Tetragomphius sp.寄生膵の病理学的所見(第1報) : アナグマ膵管の特異的病変について

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　近年,宮崎県下で捕獲したアナグマ6例及び大分県下で捕獲した2例のいずれにもTetragomphius sp. の寄生を認めた. このことから東九州地方に生息するアナグマには, Tetragomphius sp. の濃厚感染が起きていることが推測される.　ところでTetragomphius sp. の寄生を受けたアナグマ膵臓(膵管)の病理所見を検討した結果,若干の興味ある知見を得ることができた. すなわち膵管の十二指腸開口部から侵入した本虫は,膵液の分泌流に抗しつつ膵管をさかのぼり,その起始部(腺体の先端部)へ向う性質が極めて強いようである. 起始部に到達してそこに定着した虫体は,その部分に持続的･集中的な刺激を及ぼす結果,該部に著明な増殖性炎を起こす. その形態的表現として,膵管起始部の管壁結合織に限局的な著明増殖が起き,全体として結節状ないし腫瘤状の病変を形成する.腫瘤のとくに大きいのはクルミ大を呈するものもあるが,一般には小豆大･大豆大ないし小指頭大である.腫瘤の内腔に寄生する虫体数は意外と少なく,少数の虫体で特異な病変を生起するところをみると,本虫の刺激作用(器械的･化学的)は相当強力であることが推測される.Six Japanese badgers (Meles meles anakuma) were caught in Miyazaki Prefecture over a period from 1974 to 1975. When the pancreas was examined, it harbored Tetragomphius sp. (TG) in all the badgers, and characteristic changes were observed in part of the area of parasitization (pancreatic duct). After that, two samples were collected from badgers caught in Oita Prefecture. Therefore, a total of eight samples of changes of the pancreatic duct were examined pathologically with the following results. 1) The number of nematodes of TG harbored per capita ranged from 12 to 130, being 47.5 on the average. Accordingly, most of the badgers were involved in a mild infection. Only one was moderate in severity of infection. Nematodes were found mainly in the beginning half of the pancreatic duct (the main duct), and a few of them in the terminal half (side of the opening of the duct into the duodenum). From these findings, it was presumed that TG nematodes might have a remarkable ability to go up the stream of secreted pancreatic juice in the pancreatic duct. 2) In all the eight samples, quite characteristic changes were found in the beginning of the pancreatic duct (tip portion of the pancreas). Pronounced hypertrophy and hyperplasia occurred to restricted areas of the wall of the pancreatic duct. For that cause, nodular and tubercular lesions were formed around the lumen of the duct. The tubercles formed ranged from rice grain to the tip of the little finger in size. In an exceptional sample, a tubercle developed to a marvellously large size, or walnut size. In general, only a few flukes were present in the inner cavity of the nodule. It was assumed that an intense proliferative inflammation might have been induced, because the physical and chemical stimulations of TG nematodes were concentrated at a restricted area. 3) The tuberculous lesion showed the following histological changes. The rather thick wall of the tubercle (surrounding the lumen of the pancreatic duct) consisted roughly of two layers, an inner and an outer. The inner layer was composed of granulation tissue or connective tissue affected with a marked infiltration of lymphocytes and plasma cells, and sometimes with an infiltration of histiocytes and eosinophil leukocytes. It presented slight diffuse hemorrhage in some cases. The innermost portion of the inner layer, which faced the lumen of the tubercle became degenerative and necrotic. The outer layer of the wall of the tubercle was composed of a little stale connective tissue and contained only a few infiltrating cells in general. Sometimes, it contained a considerably large number of eosinophil leukocytes. In some cases, crypts were formed by concaving of the epithelium or tubular (mucous) glands appeared in the rather thick wall of the tubercles. The pancreatic tissue surrounding the tuberculous lesion was very narrow. Interstitial proliferation, however, was unexpectedly mild around this lesion. 4) In the pancreatic duct harboring TG nematodes, the area free from changes of formation of tuberculous lesions was affected with a slight dilatation of the lumen, and very mild hypertrophy of the wall when observed by the naked eye. Histologically, it exhibited a mild catarrh of the mucous membrane and a somewhat conspicuous formation of crypts in the epithelium. In short, it was quite strange to find severe changes restrictedly in such particular portion as the beginning of the pancreatic duct, all the area of parasitization being not affected equally with those changes.

著者

芦沢広三
宮崎大学農学部家畜病理学教室

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