Fighting ciguatera fish poisoning in the Indian Ocean

According to Ciguatera Online, ciguatera fish poisoning (CFP) affects between 25,000 and 50,000 people worldwide annually. Approximately 400 million people are at risk. The online research states that the figures for CFP, the most widespread foodborne illness, are likely to represent only 20% of actual cases due to a lack of information and incorrect or delayed diagnosis. Many people with CFP prefer to treat themselves without consulting a physician, since there is no efficient or specific treatment. As a result, these cases are not taken into account.

Mira Devi Hurbungs is an Australia Awards Alumna who works in the Ministry of Fisheries of the Government of Mauritius as an Assistant Director. She joined the Ministry in 1991 as a scientist and was responsible for the Fish Toxicity Project. In 1995, she was supported to attend a Short Course on Research on CFP at the Centre for Drug Design and Development, presented by staff of Gerhmann Laboratories, which is based on the University of Queensland’s St Lucia Campus in Australia.

According to Mira, CFP is present in many tropical island countries within the circumtropical belt, which has a coral reef ecosystem. She says that this form of poisoning is caused by the ingestion of a marine macro alga by herbivorous fish, which are in turn eaten by carnivorous fish. A person gets affected immediately after consuming the toxic fish. The toxins do not affect the look, smell, texture or taste of the fish. Freezing, salting, filleting, cooking, smoking or any other fish preparation method does not destroy the toxins or diminish their toxicity. Outbreaks can occur seasonally or irregularly, mostly after storms. Any reef fish can spread CFP, but bigger species are the most commonly affected. Ciguatoxins are concentrated in the heads, intestines, liver and roe of the fish.

Symptoms include nausea, abdominal pain, vomiting and diarrhoea. These can appear one to three hours after eating contaminated fish and may last for days or a number of weeks. This is followed by neurological issues showing up anywhere from three hours to four days later. Long-term effects include chronic fatigue, depression, headache, muscle pain, an irregular or slow heartbeat, and low blood pressure. In extreme cases, the symptoms can last for as long as 20 years, often leading to long-term disability.

Mira says that the knowledge and skills she gained on the Short Course she attended have been tremendously beneficial in tackling CFP back home. “After my return from Australia, I used the new mouse bio-assay to test the presence of ciguatoxin in fish tissue.” She was able to convince the Ministry to acquire the necessary equipment for the extraction of fish tissue in order to test the final extract on white mice in the Ministry’s laboratory at the Albion Fisheries Research Centre in Mauritius.

She explains that while the mongoose feeding assay (analytical test) takes three days, observing mice during the mouse bio-assay takes only a day. Results obtained from both methods were used to prove the toxicity of some carangids (jacks and trevallies) and these have been included in the country’s list of 20 toxic fish species that are prohibited for sale.

In addition to the testing of fish samples for the monitoring of toxic fish, the Ministry has a component for the monitoring of harmful marine micro algae that are associated with CFP.  According to Mira, both locals and tourists are great consumers of fish. “Approximately one million tourists visit the country annually. People have a right to be informed and it is the duty of the government to safeguard their health and assure food safety,” she says.

People are now more aware of CFP following the sensitisation campaigns Mira has aided the government in carrying out island-wide. This is done through talks in schools and in residential areas, the distribution of pamphlets and posters, video clips on television and radio programs.

Under Mira’s leadership, the Ministry has also participated in regional projects of the Indian Ocean Commission member countries, including the regional Harmful Marine Microalgae Project under the Intergovernmental Oceanographic Commission in collaboration with the University of Copenhagen (which regrouped Comoros, Kenya,  Madagascar, Mauritius, Reunion Island, Seychelles and Tanzania).