血吸虫对吡喹酮抗药性的研究Ⅶ曼氏血吸虫吡喹酮抗性株与敏感株某些生物学特性

目的 探讨因吡喹酮抗性产生而导致曼氏血吸虫抗性虫株繁殖力发生改变的可能性。方法 以抗性株与敏感株毛蚴和尾蚴定量感染光滑双脐螺和CD，小鼠，宿主体内观察比较曼氏虹吸虫吡喹酮抗性株和敏感株生物学特性：对螺感染率、感染性螺存活期、在螺体内产尾蚴量、尾蚴和虫卵开放前期及虫卵孵化率。结果单只螺暴露于单个毛蚴2h，抗性株与敏感株对螺感染率为19．8％和8．9％，两者间差异有非常显著性(P=0．006)；逸蚴期间，塞内加尔抗性株感染螺存活率高于敏感株；用塞内加尔抗性株和敏感株毛蚴感染所获阳性螺产尾蚴量(尾蚴／螺)为6875条和14611条；塞内加尔抗性株和敏感株尾蚴开放前期为32．2d和27．7d。抗性株与敏感株鼠体内虫卵开放前期为42．8d和45．5d；虫卵孵化率为80．9％和78．0％。结论 曼氏血吸虫吡喹酮抗性株对实验室传代的光滑双脐螺具有高感染性，此生物学改变似与吡喹酮抗性产生相关；塞内加尔抗性株与敏感株问存在其他变化则被认为是曼氏血吸虫不同地理株间的差异。

STUDIES ON RESISTANCE OF SCHISTOSOMA TO PRAZIQUANTEL Ⅶ. SOME BIOLOGICAL CHARACTERISTICS OF PRAZIQUANTEL-RESISTANT AND -SUSCEPTIBLE ISOLATES OF SCHISTOSOMA MANSONI

Objective To investigate if there is a change in the fecundity of Schistosoma mansoni associated with the development of the resistance to praziquantel. Methods The biological characteristics of four praziquantel-resistant isolates and three praziquantel-susceptible isolates of S. man-soni were compared in Biomphalaria glabrata snails and outbred CD1 albino mice. Results When snails were exposed to a single miracidium per snail for 2 h the infection rate of the snails in resistant isolates was 19. 8% , while that in susceptible isolates was only 8. 9%. There was a significant difference(P =0. 006) between the resistant and susceptible isolates. The survival rates of the snails infected with Senegalese isolates , which have been shown to praziquantel-resistant, during the cer-carial shedding period, were longer than those of the susceptible. The total number of cercariae shed from each snail infected with a single miracidium from the three Senegalese isolates was 6 875, while that from the susceptible isolates was 14 611. The prepatent period of cercariae of Senegalese isolates was 32. 2 d , while that of the susceptible isolates 27.7 d. The respective prepatent periods of the eggs of the resistant and susceptible isolates as measured by appearance of eggs in faeces in mice were 42. 8 d and 45. 5 d. The hatching rates of the eggs collected from the mice infected with the resistant and susceptible isolates were 80.9% and 78. 0%. Conclusion The high infection rate of B. glabrata snails with resistant isolates is considered as the change connected with praziquantel resistance possibly, and the differences were found between the Senegaleses resistant and susceptible isolates could represent the differences between various geographic isolates of S. mansoni.