Fish-borne parasitic zoonoses: Status and issues

The egg the exoskeleton growth and moulting the epidermis musculature the nervous system the pseudocoelom the secretory-excretory system the digestive system the reproductive system nematode pathology.

The Structure of Nematodes

Summary: Infection of humans with the nematode worm parasite Anisakis simplex was first described in the 1960s in association with the consumption of raw or undercooked fish During the 1990s it was realized that even the ingestion of dead worms in food fish can cause severe hypersensitivity reactions, that these may be more prevalent than infection itself, and that this outcome could be associated with food preparations previously considered safe Not only may allergic symptoms arise from infection by the parasites (“gastroallergic anisakiasis”), but true anaphylactic reactions can also occur following exposure to allergens from dead worms by food-borne, airborne, or skin contact routes This review discusses A simplex pathogenesis in humans, covering immune hypersensitivity reactions both in the context of a living infection and in terms of exposure to its allergens by other routes Over the last 20 years, several studies have concentrated on A simplex antigen characterization and innate as well as adaptive immune response to this parasite Molecular characterization of Anisakis allergens and isolation of their encoding cDNAs is now an active field of research that should provide improved diagnostic tools in addition to tools with which to enhance our understanding of pathogenesis and controversial aspects of A simplex allergy We also discuss the potential relevance of parasite products such as allergens, proteinases, and proteinase inhibitors and the activation of basophils, eosinophils, and mast cells in the induction of A simplex-related immune hypersensitivity states induced by exposure to the parasite, dead or alive

Anisakis simplex: from Obscure Infectious Worm to Inducer of Immune Hypersensitivity

The application of molecular systematics to the anisakid nematodes of the genera Anisakis, Pseudoterranova and Contracaecum, parasites of aquatic organisms, over the last two decades, has advanced the understanding of their systematics, taxonomy, ecology and phylogeny substantially Here the results of this effort on this group of species from the early genetic works to the current status of their revised taxonomy, ecology and evolutionary aspects are reviewed for each of three parasitic groups It has been shown that many anisakid morphospecies of Anisakis, Contracaecum and Pseudoterranova include a certain number of sibling species Molecular genetic markers provided a rapid, precise means to screen and identify several species that serve as definitive and intermediate and or/paratenic hosts of the so far genetically characterized species Patterns of differential distribution of anisakid nematodes in various definitive and intermediate hosts are presented Differences in the life history of related species can be due both to differential host-parasite co-adaptation and co-evolution, and/or to interspecific competition, that can reduce the range of potential hosts in sympatric conditions Phylogenetic hypotheses attempted for anisakid nematodes and the possible evolutionary scenarios that have been proposed inferred from molecular data, also with respect to the phylogeny of their hosts are presented for the parasite-host associations Anisakis-cetaceans and Contracaecum-pinnipeds, showing that codivergence and host-switching events could have accompanied the evolution of these groups of parasites Finally, examples in which anisakid nematodes recognized genetically at the species level in definitive and intermediate/paratenic hosts from various geographical areas of the Boreal and Austral regions and their infection levels have been used as biological indicators of fish stocks and food-web integrity in areas at high versus low levels of habitat disturbance (pollution, overfishing, by-catch) are presented

Advances and trends in the molecular systematics of anisakid nematodes, with implications for their evolutionary ecology and host-parasite co-evolutionary processes.

Anisakis simplex: dangerous — dead and alive?

Publisher Summary This chapter reviews the literature on Anisakis, including use of the nematode as a biological tag in applied fishery science. The genetic diagnosis of Anisakis is presented as: three lips, each bearing a bilobed anterior projection, which carries the single dentigerous ridge; interlabia absent; excretory gland with duct opening between ventrolateral lips; oesophagus with anterior muscular portion (preventriculus) and posterior ventriculus, the latter being oblong and sometimes sigmoid or as broad as long; no oesophageal appendix or intestinal caecum; vulva in middle or first third of body; spicules of male unequal; preanal papillae numerous; postanal papillae including a group of three or four pairs set close to the tip of the tail on the ventral side. While euphausiids appear to be important crustacean hosts of Anisakis at least in offshore areas, further is required to show other crustaceans to be significant, possibly in inshore waters. Further investigation may show squid to be of greater significance in the transmission of Anisakis to final hosts than the literature indicates, bearing in mind the importance of squid in the diet of many cetacean species. Several aspects of development remain obscure. In view of the taxonomic importance of the “excretory system” in ascaridoid nematodes, its physiological functions are poorly understood; Anisakis may prove to be a useful experimental model for investigation of these functions. With regard to accidental infection of man with Anisakis, further study might be made of a possible allergic predisposition to severe gastrointestinal reaction.

