山丘型地区小环境改造后螺情消长情况分析

Analysis of fluctuate of snail conditions after small environment modification in hilly type endemic regions of schistosomiasis

山丘型血吸虫病流行区因地制宜进行沟渠硬化、沼泽地改塘等小环境改造措施后，钉螺面积减少了６６．１６％，活螺密度、活螺框出现率分别下降了７６．５４％及７６．１３％，阳性螺密度下降了１００％；而实施药物灭螺的对照组９年来钉螺面积仅下降了２７．６２％；活螺密度及活螺框出现率分别上升了２６．３５％、１５１．０１％，是小环境改造点的９．８４倍及１１．１３倍。不同环改方法控制螺情的近期及远期效果不一致，以沼泽地改塘效果最稳定，其次为沟底及两侧石砌并用水泥磨面的方法。

Suail areas reduced by 66.16%,density of snail,percent of frames with living snail reduced by 76.54% and 76.13% respectively,density of positive snail reduced by 100% after taking the measuer of small environment modification suitting measures to local conditions in hilly type endemic regions.such as ditch sclerosis and change swamp into pond, et al. But, snail areas only reduced by 27.62%, density of snail, percent of frames with living snail rised by 26.35% and 151.01% respectiovely, 9.84 times and 11.13 times higher than that of modification group respectively,in the last 9 years in control group which took molluscide. The recent and long term effect for snail control was inconsistent among different methods of modification, the effect of changing swamp into pond was the most stable, the next was the method of building ditch with stones and smoothing surface of both sides and bottom with cement.