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Chapter 11


There are many parts of the world, particularly Japan and Northern Europe, where raw fish is a popular delicacy. When the fish harbor parasites it is not surprising that the human alimentary tract becomes infected. In Japan alone there have been more than 10,000 such cases reported to date, while hundreds of infections have been recorded elsewhere since Van Thiel, Kuipers et al first reported 11 cases in humans from Holland in 1960. Many individuals are unaware of their infection, but in others there are clinical symptoms and even radiological findings which will almost always be misdiagnosed and unrecognized as to their true etiology, especially in non-endemic areas, often resulting in unnecessary surgery. Anisakiasis is one of those conditions which is likely to give the parasitologist much intellectual pleasure but cause the patient's physician, radiologist and surgeon either dismay, chagrin or interest, depending on their respective philosophies! What the infection does to their patients is equally variable!

Synonyms Anisakiasis caused by Anisakis simplex: Herringworm disease. Whaleworm disease. Anisakiasis caused by Pseudoterranova decipiens: Codworm disease. Sealworm disease. Sp: Anisaquiasis. Fr: Hétérochilidiose. Ger: Heringswurm-Krankheit

Definition Anisakiasis is an infection acquired by eating raw, salted, pickled or poorly cooked fish containing the larval stage of the roundworm Anisakis simplex from the family Anisakidae of the order Ascaridida. Other larval nematodes of this family occasionally causing human infection are Pseudoterranova decipiens and Contracaecum osculatum.

Geographic Distribution

Human infection has been recorded most often from Japan and the Netherlands, but the disease has also been reported from Korea, Thailand, New Zealand, Chile, Germany, Switzerland, Spain, France, Belgium, the United Kingdom and North America. The estimated number of infections in Japan is 1,000 per year. In North America there have been at least 50 confirmed cases, chiefly along the West Coast and in Hawaii. Doubtless, many other infections have occurred worldwide and have gone unrecognized. The disease has a seasonal incidence which usually coincides with the major fishing months.

There is a known geographic variation in the site of the lesion in anisakiasis. Initial reports of patients from Holland who had eaten lightly salted infected herring showed ulcers occurred mainly in the ileum. In one series of 92 Japanese patients the stomach was by far the principal site of infection, with the ileum involved in only 30%. This predilection for intestinal anisakiasis in European countries and for gastric infection in Japan and other Asian countries has held true in almost all subsequent reports to date.

Other parasitic species found in raw fish may occasionally cause human infection somewhat akin to anisakiasis. Thus, in Thailand, where raw fish is popular, gnathostomiasis is a more common infection. Petter reported an eosinophilic granuloma in a man seen in Brittany, France, where a sardine nematode of Thynnascaris species was the responsible agent.

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Copyright: Palmer and Reeder

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