Ciguatera fish poisoning and climate change: analysis of national poison center data in the United States 2001-2011 Open Access
Gingold, Daniel Benjamin (2013)
Abstract
Ciguatera fish poisoning (CFP) is the world's most common seafood-toxin disease. CFP occurs when humans consume fish that have fed on ciguatera toxin-producing organisms, and is characterized by acute gastrointestinal upset followed by neurological symptoms such as numbness, weakness, and disruption of temperature sensation. Recent studies have demonstrated a relationship between CFP incidence and warmer sea surface temperatures (SST). Also, increased severe storm frequency may create more suitable habitat for ciguatoxic organisms. Climate change is expected to affect SST and storm frequency in the Caribbean, and may cause an increase in CFP prevalence and expansion beyond its current tropical range.
The purpose of this hypothesis-generating ecological time-series study was to determine if CFP incidence is associated with periods of warmer SST and increased storm frequency in the Caribbean over the last decade to inform predictions regarding climate change and CFP.
1,272 CFP-related calls to US poison control centers between 2001-2011 were identified from the National Poison Data System and analyzed using descriptive analysis and Poisson regression. Results showed an independent association between monthly CFP calls and warmer SST and tropical storm frequency, using fishing yields as an offset. The optimal lag period for SST was between 5 and 16 months; the variable selected links current monthly CFP calls to the peak August SST of the previous year. The optimal lag period for storms was 18 months. The rate ratio for an increase in storms by one per month was 1.113 (95% CI [1.03, 1.234]), and the rate ratio of a one-degree increase in SST temperature was 1.612 (95% CI [1.167, 2.243]).
These estimates imply that if the maximum Caribbean SST increases by 2.5°C as projected, and storm frequency increases by 10% from 2001-2011 levels, approximately 239 additional calls per year can be expected (95% CI [49.5, 665.9]), a two- to four-fold increase.
Using CFP calls as a marker of CFP incidence, these results support the hypothesis that CFP incidence is positively associated with warming SST and increased tropical storm frequency, and should inform adaptation measures to limit the potential public health impacts of unmitigated climate change.
Table of Contents
Chapter I: Literature Review......................................................................1
Chapter II: Manuscript.............................................................................16
Title, Authors, Abstract............................................................................16
Introduction...........................................................................................18
Climate Change and Public Health
Ciguatera Toxin Production
Ciguatoxin in Fish
Ecology of Ciguatera
Epidemiology of Ciguatera
Ciguatoxin Pharmacology
Ciguatoxin Detection
CFP Treatment
Ciguatera and Climate Change
Methods................................................................................................19
Ciguatera Cases Data
Sea Surface Temperature (SST) Data
Caribbean SST Anomaly Index Data
Severe Tropical Storms Data
Fishing Yields Data
Lagged Variables
Analysis Methods
Results................................................................................................. 25
Descriptive Analysis of Ciguatera Calls
Descriptive Analysis of Regression Variables
Poisson Regression Analysis of the Multivariate Model
Discussion............................................................................................. 31
Summary
Comparison of Results to Literature
Limitations
Public Health Impacts
Conclusions
References............................................................................................ 40
Tables.................................................................................................. 43
Table 1: Descriptive statistics of ciguatera call variables
Table 2a: Frequency of clinical effects for all calls
Table 2b: Frequency of selected clinical effects
Table 3a: Frequency of therapies for all calls
Table 3b: Frequency of selected therapies
Table 4: Descriptive statistics for regression analysis variables
Table 5: Individual variable regression results
Table 6: Rate ratios and excess CRP calls expected for hypothetical scenarios compared to 2001-2011 baseline
Table 7: Sensitivity of beta estimates to multivariate model selection
Figures................................................................................................. 49
Figure 1: Ciguatera fish poisoning distribution
Figure 2: Number of ciguatera calls by region and year, 2001-2011
Figure 3: Number and percent of calls by age group, 2001-2011
Figure 4: Total number of calls by month, 2001-2011
Figure 5: Recorded and imputed fishing yields
Figure 6: Yearly SST time series
Figure 7: August max SST and yearly storm total time series
Figure 8: August max SST and ciguatera calls by year
Figure 9: Regional SST, Poisson beta estimates by lag time
Figure 10: Warm SST extent, Poisson beta estimates by lag time
Figure 11: SST at parallels, Poisson beta estimates by lag time
Figure 12: Storm variables, Poisson beta estimates by lag time
Figure 13: Data analysis flowchart
Chapter III............................................................................................56
Summary..............................................................................................56
Public Health Implications........................................................................58
Possible Future Directions........................................................................60
Appendix: IRB Approval Letter..................................................................62
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