Ciguatera fish poisoning in St. Thomas, U.S. Virgin Islands: Trends since 1980

Introduction. Ciguatera fish poisoning is the most common marine food poisoning globally, affecting many tropical and sub-tropical countries. Our objective was to estimate the incidence of ciguatera in St. Thomas and assess possible explanations for the change over time. Methods We performed a random digit dial telephone survey in 2010 and 2011. Incidence was estimated based on the number of respondents with ciguatera illness in the past five years and weighted for age, sex, and education. A second estimate was based emergency department (ED) data and the percent visiting the ED for their most recent episode. Data on seawater temperature, fish landings, and other environmental variables in St. Thomas were obtained from external sources to explore their impact on incidence. Results The incidence of ciguatera in adults was 12 per 1000 (95% confidence interval (CI)=10-21). The estimate based on ED visits was 6 per 1000 (95% CI=5-8). We found a significant negative correlation between seawater temperature and annual ciguatera incidence (R2=0.53, p=0.0015) for 16 years between 1971 and 2011. Fish landings remained stable over the study period. Conclusion Our evidence indicates that ciguatera incidence in St. Thomas has declined since 1980. Past studies have suggested that ciguatera would increase with higher seawater temperatures associated with climate change, but this is not consistent with our findings. It is unclear whether St. Thomas has reached an upper temperature threshold limiting the amount of ciguatera or if another factor is causing the decline. Further study is needed to characterize factors that influence ciguatera.