ドロレス顎口虫の寄生によるイノシシ胃壁の病変について-1-肉眼的所見

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　宮崎県下に生息するイノシシには極めて高率にドロレス顎口虫が寄生するが,寄生胃15例の肉眼的病変を検索して以下の知見を得た.　1. 顎口虫の主たる寄生部位は胃底である.その粘膜面に寄生孔を形成し,虫体の前半(頭側)を孔内にそう入,後半(尾側)を胃腔へ突出させて寄生する.寄生孔の数は最多例で30コ以上,最少例で3コ,平均11.5コ. 寄生孔に寄生する虫体(すなわち最終寄生態勢の虫体)の数は最多例で52匹,最少例で2匹,平均17匹(寄生孔から脱落して胃内容物に混在する虫体を含む).なお虫体の大きさ(体長)は,大は30mm,小は7mm とすこぶる大小不揃を呈していた.　2. 寄生孔を中心として胃壁(主として粘膜下織)は増厚を呈するが,その程度はとくに著しいものではなく,最厚18mm (うち粘膜下織の厚さは12～13mm)を越えない.また増厚域の範囲も比較的狭い.増厚部の粘膜下織は硬い結合織より成るが,水腫性疎開を呈するものもあった.なお増厚域に虫体(幼若虫･成虫)の穿入･埋在を認めたものがある.　3. 増厚域の粘膜下織(一部は筋層･漿膜)には,各種発育段階の虫体が穿行･遊走したあとの病変(虫体穿行跡の病巣)が極めて高率に検出せられた. この種の病巣を微小巣と虫道巣に区分するが,前者は肉眼で辛うじて認められる程度のごく小さく(針尖大)かつ限界明瞭な結節性の病巣,後者はいくぶん大きく粟粒大･米粒大で暗褐紅色を呈し,境界のやや不明瞭な不斉形の病巣である.なお両者の中間移行型も認められた. このうち微小巣は,寄生孔からかなり離れて胃壁増厚を呈しない部位からも検出せられた.　4. 噴門部に虫体の侵入･寄生を認めたものが供試胃の約半数あった.また噴門部の胃壁(主として粘膜下織)に微小巣･虫道巣を所見したものもはば同数. ただし病変の程度は胃底に比べるとはるかに軽少である.幽門部においても, 6例に虫体の穿入･寄生と胃壁(主として筋層)に虫体穿行跡病巣を所見した.Wild boars (Sus scrofa leucomystax) inhabiting Miyazaki Prefecture are infected with Gnathostoma doloresi at a very high frequency. Observation was made on macroscopical changes in the stomachs infected with this parasite of 15 wild boars collected in the shooting seasons in 1975-1977. The findings obtained are as follows. 1. The fundus was a main locality of infection with G. doloresi. The parasite formed a parasitic hole on its mucosal surface. The cranial half of its body was inserted into the hole, and the caudal half projected into the gastric cavity. The number of parasitic holes per stomach ranged from 3 to more than 30, averaging 11. 5. The number of parasitic worms per stomach ranged from 2 to 52, averaging 17. The body length of the parasite was quite variable, ranging from 7 to 30mm. 2. The gastric wall (mainly the tunica submucosa) became thick around the parasitic hole. Its thickness, however, did not exceed 18mm (the tunica submucosa was 12-13mm in thickness). And the increase in thickness was not seen in so wide an extent. The tunica submucosa was generally composed of hard connective tissue, and some part of it presented edematous dissociation. Immature and young adult worms were found buried in the thickened tunica submucosa in some cases. 3. Lesions caused by the penetration and migration of immature and young adult worms were found at a high frequency in the gastric wall around parasitic holes (mostly in the tunica submucosa and partly in the tunica muscularis and serosa). They were divided into two types of foci. One type was called a micro-focus, which was a well-defined nodular focus so small that it was hardly observed macroscopically. The other type was called a migratory-route focus, which was a dark brownish red irregular shaped focus 3-5mm in diameter, and its demarcation was a little indistinct. Micro-foci were also noticed in some portions of the gastric wall which were considerably far from any parasitic hole and showed no thickening. 4. In 7 cases worms entered the cardiac region by perforation and stayed there, inducing migratory-route and micro-foci in the gastric wall. In 6 cases worms were harbored in the pyloric region, and both types of foci found in its gastric wall.
宮崎大学農学部の論文

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芦沢広三
宮崎大学農学部家畜病理学教室

ドロレス顎口虫の寄生によるイノシシ胃壁の病変について-1-肉眼的所見

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