淮河水系毛毕吸虫尾蚴生态的初步研究

目的　了解淮河水系毛毕吸虫尾蚴的生态习性及特征。　方法　 2002年6月至2003年5月,在安徽省淮南市郊淮河水系支流窑河渔场,逐月采集耳萝卜螺压片镜检,用感染毛毕吸虫的阳性螺逸尾蚴,滴瓶遮光法收集尾蚴。用不同时龄尾蚴感染雏鸭,以三角烧瓶顶管法孵化毛蚴检测雏鸭感染率。　结果　螺体内尾蚴检出率呈明显的季节消长,尾蚴检出率7月份为0.81%,6月为0.65%,4～5月和8～10月均为0.07%～0.26%,逐月差异具有极显著性意义(P<0.01)。尾蚴逸出数量呈明显的日周期变化,每天上午8:00～12:00为逸蚴高峰期,温度和光照影响显著。尾蚴具有强烈的趋光性,自然变温 (18～25℃)下最长寿命为52h,半数死亡时间为41h。对雏鸭感染力与尾蚴时龄关系密切,30min～8h时龄感染力最强,40h以后感染力丧失。　结论　初步探明淮河水系毛毕吸虫尾蚴的生态习性及特征。

Preliminary Study on the Ecology of Trichobilharzia Cercariae in the Huaihe River System

OBJECTIVE: To investigate the ecological habit and characteristics of Trichobilharzia cercariae in the Huaihe river system. METHODS: During June of 2002-May of 2003, Radix auricularia snails were collected monthly in Yaohe Fishery of the branch of the Huaihe River. The cercariae, released from the positive snails and collected by Shade Drop Bottle, were examined by direct press. Ducklings were infected by cercariae with different ages and examined for the infection by miracidia hatching method. RESULTS: The results showed a typical seasonal fluctuation in infection rate of the snails, i.e. the cercariae detection rate was 0.81% in July, 0.65% in June, 0.07%-0.26% in April, May, August, September and October respectively, with a significant difference (chi2 = 26.73, P < 0.01). The release of cercariae from the snails showed a diurnal pattern in the natural conditions, with a significant peak between 8:00-12:00. It was proven that the main factors affecting the emerging of cercariae were temperature and light. The cercariae showed positively phototaxis. It was also showed that 50% mortality of the newly released cercariae between 18-25 degrees C occurred at 41 h, and all cercariae died within 52 h. The infectivity of cercariae was age-dependent. Under 18-25 degrees C, the highest infectivity was found at 0.5-8 h after emergence, then declined steadily to negative by 40 h post-emergence. CONCLUSION: The ecological characteristics of Trichobilharzia cercariae have been preliminarily verified in the Huaihe river system.