Cases of Marine Fish Poisoning
By Rafael D. Guerrero III
Some marine fish become poisonous after feeding on toxin-producing organisms.
With the frequent occurrence of red tide on Philippines waters, the public has become wary and discriminating in its choice of seafood. The red tide renders bivalves like mussels, oysters and clams in affected coastal areas unsafe for human consumption. Fishes are generally not problematic as long as people remove their gills and entails before they are cooked and eaten.
There are instances, however, when marine fish poisonings do occur and lead to sickness or even death. Cases of ciguatera, pufferfish poisoning and goby fish poisoning have occurred in the country.
Ciguatera is a disease caused by the eating of toxic fishes that inhabit like red snappers, groupers and eels become poisonous when they prey on plant-eating fishes like the surgeonfish (“labahita”). These have, in turn, eaten blue-green algae present in coral reefs producing the poisonous substance.
The symptoms of ciguatera are prickling of lips, tongue and throat; numbness, nausea and vomiting. The victim may also experience dryness of mouth, abdominal cramps and insomnia. While the death rate for the disease is usually low, recovery is slow and may take several months.
The poison causing ciguatera is known as ciguatoxin. Although there is no known antidote for the disease, the intravenous administration of mannitol reportedly alleviates symptoms. The disease is common in the South Pacific where the incidence is estimated to be as high as 500 cases per 100,000 inhabitants. The fatality rate is a low 0.1 percent.
In the Philippines, ciguatera was reported by the staff of research vessel conducting studies in the waters off Palawan. The internal organs of a barracuda (a carnivorous fish preying in coral reef fishes) were eaten by the afflicted researchers, who lived to tell their story. To avoid the disease, experts advise consumers to avoid eating the head and entrails of suspect fish.
Another type of marine fish poisoning similar to ciguatera is pufferfish or “butete” poisoning. This disease is common in the country. In November 1992, for example, at least two deaths were reported in Eastern Visayas.
In Japan, where the pufferfish is prepared as a delicacy known as “fugu” over 3,000 people have reportedly been poisoned in a period of more than 20 years with a mortality rate of 51 percent. Symptoms of the disease include lightheadedness, headache, nausea, vomiting, diarrhea, abdominal pain and weakness. These can appear 10 minutes to four hours after the pufferfish is eaten.
The pufferfish poison has been identified as tetrodotoxin, a toxin believed to be produced by bacteria which colonize the tissues of the fish. It is found in the liver, gonads, intestines, muscles, blood and skin. Like other fish poisoning causes, there is no antidote or cure to pufferfish poisoning. As a first aid measure, doctors recommend gastric lavage or elimination of the toxin in the stomach within three hours from ingestion.
A more common type of fish poisoning in the Philippines is scombroid or “pseudo-allergic” fish poisoning. This is caused by the eating of fish with dark meat that has been improperly handled and stored. Fishes like the mackerel and tunas are often implicated. When these fishes caught in the sea are roughly handled and poorly refrigerated, their flesh is decomposed by bacteria, which produce a toxin known as histamine.
Signs of scombroid fish poisoning appear 15 minutes to several hours after consumption of the affected fish. Victims experience facial flushing and sweating, abdominal cramps, diarrhea, nausea, headache and palpitation. Itching and appearance of hive-like skin lesions are also common. The patients are treated with emetics, cathartics and gastric lavage.
And finally, a rare but previously reported case of marine fish poisoning that killed four people in Cavite in March 1992 is goby fish poisoning. A species of goby or “biya”, known to science as Gobious criniger, has been documented to be toxic at certain months of the year. The toxin in the fish – known as saxitoxin – is the same poison found in the red tide-causing organism that makes green mussels or “tahong” toxic.
The goby is 3.2 to 9.2 centimeters long and has black spots on its body, tail, and dorsal fins. It is found in beaches at low tide and in crab holes at high tide. The skin, viscera and muscles of the fish contain the poison. Symptoms of goby fish poisoning are similar to those of pufferfish poisoning.