Clinical features diagnosis and treatment

In warm-blooded hosts, anisakid larvae will attempt to develop to maturity; in their normal hosts they will succeed, but in abnormal ones - man being one - they may fail. In man, clinical symptoms of anisakidosis include nausea, vomiting, abdominal and gastric pains, diarrhoea, and sometimes urticaria. Some ingested larvae pass through the digestive tract and are voided via anus, but the majority attempt to attach to, and bore into, the mucosa of the digestive tract, challenging the host's defences, resulting in oedema, eosinophilia, and often eliciting acute gastric pains. In Japan, suspected cases of gastric anisakidosis are now routinely diagnosed by gastric endoscopy, and forceps attached to the instrument can easily remove any visible larvae. Intestinal anisakidosis is difficult to diagnose by endoscopy; in such cases X-rays, ultrasound, immunodiagnosis, and serodiagnosis (see Ishikura and Kikuchi 1990) are options. Anisakis simplex larvae may even migrate into other organs, such as liver and pancreas, deep into the wall of the digestive tract and even into the abdominal cavity. Larva embedded in gut wall elicit oedema with eosinophilia, immune reactions, inflammatory lesions; ulcers and vanishing tumours; in histological sections degenerate larvae surrounded by necrotic tissue may be seen (see Ishikura and Kikuchi 1990). Anisakidosis is not lethal, but if not diagnosed and treated it may linger on with diffuse symptoms.

According to Ishikura et al. (1992) 14000 reported cases of anisakidosis were known, of these about 90% were gastric, and 10% were intestinal. In countries other than Japan, these values may be reversed; one reason being that the Japanese doctors are very adept at diagnosing the gastric variety. Reviewing the known cases of anisakidosis, Ishikura et al. (1992) stated that of the more than 12000 cases in Japan, P. decipiens was involved in only 335. Outside Japan, anisakidosis was reported from 19 countries; a table gives a total of 392 A. simplex cases known for the Netherlands. New cases are still reported from various countries, in France 55 are known (Bouree et al. 1995). Ishikura et al. (1998) revised the accumulated anisakidosis cases worldwide by end of 1997 to 35000, about 32300 of them from Japan. Searching Anisakis on the Internet yields many more recent reports.

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