宮崎県産イタチの肺吸虫感染について

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　昭和51～53年度猟期に宮崎県下各地区で捕獲したイタチ36頭を剖検し, 肺の肺吸虫性病変を検索した.　一般に肺の肺吸虫性病変の検索に当っては, 虫嚢の存否(肺吸虫成虫の寄生の有無)がまず第一の目標になるが, 今回は虫嚢以外に, 幼若虫の肺組織内穿入病変及び肺胸膜の虫卵性病変をも検索の対象とした. その結果, 虫嚢形成を認めたのは3頭(8.3%)に過ぎなかったが, 他の2種病変を加えると肺吸虫陽性は10頭(27.8%)に達した. もっとも, 後二者の病巣は微小かつ軽微なものが多く, 肉眼所見だけで確診を下すのは容易でない. しかし注意深く観察すると, 多少とも疑わしい所見を呈するので,そのような個所をもれなく組織学的に観察してみた. すなわち慎重な肉眼観察と, 手間をいとわぬ組織検索を併せ行うことにより, 肺吸虫症の陽性率はかなり高くなることが判明した.　従来,宮崎県産イタチの肺吸虫自然感染例の報告はなかったが,今回の検索によりその実態の一部が解明された.Autopsy was performed on 36 weasels caught in various areas In Miyazaki Prefecture in the hunting seasons in 1976, 1977, and 1978. These weasels consisted of 25 belonging to Musteta sibirica itatsi and 11 belonging to M. sibirica coreana. They were examined for pulmonary lesions caused by Paragonimus. In general, the first step of examination for such lesions is to look for the presence of wormcysts; that is, the evidence of infection with mature Paragonimus flukes. In the present investigation, however, observation was made to detect lesions of the pulmonary tissue caused by penetrating immature flukes and changes of the pulmonary pleura induced by Paragonimus eggs in addition to cyst formation. As a result, cyst formation was found in only three cases (8.3%). Cyst formation, lesions of the pulmonary tissue caused by penetrating immature flukes, and egg-induced pleural and subpleural lesions were noticed in ten cases (27.8%). In these cases the animals were actually suffering from Paragonimus infection at that time or had be invaded by this parasite ever before. But the lesions of the pulmonary tissue caused by penetrating flukes, and egg-induced pleural lesions were so minute and mostly so mild that, it was difficult to make a decisive diagnosis of Paragonimus infection macroscopically. Careful observation, however, could detect some or other suspected changes. And foci could be recognized exactly when examind histologically. In conclusion, it was clarified that lesions caused by Pragonimus could be detected at a considerably high rate when careful macroscopical observation and labor-consuming histological examination were carried out simultaneously. By the way, of the three cases of cyst formation, case I had one cyst containing 2 Paragonimus worms and located in the posterior lobe of the left lung. These worms were identified as P. miyazkii. Case 2 had two cysts formed in the anterior and posterior lobes of the right lung, respectively. The walls of these cysts and worms contained in them were calcified so remarkably that it was impossible to identify these worms. Case 3 had 17 cysts which consisted of seven formed in the anterior and posterior lobes of the right lung, respectively, and two and six formed in the anterior and posterior lobes of the left lung, respectively. The surface of the worm body was calcified. Judging from the morphology of the egg, the worms detected were identified as P. ohirai. It is for the first time that the spontaneous infection of weasels produced in Miyazaki Prefecture with Paragonimus worms was reported.

著者

芦沢広三
宮崎大学農学部家畜病理学教室

宮崎県産イタチの肺吸虫感染について

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