非螺区输入钉螺分布及扩散规律的初步观察

目的了解输入钉螺的分布及扩散规律,为制定钉螺监测技术方案提供科学依据。方法选择约666 m^2的荒地,用宽50 cm、深30 cm的水沟按棋盘分布分隔成约2 m^2的方块,在一端的一块输入活钉螺1 600只,逐月抽样查螺观察有螺框率、活钉螺密度、幼螺密度、交配、分布距离、天气、温湿度等。结果2008年3～12月观察期间,有螺框率在20.00%～38.18%之间;晴天与阴雨天有螺框出现率分别为22.88%和29.24%,差异有统计学意义（χ^2=4.113,P〈0.05）;荒地台地和小水沟边/底的有螺框率分别为9.38%和35.99%,差异有统计学意义（χ^2=67.246,P〈0.01）,显示有螺框查出率与天气、环境等密切相关。9个月的观察期,有螺框钉螺、活钉螺、2代幼螺密度变化范围分别在2.17～5.71只/框、2.03～5.54只/框和0～4.56只/框之间,活钉螺、2代幼螺密度荒地台地明显低于小水沟边/底,分别为1.22只/框、0.78只/框和3.72只/框、2.82只/框;推算钉螺输入繁殖的2代钉螺生长至成熟可交配的钉螺的时间仅为5个月。观察期间,在第3条小水沟外未查获钉螺,单向扩散距离最远为4.5 m。结论钉螺主要分布在荒地有水区边缘如水氹、水沟边／底等潮湿、水分充足的地方，并沿水沟边扩散为主；输入钉螺阴雨天较活跃，查出率较高。

Preliminary observation of imported Oncomelania hupensis distribution and diffusion regularity in areas without snails

Objective To understand the distribution and diffusion regularity of Oncomelania and formulate techniques and provide scientific support for Oncomelania monitoring.Methods Ditches 50 cm wide × 30 cm deep were used to square off 666 m2 of unused land in a chessboard pattern at intervals of 2 m2;1 600 imported snails were observed in a certain plot,and the monthly percentage of squares with snails,density of living snails,density of young snails,mating,distribution distance,weather, temperature,humidity, etc.were observed. Result From March to December 2008,the percentage of squares with snails was between 20.00%--38. 18%;this percentage was 22.88% for sunny days and 29.24% for cloudy and rainy days（x^2=4, 1l3,P〈0.05）and 9.38% for unused land and terraces and 35.99% for the sides or bottom of ditches（x^2= 67. 246, P〈0. 01）. The percentage of squares with snails was closely related to the weather and environment. Theas indicated by 9 months of observation, changes in squares with snails ranged from 2.17-- 5.71 snails/square and changes in the density of living snails and young snails of the second generation ranged from 2.03 --5.54 snails/square and 0--4.56 snails/square. There were markedly fewer living snails and young snails of the second generation in unused land and terraces than on the sides or bottom of ditches （1.22 and 0.78 snails/square vs. 3.72 and 2.82 snails/square）. Calculations indicated that Oncomelania took 5 months to enter and produce a second generation mature enough to mate. In the course of observation, snails were not found outside ditch 3, and the farthest distance of unilateral diffusion was 4.5 m. Conclusion Oncomelania was mainly distributed in unused land bordering aquatic areas, e. g. with pools of water, damp areas with adequate moisture such as the sides or bottom of ditches, and along ditches. Imported Oncomelania was active on cloudy and rainy days and was detected rather frequently.