西昌市邛海周边地区血吸虫自然疫水感染调查

目的了解西昌市邛海周边地区地形、地貌、疫水来源、感染性钉螺分布等因素与居民血吸虫病感染之间的关系.方法根据全球卫星定位系统(GPS)测绘图及钉螺调查结果,在西昌市邛海周边4个乡,选择196个点进行疫水测定.小鼠每日上下午各接触疫水1h,连续5d共10h,饲养35d后解剖,了解感染情况.结果人群平均感染率与测定点阳性率间存在正相关(0.05＞P＞0.02),阳性点的分布在地理特征上也呈现出一定的规律性.居民区疫水测定点阳性率与人群感染率相符,感染程度越重的村受外来水源的影响越大,汇水地形感染点感染率极高.在人群感染率较低的村,疫水测定结果与阳性钉螺水系分布符合率都高;而在人群感染率高的地区,则出现疫水测定阳性点与发现阳性钉螺水系感染点符合率极高而疫水测定阴性点与未发现阳性钉螺水系感染点符合率极低的情况.结论疫水测定结果表明,在梯地、阶地所占面积大的村,哨鼠感染率高,人群感染率也高;平地所占面积大的村,哨鼠感染阳性率低,人群感染率也低.在开展血吸虫病防治时应重视外来水源的影响,扩大防治范围,也应重视居民区附近的血吸虫病防治,在高感染地区必须在钉螺调查的基础上结合疫水测定结果才能更为准确地判断该地区水体污染程度.

Investigation of Water Contaminating Situation in Qionghai Lake Area, Xichang City, Sichuan Province

Objective To understand the water contaminating situation and relationship among topography, landforms, irrigation system, distribution of infected snail and the human infection of schistosomiasis japonica in Qionghai Lake area, Xichang City. Methods Mice bioassay was carried out in 196 sites selected from 20 demonstration villager groups with different human infections of the area based on GPS(global positioning systems) digitized map and the snail survey results. The sentry mice were exposed in water 1 hour every morning and afternoon for successive 5 days and dissected 35 days after last exposure. Results There were higher correlation between average human infection rate and the positive rate of mice bioassay sites ( 0.05>P>0.02 ) and the distribution of positive mice bioassay sites revealed certain geographical patterns. In resident areas, the positive rate of mice bioassay sites coincided with the human infections. In villages with higher human infections, the positive results of mice bioassay were greatly under the influence of the irrigation system coming from the outside villages. The confluence sites were usually with higher sentry mice infection rate than that in anywhere else. The positive sites of mice bioassay were highly agreed with the distribution of infected snail in villages with higher or lower human infection rates. But in villages with higher human infection rates, the number of negative sites of mice bioassay were less than number of the sites without infected snail, or in other words, in sites without infected snail, higher frequency of positive mice bioassay was detected. Conclusions In Qionghai Lake area, Xichang City, the higher positive rate of mice bioassay and human infection rate were detected in villages with more hills and terrace, while they were lower in villages with more flatland. In carrying out control measures in such areas, great attention should be paid to the impact of irrigation system coming from the outside villages, i.e. the extend of actual control program should not be limited only within the resident areas. In areas with higher human infection rate, the water pollution situation should be evaluated by both mice bioassay and snail survey.