Abstract:

  Objective   To compare the susceptibility between the male and female cercariae of praziquantel-susceptible and praziquantel-resistant isolates of Schistosoma mansoni in order to explore the resistance mechanism of Schistosoma to praziquantel. Methods   Two isolates of Schistosoma manaso-ni including a praziquantel-susceptible and a praziquantel-resistant isolate were established in the lab.The miracidia were produced by hatching eggs collected  from faeces of the infected mice. The single- sex cercaria lines were made by infecting a single Biomphalaria glabrata snail with a single miracidi-urn The sex of single-sex cercariae lines was identified by a direct Wl-specific PCR technique.  The single-sex cercariae of 2 isolates were exposed in the solutions of 10-4 ,10-5 ,6 X10-7mol/L and 4X 10-7 mol/L praziquantel respectively.  The tail shedding of cercanae was observed un-
 der a dissecting microscope for 0, 20, 40, 60, 80 and 100 minutes after adding praziquantel. The numbers of cercariae which had shed tails were countecL The differences of the tail shedding rates between the male and female cercariae of praziquantel-susceptible and praziquantel-resistant isolates were comparecL  Results   When the cercanae were exposed to the solutions of 10-4 ,10-5 ,  6 X 10-7 mol/L and 4 X 10-7 mol/L praziquantel for 100 min,  in the praziquantel-susceptible isolate of S. mamasoni,  the tail shedding rates of male cercariae were 66. 7%,  75. 8% ,  43. 5%  and 21. i% ,  re-
spectively, while the tail shedding rates of female cercariae were 29.3%,  27.9%,  12. 1% and 7. 6%,  the tail shedding rates of male cercanae were Hgher than those of the female (all P <0. 05) ; in the praziquantel-resistant isolate,  the tail shedding rates of male cercariae were 43. 3% ,  39. 4%,
25. 4% and 6. 9%,  respectively,  while the tail shedding rates of female cercariae were 47. o%, 38. 9%, 26. 3% and 6. 3%, respectively, and there were no differences of the tail shedding rates between the male and the female (all P>O. 05).  When the cercariae were exposed to the solutions of
10-4 ,10-S ,  6 X 10-7 mol/L and 4 X 10-'r moI/L praziquantel for 80 min,  the tail shedding rates of male cercariae of the praziquantel-susceptible isolate were 54. 4% ,  68. 6%,  42. 1%  and 16. 1% ,  respectively,  while those of male cercariae of the praziquantel-resistant isolate were 30. 2% ,  34. 4%,
20. 1% and 2. 8%, raspectively, and the tail shedding rates in the praziquantel-susceptible isolate were higher than those in the praziquantel-resistant isolate (all P<O. 05).  Conclusions   There is asignificant difference of the susceptibility between the male and female cercariae of S. mansoni, andthe male cercariae of S. mansoni are more susceptible to praziquantel than the female cercariae.  It is considered that the resistance of S. mamasoni to praziquantel is induced by the decrease of the susceptibility of male worms to praziquantel

摘要：

 目的比较曼氏血吸虫吡喹酮敏感株、抗性株雌性与雄性尾蚴对吡喹酮敏感性的差异，为探索血吸虫对吡喹酮抗性产生机制提供线索。方法分别用曼氏血吸虫吡喹酮敏感株、抗性株感染鼠粪便中的虫卵孵化毛蚴，以单只毛蚴感染单只光滑双脐螺，建立单性别血吸虫尾蚴系；以WI特异性序列为引物，采用直接PCR法鉴别出单性别系尾蚴的性别，分别将敏感株与抗性株的雌、雄尾蚴暴露于不同浓度的毗喹酮溶液中，经一定时间后观察并计算尾蚴的断尾率。结果曼氏血吸虫尾蚴
暴露于10-4、10_5、6×10-7 mol/L和4×10-7 mol/L毗喹酮溶液中100 min，吡喹酮敏感株雄性尾蚴的断尾率分别为66. 7%、75. 8%、43. 5%和21. 7%．雌性的断尾率分别为29. 3%、27. 9%、12. i和7. 6%，雄性尾蚴的断尾率显著高于雌性尾蚴(P均<0. 05)；而抗性株雄性尾蚴的断尾率分别为43. 3%、39. 4%、25. 4%和6.9%，雌性尾蚴的断尾率分别为47. 0%、38. 9%、26. 3%和6.3%，两者间差异无统计学意义(P均>0.05)。曼氏血吸虫尾蚴分别暴露于10_4、10_5、6×10-7 mol/L和4×10-7 mol/L吡喹酮溶液中80 min，敏感株雄性尾蚴的断尾率分别为54. 4%、68. 6%、42. 1%和16. 1%，抗性株雄性尾蚴的断尾率分别为30. 2%、34. 4%、20. 1%和2.8%，敏感株显著高于抗性株(P均<0.05)。结论曼氏血吸虫雌雄尾蚴对吡喹酮的敏感性存在差异，雄性尾蚴敏感性高于雌性。曼氏血吸虫吡喹酮抗性的产生与雄虫对吡喹酮的敏感性降低有关。