Vector diversity and malaria prevalence: global trends and local determinants

Identifying determinants of global infectious disease burden is a central goal of disease ecology. While it is widely accepted that host diversity structures parasite diversity and prevalence across large spatial scales, the influence of vector diversity on disease risk has rarely been examined despite the role of vectors as obligatory intermediate hosts for many parasites. Malaria, for instance, can be transmitted by over 70 species of mosquitoes, but the impact of this diversity on malaria risk remains unclear. Further, such relationships are likely dependent on the context in which disease transmission occurs, as arthropod life history and behavior are highly sensitive to environmental factors such as temperature. We studied the relationship between vector diversity, malaria prevalence, and environmental attributes using a unique dataset we curated by integrating several open-access sources. Globally, the association between vector species richness and malaria prevalence differed by latitude, indicating that this relationship is strongly dependent on underlying environmental conditions. Structural equation models further revealed different processes by which the environment impacts vector community assemblage and function, and subsequently disease prevalence, in different regions. In Africa, the environment exerted a top-down influence on disease through its role in shaping vector communities, whereas in Southeast Asia, disease prevalence is influenced by more complex interactions between the physical and socioeconomic environment (i.e., rainfall and GDP) and vector diversity across sites. This work highlights the key role of vector diversity in structuring disease distribution at large spatial scales and offers crucial insights to vector management and disease control. Significance statement The global health threat from persistent and emerging vector-borne diseases continues to increase and is exacerbated by rapid environmental and societal change. Predicting how disease burden will shift in response to these changes necessitates a clear understanding of existing determinants of disease risk. We focused on an underappreciated potential source of variation in disease burden – vector diversity – and its role in structuring global malaria distribution. Our work revealed that vector diversity influences malaria prevalence and that the strength and nature of this association strongly depend on local environmental context. Extending disease transmission theory, surveillance, and control to embrace heterogeneity in vector community structure and function across space and time is an asset in the fight against vector-borne diseases.