Ciguatera Fish Poisoning: Dinoflagellate dynamics, toxin formation, and economic impacts

Ciguatera is a complex clinical syndrome caused by the consumption of fish
contaminated with toxins produced by the benthic dinoflagellate Gambierdiscus toxicus. It is the
most common human illness associated with harmful algal blooms (HABs) and the one with the greatest public health and economic impact. Despite the frequency with which it occurs and the vast number of victims globally (50,000 annually), the restriction of the disease to tropical islands has resulted in minimal scientific attention, exacerbated by local reticence to mention the disease for fear of potential negative impacts on the tourist trade.  However, because of its presence, major reef fisheries around the globe are not available for commercialization and many island societies are unable to utilize their local fish as sources of much-needed protein. In addition, incidents of ciguatera have expanded beyond the geographic range of the syndrome with increased per capita consumption of seafood and growing interregional seafood trade.

The incidence, prevalence, and worldwide distribution of ciguatera appear to be increasing, paralleling a worldwide increase in HABs. This may be linked with degradation of reef environments due to both anthropogenic and natural environmental changes. Some argue that ciguatera may be one of our most sensitive indicators of environmental disturbance in tropical ecosystems. Given the rate at which we are modifying these systems, there is an urgent need to increase our understanding of this poorly studied syndrome and the algal species and environmental forcings that cause it in order to predict and minimize the risk of illness.

The specific aims of the research are to:
•    Assess the health effects and associated economic impacts from ciguatera exposure in the USVI;
•    Investigate the relationships between environmental factors and other stresses to coral reef systems in the USVI, the dynamics of toxic Gambierdiscus species, and associated cases of CFP in humans; and
•    Assess the ability of gambiertoxins from G. toxicus to activate signaling pathways regulating the expression of biotransformation enzymes in fish, providing an initial step in understanding the mechanisms by which gambiertoxins are converted to the more potent ciguatoxins.

The project findings will contribute to the development of long-term datasets and a predictive capability that will link fluctuations in the incidence of ciguatera to environmental forcings such as temperature changes, pollution, bleaching events, or storms that occur long before human illnesses begin to appear.  Furthermore, this project will also assess the processes by which the biotransformation of gambiertoxins to ciguatoxins occurs in fish, which is an important step in understanding the passage of these toxins in the coral reef food chain.

Relevant Publications

Anderson, D. M. and P. S. Lobel (1987) The continuing enigma of ciguatera.  Biological Bulletin 172: 89-107.

Holmes, M. J., Lewis, R. J., Poli, M. A., and Gillespie, N. C. (1991) Strain dependent production of ciguatoxin precursors (gambiertoxins) by Gambierdiscus toxicus (Dinophyceae) in culture.

Lewis, R. J. (2001) The changing face of ciguatera. Toxicon 39(1), 97-106

Lewis, R. J., and Holmes, M. J. (1993) Origin and transfer of toxins involved in ciguatera. Comp Biochem Physiol C 106(3), 615-628

Lobel, P. S., D. M. Anderson and M. Durand-Clement (1988) Assessment of ciguatera dinoflagellate populations:  sample variability and algal substrate selection.  Biological Bulletin 175: 94-101.