The association between ambient temperature and snakebites in Georgia, USA: a case-crossover study

Abstract

Background and aim: The World Health Organization has identified snakebite as a highest priority neglected tropical disease, yet there is a dearth of epidemiologic research on environmental risk factors, including outdoor temperature. Temperature may affect snakebites through human behavior or snake behavior; snakes are ectotherms, meaning outdoor temperatures influence their internal body temperature and thus their behavior. Here we investigate the relationship between short-term temperature and snakebites in Georgia, one of the most biodiverse US states in terms of herpetofauna. Methods: We acquired emergency department visit data for Georgia between January 1, 2014 and December 31, 2018. Visits for venomous and non-venomous snakebites were identified using diagnosis codes. For comparison, we also considered visits for non-snake (e.g. insects, spiders, scorpions) envenomation. Daily meteorology from the Daymet 1km product was linked to patient residential ZIP codes. We applied a case-crossover design to estimate associations with maximum temperature. Results: During the five-year study period, there were 2,785 visits for venomous snakebites, 825 visits for non-venomous bites and 48,248 visits for non-snake envenomation. Across the entire period, a one-degree Celsius increase in same-day maximum temperature was associated with a 6.2% (95%CI: 4.0-8.5) increase in the odds of venomous snakebite and a 7.4% (95%CI: 3.5-11.4) increase in non-venomous snakebite. Associations were most robust in the spring and fall, particularly for venomous snakebites. We also observed a positive and significant association for non-snake envenomation, albeit slightly weaker and more consistent across seasons compared to those for snakebites. Conclusions: Our study indicates an association between outdoor temperature and snakebites in Georgia. The results suggest that climate change could alter snakebite patterns in the future; however, impacts are likely to be dependent on the local climate and snake ecology (amongst other factors). Keywords: temperature, heat, morbidity, snake, climate change, one health, planetary health