羊在日本血吸虫病传播中的作用Ⅲ羊粪对环境的污染及血吸虫感染高危环境预测

Role of goat in transmission of schistosomiasis japonica Ⅲ Environmental contamination by goat feces and prediction of environments at high risk of S. japonicum infection

目的定量估算敞放散养的日本血吸虫感染性山羊粪便对江滩环境的污染范围和面积,为科学评估散养山羊在日本血吸虫病传播中的作用及制定防控措施提供理论依据。方法采用自制羊粪收集背袋收集每只感染性山羊白天(12 h)排放的全部粪便,称重并统计羊粪颗粒数。采用插卡式多功能轨迹记录器现场记录敞放散养山羊白天在江滩游走采食的活动轨迹和速度,推算羊粪污染江滩的最大范围,估算羊粪中虫卵孵化出的毛蚴可感染环境中钉螺的最大面积。结果敞放散养的日本血吸虫感染性山羊白天(12 h)在江滩采食游走过程中的平均排粪量为(232.8±39.8)g/只,每只山羊白天排出的粪便由(819.2±152.1)颗粪粒构成;山羊平均游走速度为(0.522 7±0.099 7)km/h,白天按12 h计算最长往返距离平均为(6.272 4±1.195 8)km;山羊白天游走的最大活动半径为3.136 2 km,最大活动范围(即粪便可污染江滩的最大面积)平均为(3 191.113 0±1 189.709 4)hm^2,推算羊粪中虫卵孵出的毛蚴可感染钉螺的面积(即需要重点查/灭感染性钉螺的范围)平均为(3 210.717 5±1 190.907 3)hm^2。结论敞放散养在江滩上的日本血吸虫感染性山羊排出的粪便中所含血吸虫虫卵对环境的污染强度与感染性山羊数量有关;有固定过夜羊舍的敞放散养羊群粪便对江滩的污染范围相对稳定在白天游走范围内。羊粪对江滩的污染范围与山羊养殖户数及羊舍分布有关;羊粪中血吸虫卵孵化出毛蚴可感染钉螺的面积大于羊粪中虫卵的污染面积,即查、灭感染性钉螺范围大于发现羊粪的范围。

Objective To quantitatively estimate the range and area of environmental contamination by the feces of Schistosoma japonicum-infected that were freely grazed,so as to provide the theoretical evidence for the scientific assessment of the role of the freely grazed goat in the transmission of schistosomiasis japonica and development of control strategy. Methods All the fecal samples excreted by the infected goat at daytime（12 h）were collected by using a self-made goat fecal collector,weighed and counted. The quantity and dispersal of the feces excreted by the freely grazed goat at daytime under a natural condition were investigated,and the walking route and speed of the freely grazed goat at daytime were recorded with a multifunction GPS data logger. The maximum range and area of the environment contaminated by the feces of the freely grazed goat at daytime were estimated,and the maximum range and area of the Oncomelania hupensis snails that may be infected by the schistosome miracidium released from the eggs in the fecal samples of the freely graze goat at daytime were calculated. Results During the walking along the marshland at daytime（12 h）,the quantity of the feces execrated by the freely grazed infected goat was（232.8 ± 39.8）g per goat,and the fecal samples were composed of（819.2 ± 152.1）pellets. The goat had a mean walking speed of（0.522 7 ±0.099 7）km/h,and the longest distance,largest radius and largest range of walking activity were（6.272 4 ± 1.195 8）km,3.136 2 km and（3 191.113 0 ± 1 189.709 4）hm2at daytime,respectively. The area of the snails that may be infected by the miracidium released from the eggs in the fecal samples of the freely graze goat（range of key regions for infected snails detection and control）at daytime was estimated to be（3 210.717 5 ± 1 190.907 3）hm2. Conclusions The intensity of environmental contamination by the eggs in the fecal samples of the freely grazed goat is linked to the number of infected goat. The contamination range caused by the feces of the freely grazed goat with fixed fences is relatively stably kept within the walking range at daytime,and the range and area of goat fecal contamination is associated with the number of households that breed goat and the distribution of goat fence. The area of the snails that may be infected by the miracidium released from the eggs in the fecal samples of the freely graze goat is larger than the area of setting contaminated by the eggs in the goat feces,indicating that the range of infected snail examination and control is larger than the range of goat feces detected.