湘江长沙段洲滩钉螺防治后的种群动态

THE POPULATION DYNAMICS OF ONCOMELANIA HUPENSIS AFTER SNAILS CONTROL IN MARSHLANDS IN CHANGSHA SECTION OF XIANG RIVER

采用以系统抽样结合环境抽查的查螺方法,对湘江长沙段洲滩进行连续6年的螺情调查。2003—2008年跟踪调查了湘江长沙段24个洲滩,其中20个洲滩有钉螺分布,占洲滩总数的83.3%,4个洲滩从未查见钉螺。活螺洲滩数分别占当年调查洲滩的62.50%、66.67%、66.67%、70.83%、33.33%、37.50%;2008年与2003年相比,活螺洲滩数下降了40.00%,有螺框出现率、钉螺平均密度、活螺率分别下降了99.10%、99.74%、51.09%。经统计学处理,各洲滩有螺框出现率(Z=91.56,P<0.01)、活螺率(Z=65.13,P<0.01)不相同,但年度下降趋势明显。在20个有螺洲滩中,有感染性钉螺分布的洲滩5个,占有螺洲滩总数的25.00%;有感染性钉螺分布的洲滩逐年减少,平均密度和感染率逐年降低,2007—2008年所有洲滩均无感染性钉螺分布。湘江长沙段有螺洲滩采取的各种防治措施中,药物与环改灭螺相结合的效果远好于单纯的药物灭螺。各种环改灭螺措施中,又以抬洲降滩、翻耕垦种的灭螺效果更持久,更彻底。2007、2008年有螺洲滩数、钉螺总数急剧减少,有螺框出现率、活螺率大幅度下降还可能与水位和气候有关。湘江长沙段洲滩的螺情得到了较好的控制。

Schistosomiasis brings heaps of harmful effects to hosts.It was more widespread in Changjiang drainage basin and Southern China.Oncomelania hupensis,the only intermediate host of Schistosoma japonicum,plays a vital role in the transmission and prevalence of Schistosomiasis.The urban section of Xiang River was considered to be an area without snails.Due to a variety of factors,snails have been found in many marshlands in Changsha section of Xiang River since snails were found in fujiazhou in 1997.To investigate the distribution and quantitative changes of Oncomelania snails in each marshland of Changsha section of Xiang River,and to evaluate the effectiveness of snail control in recent years,we have made a consecutive investigation of snail distribution in marshlands from 2003 to 2008 by using the systematic and environmental sampling according to the methods mentioned in ＂Handbook of Schistosomiasis Control＂.Twenty-four marshlands were investigated continuously from 2003 to 2008.The total number of marshlands with snails were 20 which accounted for 83.3%of all marshlands investigated,and four marshlands had no snails.The number of marshland with living snails accounted for 62.50,66.67,66.6,70.83,33.33 and 37.50% of the year investigated respectively.Compared with 2008,the number of marshlands with living snails,the rate of frame with snails,the average density of snails and the rate of living snails decreased 40.00,99.10,99.74 and 51.09% respectively in 2003.Processed by SAS 9.1.3 Cochran-Armitage Trend Chi-Square Test,the rate of frames with snails（Z= 91.56,P0.01）and the rate of living snails（Z=65.13,P0.01）were different in each marshland,and the downward trend was significant.Among the 20 marshlands with snails,5 marshlands have infected snails,occupying 25.00% of the whole.The number of marshlands with infected snails has declined year by year,so have the average density of infected snails and the infection rate of snails.No marshlands with infected snails were found in Changsha section of Xiang River from 2007 to 2008.The research indicated that the combination of environment improvement and snail control by chemicals was much more effective than only the latter.The effect of snail control was more lasting and more thorough by utilizing higher or lower marshland,reclamation and plantation in all measures of snail control through environment improvement on marshlands in Changsha section of the Xiang River.It may be related to water level and the climate that the number of marshland with snails,the total number of snails,the rate of frames with snails and the rate of living snails decreased sharply in 2007 and 2008.The Oncomelania hupensis in Changsha section of Xiang River have been well controlled.