Study Discovers Promising Novel Method to Control Dengue: NEJM

Aedes aegypti mosquitoes are the primary vectors of dengue. Efforts to control A. aegypti populations with the use of insecticides or environmental management methods have not been effective in controlling dengue as a public health problem in most countries. Wolbachia pipientis — a common, maternally inherited, obligate intracellular type of bacteria — infects many species of insects but does not occur naturally in A. aegypti. Stable transinfection of A. aegypti with some strains of Wolbachia confers resistance to disseminated infection by DENV and other arboviruses. Thus, the introgression of "virus-blocking" strains of Wolbachia into field populations of A. aegypti is an emerging dengue-control method.

Therefore, Dr Adi Utarini and her team conducted a study to assess the efficacy of deployments of A. aegypti mosquitoes infected with the wMel strain of Wolbachia in reducing the incidence of VCD in Yogyakarta, Indonesia.

In this cluster-randomization trial, the researchers randomly assigned 12 geographic clusters to receive deployments of wMel-infected A. aegypti (intervention clusters) and 12 clusters to receive no deployments (control clusters). All clusters practised local mosquito-control measures as usual. They used a test-negative design to assess the efficacy of the intervention. The researchers included a total of 8144 patients with acute undifferentiated fever who presented to local primary care clinics. Among 8144 patients, 3721 lived in intervention clusters, and 4423 lived in control clusters. They used laboratory testing to identify patients with virologically confirmed dengue (VCD) and those who were test-negative controls. The major outcome assessed was symptomatic VCD of any severity caused by any dengue virus serotype.

Key findings of the study were:

• Upon intention-to-treat analysis, the researchers noted that the VCD occurred in 67 of 2905 participants (2.3%) in the intervention clusters and 318 of 3401 (9.4%) in the control clusters (aggregate odds ratio for VCD, 0.23).
• They observed that the protective efficacy of the intervention was 77.1% against all four DENV serotypes and with the greatest confidence observed against DENV-2 and DENV-4 since these were the most prevalent serotypes.
• They found that the incidence of hospitalization for VCD was lower among participants who lived in intervention clusters (13 of 2905 participants [0.4%]) than among those who lived in control clusters (102 of 3401 [3.0%]) (protective efficacy, 86.2%).

The authors concluded, "Introgression of wMel into A. aegypti populations was effective in reducing the incidence of symptomatic dengue and resulted in fewer hospitalizations for dengue among the participants."

For further information:

https://www.nejm.org/doi/full/10.1056/NEJMoa2030243