【摘要】 在平原水网地区的河道,于春秋季,以少量毛蚴（200条及以下）多次投放（连续6d共投放12次）于紧靠装有阴性钉螺尼龙纱袋的水体中。进行现场感染实验。结果每次投放毛蚴数少至25条,每点钉螺数少至1只时,重复观察200个实验点,未发现钉螺被感染。当投放毛蚴数(?)25条,且每点钉螺数(?)5只时,很低度感染（0.24％～1.18％）可能发生。更多还原

【Abstract】 The field study was carried out in the rivers of plain region during spring and autumn. Schistosome miracidia in small numbers (≤200) were disposed repeatedly (12 times in 6 days) to various spots where nylon bags containing different numbers of schistosome-free Oncornelania snails were emerged. Results showed that no snail was infected when a single snail was exposed to≤25 miracidia in 200 spots with repeated trials, and only very few (0.24% - 1.18%) were infected in other expe-riments when≥5 snails were exposed to≥25 miracidia.更多还原