便民河水系血吸虫病潜在流行因素监测Ⅰ钉螺分布与消长

目的掌握便民河水系河道实施砼护坡工程后钉螺变迁、分布及消长规律。方法采用前瞻性研究的方法,2002～2005年每年春季采取系统抽样结合环境抽查法调查水系钉螺分布,比较不同环境钉螺面积、感染性钉螺面积、有螺框出现率、活螺密度和钉螺感染率等螺情指标的逐年变化情况。结果2002～2005年,便民河水系主河道、内陆灌区和相邻江滩的钉螺面积分别在20.94～31.88、39.30～48.08hm^2和275.13～292.31hm^2之间,有螺框出现率分别在9.96%～21.88%、29.61%～58.54%和62.14%～85.97%之间,钉螺平均密度分别在0.97～1.86、0.92～3.96只/0.1m^2和7.72～11.15只/0.1m^2之间,其中2005年便民河水系河道、内陆灌区和通江口外江滩有螺框出现率分别为21.88%、39.33%和83.81%,活螺密度分别为1.30、3.96只/0.1m^2和11.15只/0.1m^2。4年来主河道内有螺框出现率上升较快,内陆灌区钉螺密度增加了4倍,相邻江滩各项螺情指标基本稳定,但江滩有螺框出现率和钉螺平均密度分别是水系内的2～3倍和3～8倍。结论河道内未清理的高滩面是造成水系钉螺迅速回升的主要原因,便民河水系血防工作的重点首先要对高滩面进行切滩清淤,同时要加强内陆灌溉区螺情控制力度,做好通江河口河道的螺情监测和药物灭螺工作。

Surveillance on potential factors influencing schistosomiasis prevalence in water system of Bianmin River Ⅰ Distribution and dynamics of Oncomelania snails

Objective To understand the distribution, variance and dynamics of Oncomelania snails in the water system of the Bianmin River after the river bank being protected with concrete. Methods The snails in the water system of the Bianmin River were investigated with the systemic sampling method and environmental spot-checking method in spring from 2002 to 2005. The indexes including area with snails, area with infected snails, rate of frames with snails, density of living snails and infection rate of snails in different environments were collected, analyzed and compared year by year. Results From 2002 to 2005, in the main river of the water system of the Bianmin River, irrigation areas and the adjacent marshlands of the Yangtze River, the areas with snails were 20. 94-31.88, 39. 30-48. 08 hm^2 and 275.13-292. 31 hm^2 , respectively; the rates of frames with snails were 9. 96%-21. 88%, 29.61%-58. 54% and 62. 14%-85. 97%, respectively; the mean densities of snails were 0. 97-1.86, 0. 92-3. 96 snails/0. 1 m^2 and 7.72-11.15 snails/0. 1 m^2. In 2005, in the main river, irrigation areas and the adjacent marshlands, the rates of frames with snails were 21.88%, 39.33% and 83.81%, respectively; the densities of living snails were 1.30, 3.96 snails/0.1 m^2 and 11.15 snails/0.1 m^2. During the last four years, the rates of frames with snails increased quickly in the main river of the water system of the Bianmin River; the densities of snails increased by 4 times in the irrigation areas; the indexes mentioned above were stable in the adjacent marshlands of the Yangtze River. However, the rate of frames with snails in the marshlands was 2-3 times higher than that in the irrigation areas and the mean density of snails in the marshlands was 3 -8 times higher than that in the irrigation areas. Conclusions The main factor causing the increase of snails is that the river beach has not been cleaned yet in the water system of the Bianmin River, and so the key of schistosomiasis control is that first, the river beach should be cleaned co