357 Climate Change and Snakebites in California, 1997 to 2017

Abstract

The global climate change effect on flora and fauna has been scientifically documented, but the effect of drought and precipitation changes on North American snakebites is unknown. This study's objective was to correlate snakebite incidence with weather and climate changes in California over 20 years. A retrospective analysis of all snakebite exposures reported to the Californian Poison Control System from 1997 to 2017. Demographics, morbidity, and envenomation variables were cohorted by caller zip code as a proxy for county-based incidence, and then correlated 6 separate databases containing: climate and weather data, air temperature, precipitation, population data, eco-regions, and land characteristics. These data were temporally and spatially aligned to provide aggregate incidence within land type, and adjusted for population to calculate incidence per million individuals. Time series modeling was performed using seasonal decomposition by Loess curve fitting. Dynamic linear lagged time series regression was used to develop predictive models between snakebite incidence and weather covariates. Multiple linear regression was used to explore how environmental and demographic variables in each county-year combination may have contributed to the incidence of envenomations. There were 5,365 reported snakebites during the study period, with a median age of 37 years (22 - 51) with 76% male (p < 0.001, 95% CI 76% to 78%). For patients between 20 - 30 years old, the male to female ratio was 5:1; 2:1 in all ages. Most envenomation outcomes were coded as minor (1363, 25%) or moderate (2607, 49%), with 3 deaths. Among the 3580 (67%) of reports with detailed treatment data, the most common intervention was FAB antibody (59%). Adjusted for population, the annualized incidence of snakebites did not significantly change during the study period (rho = -0.11, p = 0.65). The snakebite incidence per million people appeared to rise after a period of no drought and declined during periods of drought (r = -0.41, p-value < 0.01). Snakebite incidence decreased by 6 month prior drought (- 3.8% for each 10% increase in drought), and increased by 18 month prior precipitation (+ 3.9% for each 10% increase in precipitation). Weather patterns appear to have a significant and predictive effect on snakebites in California. Snakebite incidence decreased following drought, and increased after precipitation. Awareness of these trends may assist the public with seasonal snakebite risk assessment, and medical providers with preparation and appropriate resource allocations.