Building a model for an effective vector control response to Aedes-borne arbovirus outbreaks in sub-Saharan Africa

(i) Global health need

The incidence of Aedes-borne diseases, including dengue, chikungunya, yellow fever and Zika, has increased dramatically over the last 50 years; over half of the world's population now live in an area at risk of one or more of these infections (Bhatt et al., 2013). The global increase in trade and travel, climate change and urbanization are major drivers behind this trend, leaving cities in the tropics particularly vulnerable to outbreaks.

Countries rely on vector to control to limit disease spread, due to the lack of effective vaccines or curative treatment for most arboviral infections. However, established interventions such as larval source management and reactive outbreak control via insecticide spraying show little evidence of impact on disease transmission (Bowman et al., 2016). Alternative approaches e.g. Wolbachia symbionts, show promise but remain years away from implementation in resource-poor settings.

(ii) Current knowledge gaps

There is an urgent need for novel vector control tools that can be utilised at the community level and deployed rapidly in response to outbreak. Recent studies have established the potential of two simple interventions; volatile spatial pyrethroid emanators ('emanators') and targeted indoor residual spraying (TIRS) (Buhagiar et al., 2017; Dunbar et al., 2019).

In West Africa, the burden of malaria and filarial infections have long dominated the vector control landscape. Hence, until recently little attention had been paid to arboviral disease in this region; entomological insight and epidemiological data remain sparse in comparison with Asia and Latin America.

This project will address some of the key knowledge gaps, exploring the potential of emanators or TIRS for sustainable effective vector control in West Africa. The fieldwork will be conducted in Yaoundé, Cameroon, and is intended to act as a model for intervention applicability in other locations in sub-Saharan Africa.

(iii) Study objectives

1. Identify current vector control practices in Yaoundé and evidence of impact.
2. Characterise the distribution and peridomestic behaviour of adult Aedes spp. in Yaoundé.
3. Identify community perceptions and practices relating to arbovirus transmission.
4. Pilot study of efficacy of potential vector control interventions against entomological outcomes.

(iv) Study design/methodology

This is a mixed-methods study. The current vector control situation in Yaoundé will be investigated through review of relevant policy documents and reports. Interviews will be conducted with the National Malaria Control Program (NMCP) and other relevant actors, identified through stakeholder mapping alongside the Cameroon Technical Vector Control Advisory Group (TVCAG).

Entomological surveillance will be conducted to explore the biology and behaviour of Aedes spp. across Yaoundé, using a novel spatially explicit sampling scheme to identify sampling sites; demographic information and housing characteristics will also be assessed and analysed to determine any relationship between these factors and Aedes density.

Social science work, in the form of KAP surveys and focus group discussions (FGDs) with community members, will be used to evaluate perceptions and practices regarding arboviral transmission, and to explore the acceptability of novel vector control tools.

A small-scale household randomized controlled trial, based on the findings above, will be conducted to evaluate the impact of either TIRS or emanators on entomological outcomes. The acceptability of the intervention will be explored with community members in FGDs.