Evaluating the risk of ciguatera fish poisoning from reef fish in Hawai'i : Development of ELISA applications for the detection of ciguatoxin

Thesis (Ph.D.)--University of Hawaii at Manoa, 2008.Harmful algal blooms (HABs) are associated with several acute and chronic diseases in humans worldwide, which are characterized by gastrointestinal, neurological, and/or cardiovascular disturbances. Ciguatera fish poisoning, the most commonly reported marine toxin disease in the world, is the primary and most important human health manifestation of HAB and results from the consumption of fish containing high levels of ciguatoxins (CTXs), a family of complex, lipid-soluble compounds produced by the benthic marine dinoflagellate, Gambierdiscus toxicus.Quantitative, reliable methods to detect ciguatoxins in fish tissue are not widely accessible, thus rendering the detection of CTX in fish destined for human consumption a serious public health concern. This dissertation addresses an important food safety issue by developing and validating a sensitive and specific enzyme linked immunoassay (ELISA) capable of detecting picogram quantities of ciguatoxin in fish flesh. Development of the assay represents the first ELISA for detecting ciguatoxin using chicken antibody (IgY) as an immunoanalytic tool, and further establishes a relatively rapid, reliable method for screening large quantities of fish.The results of testing over 300 fish commonly implicated in ciguatera fish poisoning, specifically two species of amberjacks (kahala) and the blue spotted grouper (roi) using both the ELISA and a secondary bioassay to validate results leads to the following conclusions: (a) the ELISA is a valid screening tool for evaluation of presence or absence of ciguatoxin in fish tissues with reasonable sensitivity and specificity; (b) the fish farmed in open ocean aquaculture cages in Hawai'i are not likely to be susceptible to ciguatoxin bioaccumulation despite the discovery of G. toxicus in or on the cages; (c) CTX is present in three fish species commonly implicated in ciguatera fish poisoning at overall rates lower than previously reported; and (d) the prevalence of ciguatoxin in wild-caught fish cannot reliably be correlated to the size of the fish or the depth at which it was caught. This dissertation also demonstrates that the antibody used in assay development is reactive with purified ciguatoxin and provides evidence that the AB epitope of the CTX molecule is active at the sodium channel in neuroblastoma cells.Includes bibliographical references (leaves 115-131).Also available by subscription via World Wide Web131 leaves, bound 29 c