Anisakis and anisakiasis

Larval Anisakis 7.7 to 23.6 mm long from euphausiids, and larvae 18.0 to 21.9 mm long from a teleost fish were morphologically and morphometrically alike and fitted the description by Beverley-Burton, Nyman & Pippy (1977) of A. simplex L3. Three small larvae, 4.2 to 5.9 mm long, from euphasiids resembled L3 in anterior but not in posterior morphology; their tails lacked a mucron but, in two of them, cuticular separation at the posterior extremity revealed clearly the mucron characteristic of L3 within. These small larvae are identified as L2 of A. simplex in the process of moulting to L3. Japanese reports of typical L3 from 6.9 to 32.7 mm long in euphausiids, the occurrence in teleosts of typical L3 from only 8.8 to over 30 mm long, and the present observations strongly suggest that the moult from L2 to L3 occurs in euphausiids and begins when the larvae are about 4-6 mm long. Although it appears, therefore, that only one moult occurs in the egg of A. simplex (i.e. ensheathed L2 hatches), two moults there have been reported for various terrestrial and certain aquatic ascaridoids (i.e. ensheathed L3 hatches). The morphology and homology of the lips and associated sense organs of A simplex L3 are discussed relative to that of a 'typical' adult ascaridoid. A main conclusion is that euphausiids in the North-East Atlantic and northern North Sea, and perhaps universally, are major intermediate hosts of A simplex. The status as hosts of squid and teleosts harbouring L3 is discussed. An extensive literature is reviewed in relation to the present observations.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022149X00009512

Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878) (Nematoda: Ascaridoidea): morphology and morphometry of larvae from euphausiids and fish, and a review of the life-history and ecology.

Over 26000 specimens representing five euphausiid species collected, mostly in 1969, in the North-East Atlantic and northern North Sea were examined for parasites. Hysterothylacium sp. larvae were rare, occurring in only two euphausiid samples from inshore localities; the 9 larvae found (3.8 to 12.3 mm long) are described and illustrated. Infection with larval Anisakis simplex was virtually restricted to Thysanoessa spp. and appeared to be discontinuous. Infection was absent to the west of Scotland, and rare to the north of Scotland and at the Faroes. Larval A. simplex was not uncommon in offshore regions of the northern North Sea at depths between 100 and 200 m; the prevalence rate there for individual euphausiid species in individual samples was mostly 0 to 40% but an exceptionally high rate of 78.0% was recorded. Larvae in euphausiids do not become encapsulated but appear to remain active. Experimental observations on the sedimentation rate of A. simplex eggs and hatched larvae in sea water at 10°C are discussed in relation to embryonation and hatching at different temperatures, and depth of the sea. New host records are claimed for larval A. simplex in Nyctiplutnes couchii, and for larval Hysterothylacium sp. in Thysanoessa inermis. No individual euphausiid harboured more than one parasite, either larval nematode or ellobiopsid (see also SMITH, 1981). Morphological and morphometric observations on larval A. simplex from euphausiids are reported elsewhere (SMITH, 1983).

Larval Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878) and larval Hysterothylacium sp. (Nematoda: Ascaridoidea) in euphausiids (Crustacea: Malacostraca) in the North-East Atlantic and northern North Sea

Third-stage larvae (L3) of Anisakis simplex of a known minimum age of 60 to 61 weeks, the oldest of which may have spent at least three years in herring, were artificially excapsulated in saline and appeared healthy. A small proportion succccded in penetrating the gut wall of rats. The length distribution of L3 of minimum age 18 to 23 weeks did not differ significantly from that of larvae of minimum age 60 to 61 weeks.

Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878): length distribution and viability of L3 of known minimum age from herring Clupea harengus L

Batches of 10 Anisakis larvae from Greenland salmon (Salmo salar) were labelled with radioiodcin and fed to 10 haddock (Melanogrammus aegiefimis). Similar batches of larvae from herring (Clupea harengus) were fed to 8 whiting (Merlangius merlangus). At post-mortem from 15 to 190 hours after infection, 0 to 6 larvae were recovered from whiting (over-all recovery rate 18.8%) and 0 to 4 larvae were recovered from haddock (over-all recovery rate 27%). Larvae penetrated the wall of the stomach or of a pyloric caecum. They were first seen in the body-cavity 24 hours after infection and a delicate capsule was present around some of them by 34 hours. Most larvae were recovered from the body-cavity but, in haddock, two had penetrated the epaxial musculature.

John W. Smith

Papers

Anisakis and anisakiasis

Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878) (Nematoda: Ascaridoidea): morphology and morphometry of larvae from euphausiids and fish, and a review of the life-history and ecology.

Larval Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878) and larval Hysterothylacium sp. (Nematoda: Ascaridoidea) in euphausiids (Crustacea: Malacostraca) in the North-East Atlantic and northern North Sea

Anisakis simplex (Rudolphi, 1809, det. Krabbe, 1878): length distribution and viability of L3 of known minimum age from herring Clupea harengus L

Experimental transfer of Anisakis sp. larvae (Nematoda: Ascaridida) from one fish host to another.