中文摘要：

湖北钉螺先感染外睾吸虫后再感染日本血吸虫,血吸虫幼虫在其体内被击杀（唐崇惕等,2008;2009）,本文用日本血吸虫毛蚴分别接触已感染外睾吸虫21d的钉螺和阴性钉螺,观察血吸虫幼虫在此2组实验钉螺体内发育情况。从感染外睾吸虫钉螺再感染血吸虫的28个（73.7%）阳性螺,查获4～82d血吸虫幼虫共300条（侵入率26.74%）,全部虫体结构异常停留在早期母胞蚴阶段。从单独感染血吸虫的25粒（69.4%）阳性螺,查获5～61d正常血吸虫母胞蚴67条（侵入率13.96%）和许多不同发育期子胞蚴,感染后75d阳性螺含血吸虫成熟子胞蚴和尾蚴。单独感染血吸虫钉螺的血淋巴细胞增生情况与双重感染外睾吸虫和血吸虫的钉螺存在差异。

英文摘要：

Larvae of Schistosorna japonicurn could be blocked in Oncomelania hupensis with pre-infeetion by larval Exorchis trematodes （Tang et al. , 2008, 2009）. The present manuscript reports the result of comparison between the two different developments of larval S. japonicurn in O. hupensis snails with and without pre-infection by larval Exorchis trematodes. Of 300 （invader rate 26.74 %） abnormal larvae of S. japonicum for 4-82 days old were found from 28 （73.7 % ） O. hupensis snails which were pre-infected with Exorchis eggs, their body structure were unusual and developed astray at early mother sporocyst stage. From 25 （69.4 %） O. hu pensis snails without preinfection by larval Exorchis, 67 （invader rate 13.96 %） normal mother sporocysts of S. japonicum for 5-61 days old in different development stages and many early or middle stage daughter sporocysts were found, in the 75th day after infection many mature daughter sporocysts and cercariae of S. japonicurn were found. Different increase of lymphocyte in body tissues of snails were found from the two experimental O. hupensis snail groups.