According to a study, an outbreak of ciguatera poisoning from contaminated fish affected 19 people on a ship in Australia.

The food poisoning outbreak was reported to the Central Queensland Public Health Unit in December 2021.

A bulk carrier sailing from Higashiharima, Japan, to Gladstone, Australia, reported an incident of sudden illness, with 19 of 20 sailors on board having a combination of gastrointestinal and neurological symptoms.

All 20 sailors consumed a self-caught barracuda and squid prepared by the ship’s cook the day before. Leftover samples of the fish and squid were sent for testing. According to the study published in the journal Communicable Diseases Intelligence, the barracuda sample contained ciguatoxins.

Mainly mild cases
Most crew members who fitted the definition of a probable case complained of sudden onset of nausea, vomiting, diarrhea, abdominal pain, fatigue, muscle pains and aches and a variety of neurological symptoms including paraesthesia, ataxia, and a metallic taste in the mouth. They were males from the Philippines, aged 26 to 54 years old. No samples of the symptomatic individuals’ stool or vomit were available. Paraesthesia describes a pricking, burning, tingling or numbing sensation. Ataxia can affect coordination and balance.

Most cases were mild and did not require emergency department review or hospitalization. For five sailors who ate the meal, inpatient medical management was needed. One person had an underlying acute kidney injury resulting from dehydration, which led to three days’ admission for intravenous therapy but a subsequent full recovery.

“We suggest that the combination of gastrointestinal symptoms and paraesthesia in at least 40 percent of the affected consumers of ocean fish could be used to classify a foodborne outbreak in the eastern seaboard of Australia as highly likely due to Ciguatera poisoning,” said scientists.

The crew could not access testing facilities to check potential food contamination with ciguatoxin. The previously available commercial CiguaCheck test kits were proven to be unreliable and operator-dependent. Portable smartphone-controlled amperometric or electrochemical immunosensors show potential, but the multi-step sample extraction and purification process is complicated, according to the study.

Raising awareness of Ciguatera
Given the route of the bulk carrier sailing from Higashiharima to Gladstone, it could have passed through the Marshall Islands, which is classified as a prohibited fish supply region by the Australian Seafood Handling Guidelines.

Based on current literature, there is a correlation between the clinical picture of Ciguatera poisoning and the area where contaminated fish is caught. For example, Pacific region Ciguatera poisoning tends to trigger more neurological disorders, and Caribbean region Ciguatera poisoning leads to a greater rate of gastrointestinal symptoms, according to the study.

Researchers said efforts should be directed toward health promotion initiatives, including raising awareness among the general public, marine personnel, and physicians. They also suggested establishing policies imposing limits on species of fish and fishing regions.

Ciguatoxins are not destroyed by cooking, freezing, or canning processes. Symptoms appear within hours of consuming contaminated food, lasting a few days. They include vomiting, diarrhea, muscle weakness, and dizziness. Some people suffer from itching, tingling, or blurred vision; others find cold things hot and hot items cold.

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