Effects of anisakid nematodes Anisakis simplex (s.l.), Pseudoterranova decipiens (s.l.) and Contracaecum osculatum (s.l.) on fish and consumer health

Abstract

The anisakid nematodes Anisakis simplex (Rudolphi, 1809), Pseudoterranova decipiens (Krabbe, 1878) and Contracaecum osculatum (Rudolphi, 1802) occur as third-stage larvae in marine fish products and may infect consumers ingesting raw or under-cooked fish products. Clinical symptoms associated with the infection, termed anisakidosis, vary from irritation of the oesophagus and stomach, via nausea, vomiting and diarrhoea to severe epigastric and abdominal pain. Third-stage larvae of A. simplex are found in the body cavity, musculature and various organs, P. decipiens occur mainly in the fish musculature (fillet) and C. osculatum larvae reside predominantly in the liver, body cavity, mesenteries and pyloric caeca. Preventive measures, including mechanical removal of worms, heat treatment or freezing to kill worms, are needed in order to reduce the risk of human infections. The anisakid life cycle involves several hosts. A. simplex nematodes use cetaceans (whales) as final hosts whereas P. decipiens and C. osculatum have their adult stage in pinnipeds (seals). Eggs released by worms in these hosts pass with feces to seawater where free-living third-stage larvae hatch from the eggs. Various invertebrates – including euphausiids, copepods and amphipods – feed on these larvae, become infected and serve as intermediate hosts. A range of fish species may serve as transport hosts following ingestion of infected invertebrates and the final stage develops after two additional moults in the stomach of marine mammals which consumed infected fish. Control measures may be implemented to reduce infections of fish stocks and thereby risk of human infections.