Scaled deployment of Wolbachia to protect the community from dengue and other Aedes transmitted arboviruses

Abstract

Background: A number of new technologies are under development for the control of mosquito transmitted viruses, such as dengue, chikungunya and Zika that all require the release of modified mosquitoes into the environment. None of these technologies has been able to demonstrate evidence that they can be implemented at a scale beyond small pilots. Here we report the first successful citywide scaled deployment of Wolbachia in the northern Australian city of Townsville. Methods: The wMel strain of Wolbachia was backcrossed into a local Aedes aegypti genotype and mass reared mosquitoes were deployed as eggs using mosquito release containers (MRCs). In initial stages these releases were undertaken by program staff but in later stages this was replaced by direct community release including the development of a school program that saw children undertake releases. Mosquito monitoring was undertaken with Biogents Sentinel (BGS) traps and individual mosquitoes were screened for the presence of Wolbachia with a Taqman qPCR or LAMP diagnostic assay. Dengue case notifications from Queensland Health Communicable Disease Branch were used to track dengue cases in the city before and after release. Results: Wolbachia was successfully established into local Ae. aegypti mosquitoes across 66 km2 in four stages over 28 months with full community support. A feature of the program was the development of a scaled approach to community engagement. Wolbachia frequencies have remained stable since deployment and to date no local dengue transmission has been confirmed in any area of Townsville after Wolbachia has established, despite local transmission events every year for the prior 13 years and an epidemiological context of increasing imported cases. Conclusion: Deployment of Wolbachia into Ae. aegypti populations can be readily scaled to areas of ~60km2 quickly and cost effectively and appears in this context to be effective at stopping local dengue transmission

Reflections from an old Queenslander: can rear and release strategies be the next great era of vector control?

“…In addition to traditional community information sessions, developing a community-led 'project advisory committee, community reference group, etc.' is critical [42]. These groups disseminate information to key community and governmental leaders, and serve as a source of information from the public-a twoway communication strategy.…”

“…Using the public to literally become the rear and release machine, by hatching egg strips and rearing larvae in disposable paper containers, helped WMP release and establish Wolbachia-infected Ae. aegypti at scale in Queensland [42]. Finally, the released material must be fit relative to the wild population.…”

Persistent deleterious effects of a deleterious Wolbachia infection

“…There is increasing interest in using Wolbachia bacterial infections for suppressing dengue transmission by mosquitoes, with field releases aimed at both replacing existing natural mosquito populations with those infected by Wolbachia [1,2] and suppressing these populations through sterility induced by Wolbachia-infected males [3]. Replacement releases can be effective because the presence of Wolbachia in mosquitoes reduces transmission of arboviruses [4][5][6].…”

Evidence for natural hybridisation and novel Wolbachia strain superinfections in the Anopheles gambiae complex from Guinea

“…aegypti populations in Cairns, Australia [13] was followed by further evidence of strong inhibitory effects on arboviruses from field populations [14]. Further follow up studies in Townsville, Australia [15] and Kuala Lumpur, Malaysia [16] have now shown that Wolbachia frequencies have remained stable since initial releases and there is a reduction in human dengue incidence in the release sites.…”