A systematic review of variables associated with snakebite risk in spatial and temporal analyses

Background: Snakebite is a priority neglected tropical disease, but incidence data are lacking; current estimates rely upon incomplete health facility reports or ad hoc surveys. Spatial analysis methods harness statistical associations between case incidence and spatially varying factors to improve estimates. This systematic review aimed to identify variables associated with snakebite risk in spatial and temporal analyses for inclusion in geospatial studies to improve risk estimation accuracy.

Methods: We searched MEDLINE, Global Health, PubMed and Web of Science in January 2023 for studies published since 1980 assessing snakebite outcomes and spatially varying factors at the setting level. Study quality was assessed using an adapted Joanna Briggs Institute tool. The results are presented by narrative synthesis.

Results: Thirty-five studies were eligible; the majority were from Central and South America (18), then Asia (11). Climate and environment were most frequently assessed, with temperature, humidity and tree cover predominantly positively associated with snakebite risk, drought negatively associated and altitude negative/mixed. Crop and livestock variables mostly showed positive associations; population density and urban residence overwhelmingly displayed negative associations.

Conclusions: This review identifies key variables that should be considered in future snakebite risk research. Limitations include low research availability from the highest risk regions. There is an evident need for greater research into snakebite risk variation, particularly in sub-Saharan Africa.