大漢溪流域之扁彎口吸蟲感染鯉科魚類之研究

Abstract

扁彎口吸蟲(Clinostomum complanatum)分布範圍廣，宿主以鯉科魚類居多，可感染超過三十種以上的淡水魚類，被寄生的魚隻生長遲緩、體弱且外觀不佳，失去經濟價值。2011年1月至2011年10月檢查桃園地區石門水庫、大漢溪流域及其集水區的淡水魚類15種共448尾，收集到的扁彎口吸蟲之後尾動幼蟲以解剖顯微鏡進行形態鑑定，更進一步利用分子生物學分類法確認，自行設計一組扁彎口吸蟲18S核醣體DNA的專一性引子，經由聚合酶連鎖反應(PCR)，產生長度為1219鹼基對之片段。 調查結果如下，採樣地點中，唯有大漢溪下游與三民溪發現扁彎口吸蟲的感染，在大漢溪下游：平頜鱲感染盛行率為38.8％；平均感染強度12.3隻吸蟲�魚、臺灣石賓28.6％；平均感染強度為100隻吸蟲�魚。三民溪：臺灣石賓感染盛行率75％；平均感染強度為8隻吸蟲�魚、臺灣白甲魚37.5％；平均感染強度為64.3隻吸蟲�魚。受感染的三種淡水魚類皆屬鯉科魚類，而其餘魚種未發現感染情形。此外，將感染部位分為口腔、鰓蓋、下頜、胸鰭、腹鰭、臀鰭、背部、尾柄與其他等九個區域，結果顯示扁彎口吸蟲偏好寄生於鰓蓋下方、口腔與下頜，超過七成以上的後尾動幼蟲寄生在這三個部位，而背部則未發生寄生情形。本次調查結果已證實大漢溪流域為扁彎口吸蟲之盛行區域，臺灣已成為此吸蟲之疫區。

Clinostomum complanatum has a widespread distribution. The parasites can infect more than 30 species of freshwater fish and hosts are mainly cyprinoid. We examined 448 freshwater fish of 15 species in Shihmen Reservoir, Tahan River and the catchment area of Tahan River from January 2011 to October 2011. Observe morphological characters of metacercariae we collected under stereomicroscopy. Then we use molecular methodologies. Polymerase chain reaction (PCR) assay used C. complanatum 18s ribosomal DNA specific primer set we designed and yielded 1219 bp product. The results obtained are as follow, only Tahan River downstream and Sanmin rivulet found the metacercariae of C. complanatum. In Tahan River downstream: the prevalence and mean intensity of parasites in Zacco platypus were 38.8％ and 12.3. Acrossocheilus paradoxus were 28.6％ and 100. In Sanmin rivulet: the prevalence and mean intensity of parasites in A. paradoxus were 75％ and 8. Onychostoma barbatulum 37.5％ and 64.3. These three infected freshwater fish species were cyprinoid. There were no C. complanatum found in other fish species. The body of fish was divided into nine areas: oral cavity, opercle, under the mouth to opercle, pectoral fin, pelvic fin, dorsal part, anal fin, caudal fin. More than 70％ parasites found in oral cavity, opercle and under the mouth to opercle. There were no metacercarie found in dorsal part. The survey results show that invasion of C. complanatum into Tahan River basin. Taiwan has become the endemic area of C. complanatum.