Tetragomphius sp.寄生膵の病理学的所見(第2報) : テンにおける小型吸虫との混合寄生による膵管病変について

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The pancreas was examined in 34 Japanese martens (Martes melampus melampus) caught in Miyazaki Prefecture during the 1975 hunting season. As a result, the pancreatic duct harbored nematodes of Tetragomphius sp. (TG) in 12 animals (35.3%). In these animals, small flukes (which seemed to belong to Concinnum ten, but which were not identified) were found in the same pancreatic duct with those nematodes. The pancreas (pancretic duct) suffering from mixed infection with TG nematodes and small flukes presented pathological changes which are mentioned below. 1) The number of TG nematodes harbored ranged from 3 to 34, being 11. 2 on the average. It was only one-fourth of that found in the Japanese badgers mentioned in the previous report. The severity of infection was mild in all the 12 martens. The area of parasitization of TG nematodes was the beginning half of the pancreatic duct (main duct) in the left and right lobes of the pancreas in all the martens, except one in which TG nematodes were found in the terminal half of the duct up to the opening into the duodenum. On the other hand, the number of small flukes harbored was large, exceeding one hundred and reaching several hundreds. These flukes were present all over the pancreatic duct, including the terminal half. 2) Many of the 12 martens, as well as the Japanese badgers mentioned in the previous report, exhibited such characteristic changes as tubercular and nodular lesions in the beginning of the pancreatic duct in the left and right lobes of the pancreas. These lesions were noticed in the left lobe in 7 martens and in the right lobe in 5 martens. Of them, tuberculous lesions were observed in both lobes of the same organ in 3 martens. On the other hand, both pancreatic lobes were free from tuberculous lesions in 3 martens. The tubercles formed were from rice grain to soybean in size and generally smaller than those detected in the Japanese badgers. The inner cavity of the tubercle harbored a very small number of TG nematodes. Each tubercle was occupied exclusively with TG nematodes in 9 cases. Another 3 cases, TG nematodes and small flukes were found in the same tubercle. In those cases, the small flukes might have moved incidentally into the tubercle. It was certain that no small flukes had participated in the formation of the tubercle. 3) In principle, the histological findings of tuberculous lesions in the martens were essentially the same as in the Japanese badgers mentioned in the previous report. It was characteristic of them that karyorrhexis and pyknosis had occurred in cells infiltrating into the inner layer of the wall of the tubercle, and that diffuse hemorrhage was considerably severe in both inner and outer layers of this wall. Moreover, the pancreatic tissue surrounding the tuberculous lesion tended show a little more conspicuous interstitial hyperplasia in the Japanese badgers. 4) The areas of parasitization, exclusive of those where tuberculous lesions had been formed, were classified into three kinds of areas harboring TG nematodes alone, these nematodes and small fiukes together, and these fiukes alone, respectively. In general, no marked changes were revealed by the pancreatic duct in these kinds, except mild dilatation and hypertrophy. The number of small flukes harbored was generally large. Therefore, these flukes exerted a mechanical action to make the inner surface (the epithelial line) of the wall of the pancreatic duct flat. Moreover, they had oral suckers which gave rise to small protuberances on the surface of the mucous membrane by their biting and sucking action. Generally speaking, however, it seemed that small flukes might cause no severe lesions, but only mild changes.　昭和50年度の猟期に宮崎県下で捕獲したテン34頭中12例(35.3%)に Tetragomphius sp. の寄生を認めたが,これは本虫種をテンから検出した最初の事例である. しかもこれら12例のテンは, Tetragomphius sp. の単一種寄生ではなく,いずれも Concinnum ten に近似する小型吸虫が混合寄生していた. これら混合寄生を呈するテン膵臓(膵管)の病理所見を検討した結果, Tetragomphius sp. 単一種寄生のアナグマ膵管に認めた特異腫瘤病巣は,テンにも形成されることが確認せられた.テンの膵臓はアナグマと違って左右両葉が明瞭に分かれており,そのため膵管の起始部も左右2カ所あるが,そのいずれにも腫瘤形成が認められた. ただし腫瘤の大きさはアナグマに比し一般に小さい.供試例は膵管系の全般からみると混合寄生であるが,腫瘤に限っていえば大部分は Tetragomphius sp. のみが寄生し,一部に吸虫の混在を認めたに過ぎない.ただし,これら混在吸虫は腫瘤形成後に偶然的に移動してきたものであり,吸虫自体が腫瘤形成に関与したものでないことは明白である.なお吸虫の寄生域(膵管)は一般に管腔の拡張は認めるが,管壁の肥厚は至って軽い.これを要するに,獣種が異なり,しかも混合寄生の状況下でも, Tetragomphius sp. による腫瘤形成の特性は同じように発揮されることが判明した.

著者

芦沢広三
宮崎大学農学部家畜病理学教室

Tetragomphius sp.寄生膵の病理学的所見(第2報) : テンにおける小型吸虫との混合寄生による膵管病変について

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