Rev: 01/04/2023
Chromadorea
Chromadoria
Rhabditida
Spirurina
Ascaridoidea
Anisakidae
Anisakis Dujardin, 1845
Type species of the genus: Anisakis dussumierii (Beneden, 1870) Baylis, 1920 (sensu Mozgovoy, 1953).
Synonyms:
Ref: Safonova et al. 2021
Anisakis simplex may reach a length of 2-4 cm.
Nematodes of the genus Anisakis (Nematoda: Anisakidae) are parasites of marine organisms. The life cycle of these nematodes requires marine mammals, mainly cetaceans, as the definitive hosts, and crustaceans, fish, and cephalopods as intermediate or paratenic hosts (Klimpel and Palm, 2011).
Humans are accidental hosts due to ingestion of raw or undercooked fish containing the third infective-stage larvae. Human anisakiasis patients suffer from abdominal pain, nausea, vomiting, and/or diarrhea (Dorny et al., 2009).
The following detailed descriptions and lifecycles of nematodes associased with Anisakiasis are provided courtesy of CDC, the Centers for Disease Control and Prevention
Causal Agents
Anisakiasis is caused by the ingestion of larvae of several species of ascaridoid nematodes (roundworms), which are sometimes called herringworm, codworm, sealworm�, in undercooked marine fish. Known human-infecting anisakid species include members of the Anisakis simplex complex [A. simplex sensu stricto, A. pegreffii, A. berlandi (=A. simplex C)], the Pseudoterranova decipiens complex (P. decipiens sensu stricto, P. azarasi, P. cattani, and others), and the Contracecum osculatum complex. Recent genetic studies have revealed high diversity within these anisakid groups, suggesting additional cryptic species are likely represented in zoonotic infections.
Adult stages of anisakid nematodes reside in the stomach of marine mammals, where they are embedded in the mucosa in clusters. Unembryonated eggs produced by adult females are passed in the feces of marine mammals . The eggs become embryonated in water, undergoing two developmental molts , and hatch from the eggs as free-swimming ensheathed third-stage (L3) larvae . These free-swimming larvae are then ingested by crustaceans . The ingested larvae grow within the crustacean hemocoel, and become infective to fish and cephalopod paratenic hosts. After preying upon infected crustaceans, the digested L3 larvae migrate from the paratenic host intestine into the abdominal cavity, and eventually to the tissues of the mesenteries and skeletal muscle. Through predation, tissue-stage L3 larvae can be transmitted among paratenic hosts . Fish and squid maintain L3 larvae that are infective to humans and marine mammals .
When fish or squid containing third-stage larvae are ingested by definitive host marine mammals, the larvae molt twice and develop into adult worms . After ingestion by humans, the anisakid larvae penetrate the gastric and intestinal mucosa, causing the symptoms of anisakiasis .
Dorny, P., Praet, N., Deckers, N. and Gabriel, S. 2009. Emerging food-borne parasites. Veterinary Parasitology 163:196-206.
Klimpel, S. and Palm, H. W. 2011. Anisakid nematode (Ascaridoidea) life cycles and distribution: Increasing zoonotic potential in the time of climate change? In Mehlhorn, H. (Ed.), Progress in parasitology. Parasitology research monographs, Vol. 2 Springer, Berlin, pp. 201-222.
Safonova, A.E., Voronova, A.N., Vainutis, K.D. 2021. First report on molecular identification of Anisakis simplex in Oncorhynchus nerka from the fish market, with taxonomical issues within Anisakidae. J. Nematology 53 :| DOI: 10.21307/jofnem-2021-023