Non-Communicable Diseases Caused by Ingestion of Toxic Marine Finfish and Shellfish and Strategies of Control

In tropical areas of the world many marine organisms that are perfectly safe to eat may at certain times accumulate toxins that cause intoxication when ingested by humans. Two groups of marine species, finfish and shellfish, are examples of these poisonous organisms. In this paper, we discuss the effects of toxins that accumulate in a wide variety of finfish and shellfish species.

Ciguatoxin is a well-known poison from large carnivorous fish and has been documented to occur in the Philippines, although accounts of intoxication mostly refer to other islands in the Pacific such as Fiji. Our friend and research colleague, Dr. Takeshi Yasumoto, identified the causative agent in the Fiji ciguatoxin outbreak as Gambierdiscus toxicus, which killed one person out of 9,255 victims. These dinoflagellates adhere to corals and seaweeds and are fed upon by herbivorous fish which are in turn fed upon by large carnivorous fish and biomagnified through the food chain. Ciguatoxin is odorless and heat resistant so it cannot be destroyed by conventional heating. Ciguatoxin poisoning is common in the Pacific and the Caribbean, and caused by a number of unrelated fish families but especially in the carnivorous species such as Lutjanus bohar, Sphyraena spp., Epinephelus fuscoguttatus and Lethrinus variegatus.

Harmful algal blooms commonly referred to as “red tides”, have harmful effects on sea life and cause mass mortalities in fish, invertebrates, birds and mammals. When toxic species are in bloom, the toxins are carried to the food chain and into humans via finfish or shellfish resulting in gastrointestinal disorders, neurological damage and even death. Toxic dinoflagellate blooms for example by Pyrodinium bahamense var. compressum blooms can cause Paralytic Shellfish Poisoning (PSP) are a natural phenomenon, but in the past two decades, their public health and economic impacts appear to have increased in frequency, intensity and geographic distribution. 

We also discuss here the toxins tetrodotoxin, saxitoxin and palytoxin found in five species of coral reef crabs belonging to the family Xanthidae. The highly poisonous five crab species (7-10 cm in carapace width) are Zosimus aeneus, Atergatis jloridus, Lophozozymus pictor, Demania alcalai (=D. cu/tripes), D. toxica or D. reynaudii and are common in our coral reefs. They are colourful and with distinctive markings and likely to be picked up by reef gleaners who do not know their poisonous nature. Some of the recorded five fatalities from ingestion of poisonous crabs came from land areas far from the sea. Not much is known about how these crabs get their poisons but it is hypothesized to be coming from their food. In our survey of coral reefs, we have recognized three kinds of crabs (a) highly poisonous, i.e, those that accumulate highly lethal toxins killing white mice within 30 minutes to one hour after injection, (b) mildly poisonous ( c) not poisonous

There is a need for an educational campaign including seminars in coastal municipalities and barangays informing people which crab species should not be consumed. Posters showing the poisonous species should be posted in strategic places. Medical personnel also need information about toxic crabs and poisonous fishes. Medical services to victims of these NCDs especially in rural areas should be improved/provided. The public should be informed that caution should be exercised before consuming large carnivorous finfish species. Viscera of large fish should not be eaten or given to pets. More research should be done to determine the prevalence of fish and shellfish poisoning in the Philippines. Development of cost-effective toxins (e.g. Paralytic Shellfish Toxins and Ciguatoxin) detection methods, for wider and effective diagnosis and management should be pursued.

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