血吸虫对吡喹酮抗药性的研究ⅩⅦ 日本血吸虫吡喹酮抗性株在小鼠体内的生物学特性

Studies on resistance of Schistosoma to praziquantel XVII Biological characteristics of praziquantel-resistant isolates of Schistosoma japonicum in mice

目的实验观察日本血吸虫吡喹酮抗性株在终宿主小鼠体内的生物学特性,探索日本血吸虫吡喹酮抗性株对终宿主的致病力及传播强度。方法分别采用日本血吸虫江苏吡喹酮敏感株和抗性株、湖南吡喹酮敏感株和抗性株尾蚴定量感染小鼠,建立小鼠-钉螺-小鼠生活史循环,观察比较各虫株的虫卵开放前期、产卵量及虫卵分布、对终宿主的易感性、虫体生长发育等生物学特性。结果日本血吸虫江苏吡喹酮敏感株和抗性株虫卵开放前期分别为36.1 d和36.8d(t=0.907,P=0.372),粪便中虫卵数分别为14.6只/100 mg和21.2只/100 mg(t=2.946,P=0.007),回收成虫数分别为20.5条/鼠和25.1条/鼠(t=2.128,P=0.042),组织中虫卵数分别为31 303只/对成虫和38 594只/对成虫(t=2.185,P=0.040)、肝脏虫卵数分别为14 810只/对成虫和19 715只/对成虫(t=2.934,P=0.007),肠组织中虫卵数分别为16 493只/对成虫和18 879只/对成虫(t=1.044,P=0.309);江苏敏感株和抗性株雌雄合抱虫体长度(t=0.328,P=0.744)、雌虫体长(t=0.386,P=0.701)及雄虫体长(t=0.332,P=0.741)差异均无统计学意义。日本血吸虫湖南吡喹酮敏感株和抗性株虫卵开放前期分别为35.5 d和35.6 d(t=0.169,P=0.867),粪便中虫卵数分别为13.3只/100 mg和18.9只/100 mg(t=3.622,P=0.001),回收成虫数分别为17.6条/鼠和25.1条/鼠(t=3.153,P=0.004),组织中虫卵数分别为30 932只/对成虫和53 903只/对成虫(t=3.865,P=0.001),肝脏虫卵数分别为12 307只/对成虫和26 363只/对成虫(t=4.388,P<0.01),肠组织中虫卵数分别为18 625个/对成虫和27 541个/对成虫(t=2.679,P=0.012);湖南敏感株和抗性株雌雄合抱虫体长度(t=0.853,P=0.397)、雌虫体长(t=0.573,P=0.569)及雄虫体长(t=0.742,P=0.461)差异均无统计学意义。结论日本血吸虫吡喹酮抗性株产卵量和肝组织虫卵沉积量均明显高于敏感株,提示其对终宿主的致病性更强;抗性株感染鼠粪便中排出虫卵数明显多于敏感株,提示抗性株的传播能量高于敏感株。

Objective To investigate the biological characteristics of the praziquantel-resistant isolate of Schistosoma japoni-cum in mice,so as to explore the pathogenicity to definitive hosts and transmission intensity of the praziquantel-resistant isolate of S. japonicum. Methods Mice were infected with the cercariae released from two praziquantel-resistant isolates and two pra-ziquantel-susceptible isolates of S. japonicum. The mouse-Oncomelania hupensis snail-mouse cycle was established and main- tained in the laboratory. The prepatent period of parasite eggs,egg production,egg distribution in mice,parasite susceptibility to mice and egg size were investigated in each parasite isolate. Results The prepatent period of parasite eggs,egg counts in mouse feces,adult worms recovered from each mouse,egg counts in mouse tissues,egg counts in the mouse liver,and egg counts in intestine tissues were 36.1 d and 36.8 d （ t=0.907, P=0.372 ） , 14.6 / 100 mg and 21.2 / 100 mg （t=2.946, P=0.007）,20.5 and 25.1 worms per mouse（t=2.128, P=0.042）,31303 and 38594 per paired adult worm（t=2.185, P=0.04）,14810 and 19715 per paired adult worm（t=2.934, P=0.007）,and 16493 and 18879 per paired adult worm（t=1.044, P=0.309）in the mice infected with Jiangsu praziquantel-susceptible and-resistant isolates of S. japonicum, respectively,and there were no significant differences between Jiangsu praziquantel-susceptible and-resistant isolates of S. ja-ponicum in the length of paired adult worms（t=0.328, P=0.744）,female adult worms（t=0.386, P=0.701）or male adult worms（t=0.332, P=0.741）. The prepatent period of parasite eggs,egg counts in mouse feces,adult worms recovered from each mouse,egg counts in mouse tissues,egg counts in the mouse liver,and egg counts in intestine tissues were 35.5 d and 35.6 d（t=0.169, P=0.867）,13.3/100 mg and 18.9/100 mg（t=3.622, P=0.001）,17.6 and 25.1 worms per mouse（t=3.153, P=0.004）,30932 and 53903 per paired adult worm（t=3.865, P=0.001）,12307 and 26363 per paired adult worm （t=4.388, P〈0.01）,and 18625 and 27541 per paired adult worm（t=2.679, P=0.012）in the mice infected with Hunan praziquantel-susceptible and-resistant isolates of S. japonicum,respectively,and there were no significant differences between Hunan praziquantel - susceptible and - resistant isolates of S. japonicum in the length of paired adult worms （t=0.853, P=0.397）,female adult worms（t=0.573, P=0.569）or male adult worms（t=0.742, P=0.461）. Conclusions The praziquantel-resistant isolate of S. japonicum has a higher parasite egg production and more eggs deposited in the mouse liver than drug-susceptible isolate,suggesting that the praziquantel-resistant isolate of S. japonicum exhibits a greater pathogenicity to definitive hosts. In addition,more parasite eggs are detected in the feces of mice infected with the praziquantel-resistant isolate of S. japonicum relative to the drug-susceptible isolate,indicating that the praziquantel-resistant isolate of S. japonicum exhibits a greater transmissibility than the drug-susceptible isolate.