北移传代钉螺在北方生存的纵向观察及其对血吸虫的易感性

SURVIVAL OF ONCOMELANIA HUPENSIS SNAILS IN THE NORTH OF CHINA AND THEIR SUSCEPTIBILITY TO SCHISTOSOMA JAPONICUM

目的 进一步评价因南水北调将钉螺迁移至北纬 33°15′以北地区后 ,钉螺的生存繁殖力及对血吸虫的易感性。方法 采用现场螺笼放养定期观察的方法 ,对已移至江苏徐州岱山传代 3年的钉螺在北方的存活率作了为期 5年的纵向观察 ,并在岱山以血吸虫毛蚴对其进行了实验性感染。 结果 钉螺在山东济宁 1年后存活率为 0 ;徐州岱山第 4、5、6、7和8年的存活率依次为 34.76 %、16 .93%、6 .17%、0 .74 %和 0 ;在对照区镇江高资钉螺的存活率分别为 71.6 7%、6 8.38%、6 0 .5 4 %、5 8.4 2 %和 5 6 .72 %。幼螺成活率 ,山东济宁、徐州岱山和镇江高资分别为 0、13.6 7%和 83.0 0 %。钉螺与毛蚴感染比例分别为 1:5、1:2 0和 1:4 0时 ,北移钉螺感染率分别为 14 .89%、6 5 .96 %和 6 2 .2 2 % ,对照区钉螺则为 16 .84 %、5 6 .2 5 %和 6 9.4 1% ,差异无显著性。 结论 可将我国大陆北纬 33°2 3′以北地区列为钉螺非孳生地区 ,33°2 3′至 33°15′列为非适宜孳生地区。南水北调将钉螺移至非孳生区 ,钉螺则不能存活 ;移至非适宜孳生区 ,钉螺因不能适应环境其生存与繁殖力逐年下降 ,呈逐渐消失趋势 ,但残存钉螺仍保持对血吸虫的易感性。

Objective To evaluate the survival of Oncomelania hupensis snails following their transfer north of 33°15′north latitude with construction of South to Northern Water Diversion Project of China and their susceptibility to Schistosoma japonicum . MethodsThe observations were made on the survival rates of the snails fed in Xuzhou for three years, in Jining, Shandong Province (35°23′north latitude) and Xuzhou, Jiangsu Province (34°21′north latitude) over five years and the susceptibility of the snails to the miracidia of S. japonicum in Xuzhou. Results The first year survival rate for snails transferred to Jining was 0. The survival rates for year 4, 5, 6, 7 and 8 in snail maintained in Xuzhou were 34.76%?16.93%?6.17%?0.74% and 0 respectively. This compares with survival rates of 71.67%?68.38%?60.54%?58.42% and 56.72% for snails maintained in Zhengjiang, Jiangsu Province (32°10′north latitude) which is the natural location of the snails. The survival rates of young snails in Jining, Xuzhou and Zhengjiang were 0, 13.67 % and 83.00% respectively. A comparison of infection rates with the proportions of snail to miracidium of 1∶5, 1∶20 and 1∶40 gave 14.89%, 65.96% and 62.22% for snails fed in Xuzhou, and 16.84%, 56.25% and 69.41% for the control group. There was no significant difference between two groups. Conclusion While snails can survival in Xuzhou they are unable to survival in Jining. There survival time in Xuzhou is limited to a period of eight years but during this period they are equally as susceptible to Schistosoma infection as control snails.