Anisakis
Anisakis | |
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Anisakis simplex | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Nematoda |
Class: | Chromadorea |
Order: | Rhabditida |
Family: | Anisakidae |
Genus: | Anisakis Dujardin, 1845 |
Species | |
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Anisakis (
Etymology
The genus Anisakis was defined in 1845
Life cycle
Anisakis species have complex
Reproduction
Sexual reproduction occurs once the larvae have reached a definitive host and completed their final molt, at which point sexual organs are developed.[3] Females are capable of producing 2.6 million eggs, depending on species and size at sexual maturity.[4]
The known
Morphology
Anisakis share the common features of all nematodes: the
As with all parasites with a complex life cycle involving a number of hosts, details of the morphology vary depending on the host and life cycle stage. In the stage which infects fish, Anisakis species are found in a distinctive "watch-spring coil" shape. They are roughly 2 cm long when uncoiled. When in the final host, anisakids are longer, thicker, and more sturdy, to deal with the hazardous environment of a mammalian gut.[citation needed]
Health implications
It has been suggested that this section be Anisakiasis. (Discuss ) (January 2024) |
Anisakids pose a risk to human health through intestinal infection with worms from the eating of underprocessed fish, and through allergic reactions to chemicals left by the worms in fish flesh.[6]
Anisakiasis
Anisakiasis | |
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Infectious disease |
Anisakiasis is a human parasitic infection of the gastrointestinal tract caused by the consumption of raw or undercooked seafood containing larvae of the nematode Anisakis simplex.
Within a few hours of ingestion, the parasitic worm tries to burrow though the intestinal wall, but since it cannot penetrate it, it gets stuck and dies. The presence of the parasite triggers an immune response; immune cells surround the worms, forming a ball-like structure that can block the
The first case of human infection by a member of the family Anisakidae was reported in the Netherlands by Van Thiel, who described the presence of a marine nematode in a patient suffering from acute abdominal pain.
Diagnosis
Diagnosis can be made by gastroscopic examination, during which the 2-cm larvae are visually observed and removed, or by histopathologic examination of tissue removed at biopsy or during surgery.[citation needed]
Important clues for the diagnosis of anisakiasis include a recent history of eating raw or insufficiently cooked fish or squid followed by the sudden start of epigastric or right lower quadrant stomach pain. The removal and examination of the larva by gastroscopy or surgery provides a definitive diagnosis.[16]
Prevention
Raising consumer and producer awareness about the existence of anisakid worms in fish is a critical and effective prevention strategy. Anisakiasis can be easily prevented by adequate cooking at temperatures greater than 60 °C[citation needed] or freezing. The FDA recommends all shellfish and fish intended for raw consumption be blast frozen to −35 °C or below for 15 hours or be regularly frozen to −20 °C or below for seven days.[15] Salting and marinating will not necessarily kill the parasites, as in Italy where two-thirds of cases were attributed to anchovies marinated in lemon or vinegar.[17] Humans are thought to be more at risk of anisakiasis from eating wild fish rather than farmed fish. [citation needed] Many countries require all types of fish with potential risk intended for raw consumption to be previously frozen to kill parasites. The mandate to freeze herring in the Netherlands has virtually eliminated human anisakiasis in the Netherlands.[18]
The best preventive measure for Anisiakis is to avoid eating raw or undercooked fish or squid.[19] Another common prevention method is the thermal treatment of the fish or squid prior to consumption. The fish or squid should be cooked at >60 °C for >1 min or frozen whole at −20 °C for >24 h.[20]
Treatment
For the worm, humans are a dead-end host. Anisakis and Pseudoterranova larvae cannot survive in humans, and eventually die. In some cases, the infection resolves with only symptomatic treatment.
Allergic reactions
Even when the fish is thoroughly cooked, Anisakis larvae pose a health risk to humans. Anisakids (and related species such as the sealworm, Pseudoterranova species, and the codworm Hysterothylacium aduncum) release a number of
Acute allergic manifestations, such as
Occurrence
Larval anisakids are common parasites of marine and anadromous fish (e.g. salmon, sardine), and can also be found in squid and cuttlefish. In contrast, they are absent from fish in waters of low salinity, due to the physiological requirements of krill, which are involved in the completion of the worm's life cycle. Anisakids are also uncommon in areas where cetaceans are rare, such as the southern North Sea.[26] Due to having complex life cycles, species specific relationships and their eggs being released in the feces of their definitive host, the identification of anisakids in local fish populations can be a useful tool in assessing the range or migratory patterns of their definitive host.[27]
Unusual hosts of Anisakis larvae in the Southern Hemisphere, rarely reported, include seabirds, sharks, or sea kraits.[28]
Taxonomy
There are currently 13 species known to exist in this genus, with 12 formally described and one additional species given a temporary name (A. simplex sensu Davey, 1971 is a temporary name). There are three additional species classified as taxon inquirendum (A. dussumierii (Brenden, 1870), A. insignis (Diesing, 1851), and A. salaris (Gmelin, 1790) Yamaguti, 1935). There is one another species classified as nomen dubium (A. diomedeae (Linstow)). An additional 17 species names are now currently considered synonyms for the 13 species believed to exist in this genus.[29]
Similar parasites
- Cod or seal worm Pseudoterranova (Phocanema, Terranova) decipiens
- Contracaecum spp.
- Hysterothylacium (Thynnascaris) spp.
See also
References
- ^ Berger SA, Marr JS (2006). Human Parasitic Diseases Sourcebook. Jones and Bartlett Publishers: Sudbury, Massachusetts
- ^ Dujardin F. (1845). Histoire naturelle des helminthes ou vers intestinaux. xvi, 654+15 pp. (Anisakis: p. 220)
- PMID 33322260.
- S2CID 7128855.
- PMID 16800118.
- PMID 17823758.
- ^ WaiSays: "About Consuming Raw Fish" Retrieved on April 14, 2009
- ^ For Chlonorchiasis: Public Health Agency of Canada > Clonorchis sinensis – Material Safety Data Sheets (MSDS) Retrieved on April 14, 2009
- ^ For Anisakiasis: WrongDiagnosis: "Symptoms of Anisakiasis" Retrieved on April 14, 2009
- ^ For Diphyllobothrium: MedlinePlus > "Diphyllobothriasis" Updated by: Arnold L. Lentnek, MD. Retrieved on April 14, 2009
- ^ For symptoms of diphyllobothrium due to vitamin B12-deficiency University of Maryland Medical Center > "Megaloblastic (Pernicious) Anemia" Archived 2011-11-26 at the Wayback Machine Retrieved on April 14, 2009
- PMID 15702862.
- ^ "CDC - DPDx - Anisakiasis". www.cdc.gov. 2019-05-16. Retrieved 2023-02-17.
- ^ PMID 18400801.
- ^ a b Bad Bug Book: Foodborne Pathogens Microorganisms and Natural Toxins Handbook, 2nd edition Food and Drug Administration.
- PMID 20804423.
- PMID 30058531.
- ISBN 978-0-7216-7634-0.
- ^ "Anisakiasis FAQs". www.cdc.gov. 2020-09-16.
- S2CID 221258565.
- PMID 19336962.
- PMID 18427347.
- PMID 16288416.
- PMID 16675338.
- PMID 29637891.
- .
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- ^ Anisakis Dujardin, 1845