长江无螺江滩的水土对钉螺孳生影响的研究

目的 探索长江南通、如皋段江滩长期无钉螺孽生的原因及该地区的血吸虫病防治对策。方法 采集长江如皋江滩研究段及扬州江滩对照段的水、土样，比较两的理化性质；调查分析两水有无差异；用两的水土室内饲养钉螺，比较分析两的钉螺半年存活率及雌螺的产卵率、螺卵的孵化率，在研究段现场人工控制饲养钉螺，观察存活率。结果 研究段江水的Ca 、总硬度、Mg 氯化物和土样的SO4^2-均显高于对照段，两钉螺半年存活率及雌螺产卵率均无显性差异；研究段通过人工控制能孽生钉螺。结论 海潮顶托能阻止钉螺向下游扩散；今后研究段可停止查螺或只花极少量经费监测，以减少卫生资源的浪费。

Effect of water and soil of marshilands along Changjiang river without snails on snails growth

Objective To explore the reason of no snails growing in long term in the marshilands along Changjiang river Nantong Rugao section and to explore the Shistosomiasis control strategies.Methods Sample of water and soil from Changjiang River Rugao section contrasting Yangzhou section was collected.Physical and chemical character of the two places was compared and analyzed.Hydrologic factor was investigated and analyzed.Snails were respectively breeded with water and soil of the two section in the room.The snails livability of the two in half a year was compared.Ratio of trigamous snails laying eggs and ratio of eggs hatching out was analyzed.Snails were breeded under control in the researched section and the snails livability was observed.Results The Ca+{++},Mg+{++},total rigidity and chloride of water and SO+{2-}-4 of soil from researched section was remarkable higher than that from contrasting section; the snails livability in half a year and the ratio of trigamous snails laying eggs of the two had no remarkable difference.Snails can grow in the researched section by artificial control.Conclusion Tide-topping can obstruct snails spreading towards lower reaches of the river;Inspecting snails can be stopped to monitor it in the researched section with reduced cost,which would save health resources.