Vector Control Advisory Group
Independent evaluation of the public health value of innovative new tools, technologies and approaches for vector control is needed to enable WHO to provide evidence-based advice to Member States on whether their deployment is justified. This is essential to ensure that scarce resources available for disease control are used to maximum impact. In order to assist WHO in developing public health policy on new tools, the Vector Control Advisory Group (VCAG) assesses the public health value of new interventions and provides guidance on developing the evidence base required to inform such assessments.
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Reduced pathogen transmission by a microorganism

Wolbachia is a symbiotic bacterium that occurs naturally in many insects. Although Wolbachia is not found naturally in Ae. aegypti, it has been successfully transferred into the mosquito and has been found to reduce transmission of a range of viruses including dengue, Zika, chikungunya and yellow fever. Wolbachia also confers reproductive advantages to female mosquitoes infected with Wolbachia over uninfected females through cytoplasmic incompatibility. This means that when male mosquitoes infected with Wolbachia mate with females that are not infected, their eggs do not hatch. Conversely, female mosquitoes infected with Wolbachia can mate with either infected or uninfected males and produce almost 100% infected offspring, giving infected females a fitness advantage and assisting the spread of Wolbachia into wild mosquito populations.

 

Wolbachia-establishment
World Mosquito Program (www.worldmosquitoprogram.org)
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How the intervention works: An example of an intervention being evaluated under this intervention class is the introduction of Wolbachia bacteria into populations of Ae. aegypti mosquitoes. The intervention involves time-limited field releases of Ae. aegypti mosquitoes infected with Wolbachia, which breed with wild mosquitoes, thus spreading Wolbachia among mosquito populations. Over time, the percentage of mosquitoes carrying Wolbachia increases, and Wolbachia continues to be passed from one generation of mosquitoes to the next, so that further releases are unnecessary. Ultimately the aim is that, almost all mosquitoes in a local area will contain Wolbachia and have a reduced ability to transmit viruses to people.

Disease(s) that may be reduced in prevalence or prevented: Aedes-borne arboviral diseases caused by dengue, chikungunya, Zika and yellow fever viruses.

Population(s) intended to be protected: Communities in areas in which Ae. aegypti is the predominant vector.

Status of review: A randomized cluster trial of the method is in progress in Yogyakarta, Indonesia. VCAG provided advice to the applicant on the trial design. The aim of the trial, which is estimated to be completed in 2020, is to provide epidemiological evidence of the extent of disease reduction due to the use of Wolbachia-infected mosquitoes.

Last update: 18 June 2020