Vomiting, diarrhoea and cold pain after eating fish
As a rule, the first symptoms experienced are nausea, vomiting and diarrhoea. Most people suffering from ciguatoxin poisoning later also suffer from extremely unpleasant sensations such as burning, tingling, and pain on contact with cold. These symptoms can continue for weeks or even months. If such symptoms occur after eating fish, it is very likely that the person concerned is suffering from Ciguatera, i.e. ciguatoxin poisoning. The official control laboratories, the Poison Information Centre of North Germany and other public health and veterinary authorities reported 14 cases of such poisoning following consumption of red snapper fillets to the National Reference Laboratory for Marine Biotoxins and the Centre for Documentation and Assessment of Poisonings at the Federal Institute for Risk Assessment (BfR) at the end of 2012. The trigger are metabolites produced from algae belonging to the group of so-called species of dinoflagellates which are found on coral reefs of subtropical and tropical marine areas of the Caribbean, the Indian ocean and the Pacific. These algae serve as food for plant-eating fish. If these small fish are eaten in turn by predatory fish, the toxins can accumulate and thus get into the human food chain. "Ciguatoxin poisoning is one of the most common types of fish poisoning worldwide", says Professor Dr. Dr. Andreas Hensel, President of the BfR. "However, this type of poisoning was confined to certain regions of the world until recently. As a result of the worldwide trade with tropical and subtropical fish, an increase in incidence of such poisoning is to be expected." The Federal Institute for Risk Assessment has sent leftovers of fish dishes eaten by affected persons as well as samples of the fish batches to the European Reference Laboratory for Marine Biotoxins in Vigo (Spain). Using the analysis method established there in 2012 it was confirmed that the fish samples contained ciguatoxins.
According to estimates, between 50 and 500 thousand cases of ciguatoxin poisoning occur every year. In Germany, such fish poisoning used to be known as very rare travel diseases occurring among tourists who had spent their holiday in tropical or subtropical countries where they had eaten fish dishes. The current outbreak is the first one which was caused by the consumption of fish purchased in Germany. According to a study, the outbreak was caused by red snapper fillets which a German importer had obtained from an Indian distributor. The affected shipment was recalled immediately after poisoning became known.
Ciguatoxins require exceptionally sensitive analysis methods, since ciguatoxins cause symptoms in extremely low concentrations. Different chemical structures of Ciguatoxins are known which, in addition, can vary in dependence of the territorial fishing areas. Until 2012, there was no analysis method allowing fish to be tested for ciguatoxins in the relevant concentration range.
The European Reference Laboratory for Marine Biotoxins (EURL) in Vigo (Spain) established an analysis method for the detection of ciguatoxins in 2012 and found ciguatoxins in most of the fish samples collected in Germany in connection with the outbreak. However, this method is not as yet available for routine testing.
There is no way for consumers to tell whether fish contains ciguatoxins or not. Contamination with ciguatoxins cannot be reduced by frying or cooking. This means that the risk can only be minimised if fish is sold in the market which comes from fishing areas in subtropical and / or tropical waters that are far away from coral reefs or if consumers refrain from eating predatory fish from these waters altogether. In addition, the origin of the fish products must be comprehensively documented and completely traceable.
Following poisoning with ciguatoxins, early symptoms such as nausea, abdominal pains, stomach-ache, vomiting and diarrhoea occur which are also characteristic of other types of food poisoning. These symptoms are soon accompanied or replaced by the typical impaired neurological sensation on the skin such as a feeling of numbness in the hands and feet, muscle pain, physical weakness and notably abnormal heat and cold sensations. The latter symptoms can, in some cases, persist for weeks or months. There is currently no specific therapy.
About the BfR
The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.