World Mosquito Program (WMP), 2023

Implementing Partners: WMP, MSF, Save the Children, USAID, DFAT, Welcome, Bill & Melinda Gates Foundation

Published In: COP28 Prospectus of Climate-Health Solutions, 2023

Using laboratory transfer of Wolbachia bacteria into Aedes aegypti mosquito populations to prevent outbreaks of dengue virus in multiple cities around the world.

Context

Climate change is accelerating the global spread of Aedes aegypti, an invasive mosquito species that is primarily responsible for the transmission of dengue, chikungunya, Zika, and yellow fever. The WHO has declared dengue one of the top ten threats to global health – it annually infects approximately 400 million people and costs health systems worldwide $12 billion annually. Warmer temperatures significantly increase vector efficiency, transmission season and geographic suitability for dengue virus. By 2050, more than 6 billion people will live with the risk of dengue infection, and it is poised to become endemic in the United States, continental Europe, and northeastern Asia, if action is not taken to curb its spread.

Approach

The World Mosquito Program (WMP) has developed a safe, effective, cost-saving, and ecologically friendly method to reduce the transmission of dengue, chikungunya, Zika, and other mosquito-borne viruses. It involves transferring Wolbachia, a naturally occurring endosymbiotic bacteria already found in 50% of all insect species, into the cells of Aedes aegypti mosquitoes. Wolbachia bacteria competes with viruses and dramatically reduces the ability of viruses to replicate in their mosquito hosts. This subsequently limits transmission of the virus to humans.

Scientists infect mosquitoes with Wolbachia in a fairly simple manner. First, the bacteria is introduced into Aedes aegypti mosquito eggs. From these eggs, new mosquitoes are bred in a laboratory. The newborn male mosquitoes with Wolbachia are then released into the wild which mate with wild female mosquitoes. Eggs derived from these mosquito pairs do not hatch and as a result the number of Aedes aegypti mosquitoes decreases.

In terms of cost, the most cost effective mosquito releases have been conducted at a per person cost of $5-6, and the technology can achieve lower cost and greater scale through improvements in mosquito production technology and the development of more efficient release technologies (e.g., fixed-wing aircraft).  Since WMP began implementing its Wolbachia method in 2007, the organization has had strong donor support and has effectively leveraged local academic partnerships which have enabled implementation of the Wolbachia method. The Wolbachia technology was developed with funding from Wellcome, the Bill & Melinda Gates Foundation, and other major philanthropic donors.

Impact & Next steps

The Wolbachia method is a highly successful methodology and implementation model. WMP conducted a cluster randomized controlled trial (RCT) within a 26 km2 area of Yogyakarta, Indonesia to measure the efficacy of the Wolbachia method. The peer reviewed results of the trial showed that Wolbachia deployments reduced dengue incidences by 77% and dengue-related hospitalizations by 86%. Preliminary analysis of Wolbachia deployments across an urban population of 3.3 million people in the cities of Bello, Medellin, and Itagui, Colombia demonstrated sustained dengue suppression of 95-97%.

Currently, WMP’s Wolbachia technology is estimated to protect 10 million people across 30 cities in 11 countries and is estimated to have prevented more than 300,000 dengue cases and 20,000 hospitalizations. It is projected to prevent another 1-3 million dengue cases over the next decade in the communities where releases have already been completed.

Cost effectiveness analyses reviewing WMP’s Wolbachia model have indicated that the method is highly cost effective. According to a 2020 study, when deployed in high density urban areas, Wolbachia has shown cost effectiveness below $1500 per disability adjusted life year (DALY) averted. Economic modeling for Indonesia indicates that Wolbachia would pay back two to three times the initial investment within 10 years through averted medical costs and gains in productivity. Similar modeling for Colombia indicates that Wolbachia would pay for itself within 5-10 years through savings in medical costs. In Brazil, Wolbachia releases are likely to return more than $45 for every dollar invested over a 20 year time horizon.

The positive results of the RCT study in Indonesia have also rapidly accelerated country interest in Wolbachia as an effective solution for rising dengue cases. WHO’s Neglected Tropical Diseases Program has committed to conducting regional workshops with dengue affected member states following the publication of its technical and operational guidance for Wolbachia, and WHO’s endorsement of the technology will signal to multilateral finance institutions that the technology is eligible for concessionary financing.