Competing interests: The authors have declared that no competing interests exist.
The developing Pacific Island Countries and Territories (PICTs) are under increasing threat from both acute and chronic diseases ranging from HIV/AIDS to obesity. In addition, people residing in PICTs are highly vulnerable to environmental impacts from the sea level rise and extreme weather events associated with global warming. Ciguatera is a prevalent tropical and subtropical disease that has been an under-appreciated cause of acute and chronic disease in island communities and might be increasing in incidence due to increasing vulnerabilities (i.e. poverty, global warming, eutrophication) in these populations –.
Ciguatera is caused by the consumption of coral reef fish contaminated by ciguatoxin and related toxins from dinoflagellates (microalgae) and cyanobacteria , . The ciguatoxin bioaccumulates up the food web, either directly from incidental uptake by herbivorous fish or indirectly by carnivorous fish . After the consumption of coral reef fish contaminated with ciguatoxin, people experience potentially severe acute neurologic, gastrointestinal and cardiac symptoms as well as, in some cases, chronic neurologic symptoms lasting weeks to months , . Ciguatera occurs globally, in coastal tropical waters, and is particularly prevalent across the PICTs. Cases of ciguatera have also been reported in temperate regions of the world due to travel and coral reef fish export. Ciguatera poisoning is often under-diagnosed and under-reported, with only 2 to 10% of cases reported to health authorities (Friedman et al 2008). Estimates of the incidence of ciguatera in Oceania have ranged from 0.5/10,000/year in Hawaii to 5,850/10,000/year in French Polynesia . Fish is the staple protein source in many PICT communities, with many islands in the region suffering ongoing outbreaks of ciguatera leading to potentially significant impacts on large portions of the population of small island communities when toxic fish are consumed .
Dinoflagellates of the genera Gambierdiscus, that grow epiphytically on macro- and turf-algae on coral reefs, produce the ciguatoxins predominantly responsible for the disease known as ciguatera. Coral reef damage, or when algal growth is not controlled by herbivorous fish, provide increased potential habitat for Gambierdiscus growth that might increase the risk of ciguatera . Despite extensive research, we know little about the ecology and the environmental factors that cause the blooms of the ciguatera caustive organisms, nor do we understand the role (if any) of other dinoflagellate genera including Ostreopsis (palytoxin producers) and Prorocentrum (okadaic acid and dinophysistoxins producers) or marine cyanobacteria . Presently, ciguatoxin can only be detected in fish and Gambierdiscus in specialized labs, and diagnosis in humans is based almost exclusively on symptoms associated with the recent consumption of a potential ciguateric fish; factors that hamper its effective management and highlight important research needs , .
A number of factors have been associated with ciguatera cases and the presence of ciguatoxic dinoflagellates. Military activities causing coral reef damage in the Pacific, including from World War II, and nuclear test explosion programs, have been linked with outbreaks and changing incidence of ciguatera in some locations . The prevalence of ciguatera in the South Pacific increases dramatically where average sea surface temperatures are at least 28 to 29°C . Elevated sea surface temperatures associated with global warming are believed to already be exacerbating the extent and the range of ciguatera , . Reportedly, ciguatera occurrences are most prevalent in the warmest regions of the Caribbean, and all indigenous ciguatera cases have occurred where annual average temperatures are >25°C . Nutrient enrichment and warming sea surface temperatures have been shown to stimulate Gambierdiscus growth which results in higher cell densities . Also, benthic dinoflagellate species, including those of the genera Gambi