<綜説>寄生虫性肉芽腫の研究実験的胃アニサキス症を中心として

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Histopathological features of infectious diseases caused by parasitic helminths are often characterized by an apparent granuloma formation with a marked infiltration of eosinophils at the site of infection. We have studied this phenomenon using anisakis larvae and laboratory animals as an experimental model. The clinical and pathological status of this disease was established by several investigators in Japan and many articles of anisakiasis have been reported. The condition known as anisakiasis is produced by the migration of anisakis larvae in the tissues of stomach, intestine and other portions of digestive tract of unnatural hosts. Several species of larvae belonging to anisakidae infected in marine fishes and cuttle-fishes may cause this condition in man. The most important etiologic agent of anisakiasis is the third stage larvae of anisakis sp. type I. These larvae show a strong resistance to various physicochemical treatment in vitro. Laboratory animals and man apparently become infected by ingesting these larvae in raw fish meats. The larvae invade into the gastrointestinal tissues of the host and often penetrate into the abdominal cavity. They remain alive for several days but are incapable to complete their development. The sign and symptoms of anisakiasis vary from an asymptomatic state with only a long lasting abdominal discomfort to one characterized by one or many of such symptoms as anaphylactic abdominal pain, nausea, vomiting and others. The severity of infection or the protean of symptoms probably depends upon the site of larval invasion and sensitivity of the patient. Differentiation from such diseases as acute abdominal condition, acute appendicitis, gastrointestinal ulcer or gastrointestinal cancer is necessary. At present the diagnosis of anisakiasis must be based on clinical symptoms or on finding the larvae in biopsy specimens of tissues. Often the worms in the stomach wall can be determined by means of X-ray or fiberscope. We have studied the histopathological features of experimental gastric anisakiasis in rats and guinea pigs. In primary infection, the histopathological reaction of the stomach wall is mostly mild and only a nonspecific foreign body granuloma with neutrophils, mononuclear cells and foreign body giant cells is noted around the invading larvae. In secondary infection, a severe allergic inflammation with edema, hemorrhage and infiltration of eosinophils occurs at the site of infection and results in the formation of eosinophilic granuloma. We concluded therefore that chronic or mild type anisakiasis in man may be due to a primary infection of anisakis larvae and acute or fluminant form may occur as a result of allergic reactions induced by secondary infection. We have also ascertained that excretory or secretory materials as well as somatic substances of anisakis larvae have a strong chemotactic activity for eosinophils. However, the chemotactic activity is more prominent when these substances are introduced into the previously sensitized animals. These results indicate that the chemotactic factors in the anisakis larvae as well as the various immunological reactions may play an important role in the development of eosinophilic granuloma at the site of larval infection. Several investigators are currently attempting to develop immunological methods that will allow the ready diagnosis of anisakiasis. Intradermal test offers a simple means for diagnosis. Indirect hemagglutination test, polymeric or gel sedimentation reaction, and immunoelectrophoresis with purified antigens are useful and Sarles phenomenon offers another simple method for detecting serum antibodies in the sera of patients. However, even with improved purified antigens, these tests lack specificity, and sometimes nonspecific or cross reactions occur.
近畿大学の論文
1980-09-25

著者

宮里昂
近畿大学医学部寄生虫学教室

<綜説>寄生虫性肉芽腫の研究実験的胃アニサキス症を中心として

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