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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 further evaluate the survival and fertility of Oncomelania snails and its susceptibility to schistosomiasis due to the migration of Oncomelania hupensis to north of 33 ° 15 ’North Latitude by the South-to-North Water Diversion Project. Methods Survival rate of Oncomelania snails that had been transferred to Daishan, Xuzhou, Jiangsu Province for 3 years was observed longitudinally in the north for 5 years by means of on-site observation. The experiment was carried out in Daishan with Schistosoma japonicum miracidia . Results Survival rate of snails in Jining, Shandong province was 0 after one year. Survival rates of Qixian in the 4th, 5th, 6th, 7th and 8th years of Xuzhou were 34.76%, 16.93%, 6.17%, 0.74% and 0 ; Survival rates of high-cost snails in Zhenjiang were 71.6 7%, 6 8.38%, 60.54%, 52.42% and 56.72% in the control area respectively. Young snail survival rate, Shandong Jining, Xuzhou, Daishan and Zhenjiang high capital were 0,13.6 7% and 83.0 0%. Infection rates of Oncomelania and Met magrys were 1: 5, 1: 20 and 1: 40, respectively, and the infection rates of Oncomelania snails were 14.89%, 65.96% and 62.2% respectively, Then 16.84%, 5.62% and 6.441%, respectively, with no significant difference. Conclusion The area north of 33 ° 23 ’north latitude in mainland China can be classified as non-breeding areas for Oncomelania snail and 33 ° 23’ to 33 ° 15 ’as non-suitable breeding areas. The South Water North Project moved the snail to the non-breeding area, and the snail could not survive. When it moved to the non-suitable breeding area, its survival and fertility decreased gradually due to its inability to adapt to the environment, gradually disappearing. However, the surviving snail still maintained its susceptibility to schistosomiasis.