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目的探索感染小鼠的血吸虫尾蚴时龄增加至何水平时,小鼠不随粪便排出虫卵。方法取新鲜逸出的尾蚴20条置于盛有去氯水的短试管中,20~25℃恒温放置2~72 h后,采用尾部浸泡法感染小鼠,感染小鼠饲养42 d,连续3天收集粪便,镜检判定粪便中血吸虫虫卵排出情况,浓集法计数每克小鼠粪便虫卵数量(EPG)。最后解剖实验小鼠,灌注法收集成虫,计算小鼠感染率及体内虫负荷水平。结果当感染尾蚴的时龄增加至24 h,12只小鼠中仍有1只在感染后42~44 d随粪便排出虫卵,而当感染尾蚴的时龄增加至48 h,12只小鼠中未出现成功感染的小鼠。随着感染尾蚴时龄的增加,粪便中排出虫卵的小鼠数量减少。结论血吸虫尾蚴在水体中虽不摄取营养,但尾蚴体内储存的能量足以维持其自钉螺逸出后24h内成功感染小鼠并使其随粪便排出虫卵,从而使血吸虫生活史得以延续。
Objective To explore when mice infected with Schistosoma japonicum cercariae increased to what level, the mice do not excrete eggs with the feces. Methods Twenty freshly-released cercariae were placed in a short test tube containing dechlorinated water. After being kept at 20-25 ℃ for 2 ~ 72 h, the mice were infected by tail immersion method. The infected mice were fed for 42 d for 3 consecutive days Days to collect feces, microscopic examination to determine the excretion of schistosomiasis eggs in excrement, concentration method count per gram of mouse fecal egg number (EPG). At last, the mice were dissected and the adults were collected by perfusion method to calculate the infection rate of mice and the level of insect burden in mice. Results When the age of cercariae was increased to 24 h, one out of 12 mice still excreted eggs with feces at 42-44 d after infection, but increased to 48 h when infected with cercariae. Twelve mice No successful infection in mice. As the age of cercariae is increased, the number of mice excreted in the stool decreases. CONCLUSIONS Although schistosome cercariae do not ingest nutrients in water, the energy stored in cercariae is sufficient to maintain the infected mice within 24h after they have escaped from the snails and excrete the eggs with the excrement so that the life history of the schistosomes can be continued.