An experiment involving bacteria-infected mosquitoes helped decrease dengue cases by 77% in an Indonesian city.
Dengue fever is a mosquito-borne disease that causes 390 million infections per year. The majority of the cases occur in Asia. Countries such as India, Indonesia, Maldives, Sri Lanka, and Thailand are highly endemic for dengue. The rapidly increasing cases pose a threat to a country’s healthcare system and economic stability. Therefore, controlling the spread of infections is of great concern for researchers. However, current vector control methods of using insecticides and environmental methods have failed to control the disease. Now, a large-scale clinical trial has demonstrated the effectiveness of a new insect-control method.
Sponsored by the World Mosquito Program, the study introduced Wolbachia-infected mosquitoes over the Indonesian city of Yogyakarta. The team of researchers aimed to test whether the introduction of these modified mosquitoes into the local Aedes aegypti population would reduce the cases of dengue amongst the city residents. Aedes aegypti is a vector for several tropical diseases, including dengue.
Wolbachia pipientis is a bacteria commonly found within many insect species and can inhibit viral replication. However, it does not occur naturally in the A. aegypti population of mosquitoes. Therefore, researchers planned to introduce Wolbachia-infected mosquitoes in endemic areas with A. aegypti mosquitoes. They released the mosquitoes over a period of nine months. Once released, they bred with the wild mosquitoes. Thus, resulting in an increasing number of bacteria-infected mosquitoes.
77% Reduction in Cases
The randomized clinical trial assigned 12 geographical areas within Yogyakarta to receive the bacteria-infected A. aegypti mosquitoes. Whereas the other 12 areas continued to practice local vector-control measures. The trial then recruited around 8,000 participants aged 3-45 years; half of whom belonged to the control group and the other half belonged to the intervention cluster. The patients had all presented to local clinics with acute undifferentiated fever. They then underwent laboratory testing for the dengue virus.
According to the results published in the New England Journal of Medicine, dengue cases in the intervention cluster decreased by 77%. Moreover, there was an 86% reduction in hospitalization in the Wolbachia-treated areas. The high efficacy of the method was observed for all four dengue viral strains.
The trial is a significant step in finding a safe and effective method for reducing the incidence of dengue. Unlike other methods, Wolbachia is long-lasting and self-sustainable.
Utarini, Adi, et al. “Efficacy of Wolbachia-Infected Mosquito Deployments for the Control of Dengue.” New England Journal of Medicine, vol. 384, no. 23, 2021, pp. 2177–2186., doi:10.1056/nejmoa2030243.