told Cosmos. “It doesn’t spread horizontally between mosquitoes like a sexually transmitted disease. Wolbachia very cleverly manipulates reproductive outcomes, so that over time, Wolbachia-carrying mosquitoes replace the local wild type population.

“Wolbachia is a bacteria that only lives inside the cells of insects. It can’t survive outside and can’t infect mammals or anything else.

“We transferred that into the Aedes aegypti mosquito, which doesn’t naturally carry Wolbachia, and what we discovered was that the mosquito is much more resistant to being infected with dengue virus or chikungunya virus or a Zika virus.”

Dengue fever is particularly dangerous for babies and children. In 2022 in Timor Leste there was a deadly outbreak that resulted in more than 50 deaths from 4787 cases. Nearly 90% of the victims were under 14.

“Most of the deaths in Southeast Asia occur in kids, well, children and young adults,” says Simmons.

“Most adults in the regions can get multiple infections and build immunity over time. I’ve had a couple of exposures. By the time you’re about 25 each of those exposures generates immunity and you become immune for life to the four dengue virus types.”

WMP developed the novel approach – to infect the mosquito population with Wolbachia – over the past decade and has completed small and large scale deployments in 14  countries in the Pacific, South East Asia and South America, including Laos, Indonesia, New Caledonia, Colombia, and Sri Lanka.

Simmons says results in the city of Medellin in Colombia were “spectacular,” and in Yogjakarta, in Indonesia, the local government is spreading the project statewide after a “very successful” trial which reduced the incidence of dengue by more than 80%.

Read more: The battle to defeat dengue in South America

The project releases about 2 to 4 Wolbachia infected mosquitoes for each member of the population, each week for about 5 months. It requires significant local community input. And funding.

The Indopacific Centre for Health Security wesbsite says DFAT supports the World Mosquito Program (WMP) to trial the use of Wolbachia bacteria to reduce the transmission of the dengue virus, as well as other arboviruses including Zika and chikungunya, in several countries in the Pacific (Fiji, Kiribati, and Vanuatu) and Southeast Asia (Sri Lanka, Indonesia).

“In addition to DFAT, WMP is supported by a range of government, corporate, and philanthropic donors, notably the Bill and Melinda Gates Foundation and the Wellcome Trust which in August 2018 awarded WMP A$50 million,” the website reports.

“We can’t do it for free,” says Simmons. “We need donor support to make it work. We don’t expect low-income countries to pay.”

WMP held talks with the Port Moresby Council in Papua New Guinea, but they didn’t progress when it was decided other health issues were more pressing.

Simmons says a big step towards more eradication efforts will come when the United Nations health system accepts the process.

“The World Health Organisation is working on what’s called a ‘recommendation,’ which is a sort of formal position from WHO on the method to member countries,” he says.” So the intention that the development banks and UN agencies would then be able to support the intervention.”