Outbreak linked to reef fish across multiple regions in Vanuatu

The Ministry of Health in Vanuatu has reported an outbreak of ciguatera poisoning across several regions in the island group. There have been 44 notifications with 2 people hospitalised. A facebook warning has been provided by the Ministry. It highlights the species of fish which may be the source of the outbreak.

The warning was posted on the Health Promotions Vanuatu Facebook page.

Reports on ciguatera poisoning are not uncommon in tropical regions.

An unusual case was recently highlighted in the Canary Islands where the toxin was identified in a fish of just 2 kg. The article suggested this may be one of the reasons why the diagnosis is either delayed or goes unrecognised.

Physicians are asked to consider ciguatera poisoning in anyone exhibiting gastrointestinal disturbances plus neurological symptoms (paraesthesia or unusual skin sensitivity) after a fish meal.

Read more: Small fish carrying ciguatera toxin detected in the Canary Islands

What is ciguatera poisoning?

Ciguatera is a special form of poisoning that occurs when the tropical reef fish you eat have ingested algal toxin. The toxic effects have been known for centuries but what is responsible for the poisoning has only been understood for the last 40 to 50 years.

An estimated 50,000 to 200,000 cases are reported annually. The real number is likely to be in the millions. High rates occur in French Polynesia and the Virgin Islands.

The case mortality rate is less than 1% but the effects of the poisoning may cause significant morbidity.

In 1774 Captain Cook and his crew experienced a bout of poisoning while visiting New Hebrides (now Vanuatu)!

How does ciguatera spread?

Ciguatera poisoning occurs in tropical regions where it is mostly related to coral reefs. It is believed that some aspect of reef damage is usually responsible – a cyclone, human or agricultural pollution or coral bleaching as is happening with climate change.

A much higher prevalence has been noted with ocean temperatures above 28C, also a feature of climate change.

It is thought the toxin is released by the environmental disturbance and then settles on the sea floor. It is then picked up by bottom feeding fish which are then part of the food chain.

Ultimately it is consumed by humans.

Ciguatera poisoning is likely underdiagnosed and underreported with fewer than 10% cases being reported.

Be careful if you are buying fresh fish from local fisherman to cook yourself. Suspect this toxin if there is any numbness of the hands or stinging sensation after skinning or filleting the fish.

Cooking does not destroy the toxin, and you can become seriously ill.

How to reduce your risk of exposure to the toxin

• Be aware of specific locations where ciguatera has been reported
• Avoid casseroles using fish cutlets
• Eat fish of less than 2-3 kg rather than portions of the larger pelagic fish
• Avoid the liver, roe and viscera of tropical fish
• Be aware of the link between environmental disturbances and ciguatera
• Do not consume moray eels
• Avoid: barracuda, chinaman fish, coral cod, coral trout, groper, paddy tail, red bass, red emperor, Spanish mackerel, spotted mackerel, trevally.

Ciguatera in Australia

Ciguatera poisoning is notifiable in Australia. About 150 cases are notified annually. This would be only a small percentage of actual cases.

Queensland Health provides a good overview of the condition in their guidelines for Public Health Units, which documents fish of concern.

Further information is also available on the SafeFish ciguatera resource page.