# Modeling the potential distribution of Wesselsbron, Sindbis, and Middelburg viruses and their vectors in Africa under future climatic and land-use changes

## TL;DR

This study maps the future spread of three African arboviruses and their mosquitoes under climate and land-use changes, highlighting risks for human and animal outbreaks.

## Contribution

The study provides novel ecological risk maps for Wesselsbron, Sindbis, and Middelburg viruses and their vectors under future climate and land-use scenarios in Africa.

## Key findings

- High ecological suitability for five mosquito vectors is predicted in Equatorial and Southern Africa, with future hotspots emerging in Southern and Eastern regions.
- Changing precipitation patterns, urbanization, and climate are key drivers of vector and arbovirus geographic expansion.
- Ecological risk for arbovirus presence may shift from rural to urban areas with future ecological changes.

## Abstract

Outbreaks of zoonotic arboviruses originating in Africa occur amidst complex ecological changes and are increasingly emerging as important neglected tropical diseases. Despite sporadic epizootics and human cases of Wesselsbron virus (WSLV), Sindbis virus (SINV), and Middelburg virus (MIDV) in Africa, knowledge of associated risks remains insufficient for prevention.

We developed species distribution models for the three viruses alongside five key vectors, Aedes circumluteolus and Aedes mcintoshi for WSLV; Culex univittatus and Culex pipiens for SINV; and Mansonia africana and Aedes mcintoshi for MIDV that indicate areas with ecological suitability for the arboviruses in Africa. We integrated virus and mosquito species occurrence data with climate and land-use data for current (2015) and future (2021 – 2040) scenarios under two shared socioeconomic pathways of emission and climate projections. We applied the Maxent algorithm and evaluated over 100 candidate models per species, selecting those with above-random predictive performance based on high mean Area Under the Curve ratios (Range = 1.45 – 1.88).

Our models revealed high ecological suitability for the five mosquitoes in Equatorial and Southern Africa and predict emerging ecologically suitable hotspots for arboviral presence in Southern and Eastern regions, with potential future expansion into North and West Africa. Changing patterns in precipitation, especially precipitation in dry and warm seasons, urbanization, human population, livestock density, and climate change exacerbated the geographic expansion of vectors and ecological risk for arbovirus presence. While the ecological risk to arbovirus presence was currently higher in rural areas, our projections indicated a potential future shift towards urban areas.

Our study describes how ecological changes are shaping current and future ecological risk of neglected arboviral diseases in Africa and provides spatial maps to aid intersectoral targeted surveillance and vector control as part of early-warning systems.

Mosquito-borne arboviral diseases are a global health concern, particularly in Africa, where rich biodiversity and tropical climates favour vector breeding and virus emergence. Wesselsbron virus (WSLV), Sindbis virus (SINV), and Middelburg virus (MIDV) were first detected in Africa and have the potential to cause human and animal outbreaks, yet this risk has not been mapped. Our study sought to describe the role of climatic and land-use changes in the geographical distribution of the viruses and five suspected vectors. We developed species distribution models based on the species’ known occurrence, current and future climatic and land-use conditions. We mapped areas that are ecologically suitable for vector and arbovirus presence, highlighting potential human exposure. Key predictors of suitable habitats for the vectors were precipitation during dry and warm seasons, urbanization, and human and livestock presence. Notably, ecological risk for arboviral presence may be higher in rural areas, but with changes in ecology and land use, it could increase even in urban areas. Our findings reveal pronounced spatial heterogeneity and projected shifts in vector and arbovirus presence given ecological changes. In settings where the evidence for vector-host-virus ecology is underdeveloped, our ecological risk maps can indicate areas that could be targeted for vector control and intersectoral surveillance to strengthen early warning.