钉螺感染目平外睾吸虫的分泌物及其对杀灭不同时间再感染日本血吸虫幼虫的进一步观察

目的 湖北钉螺(Oncomelania hupensis)先感染目平外睾吸虫(Exorchis mupingensis)虫卵后,再间隔不同时间感染日本血吸虫(Schistosoma japonicum)毛蚴,观察螺体分泌物的强度对血吸虫幼虫损害和被杀灭情况的关系。方法 钉螺感染目平外睾吸虫后分别于21 d、37 d、55 d、70 d和85 d再感染血吸虫毛蚴。钉螺经双重感染后4-82 d, 作钉螺整体连续埋蜡切片、染色制片和全片观察,并记录血吸虫幼虫残体数。结果与结论 单独感染外睾吸虫的钉螺,和两吸虫感染间隔时间为21-85 d的钉螺,螺体都产生大量血淋巴细胞和分泌物,它们会围攻再侵入的日本血吸虫早期幼虫并侵入其体内,血吸虫幼虫结构发生异常、停止发育直至死亡。两种吸虫双重感染的间隔时间愈长,螺体血淋巴细胞数随时间增加而逐渐减少;而螺体分泌物不断增多,并见于血吸虫幼虫残骸内,螺体攻击血吸虫幼虫的效力愈强。这现象在单独感染日本血吸虫的钉螺体内未见到。

Observation on the relationship between intension of snails secretion and the condition of wrecked schistosoma larvae in Oncomelania hupensis dually infected with Exorchis mupingensis and Schistosoma japonicum for different intervals

The Oncomelania hupensis snails were dually infected with Exorchis mupingensis and Schistosoma japonicum at different intervals for 21 d,37 d,55 d,70 d and 85 d. The results indicated that the development of all S. japonicum larvae were blocked in the snails of co-infection, and the complexity and number of secretions in and around all the wrecked S. japonicum larvae is proportional to the intervals of co-infection. In addition, we also described and compared the detailed change of snails’ secretions in different conditions of infection, and determined that the snail’s secretions may involve in the destruction and damage of S. japonicum larvae. The attack degrees on larval S. japonicum in O. hupensis snails dually infected by E. mupingensis and S. japonicum with longer intervals were stronger than that of shorter intervals, and snail haemo-lymphocytes numbers were more few in that of shorter intervals. But the secretions remarkably increased in more longer interval model experimental snail tissue. This finding may provide an alternative strategy for reducing and controlling the transmission of S. japonicum, and are very helpful for better understanding the host-parasite relationship.