血吸虫病,是由於血吸虫盘踞在人的肝肠血管系统里而引起的。这种病流行在长江下游沿岸及其以南的广大农村中。血吸虫产生的卵,从人的大便中排出体外,如果这种有血吸虫卵的大便流入河里或池塘里,卵在水中就孵化一种全身有毛的小虫,叫做毛蚴。毛蚴在河里或水田里,遇到了钉螺蛳(一种较海蛳还小如鞋钉样的螺蛳),就钻进了钉螺蛳的体内,经过一个多月的时间,就会生长成许多有尾巴的小虫,叫做尾蚴。之後,这些尾蚴从钉螺蛳体内钻出来(尾蚴小到肉眼看不见),遇到人 Schistosomiasis is caused by schistosomiasis entrenched in the liver’s intestinal vascular system. The disease is endemic in the lower reaches of the Yangtze River and in the vast rural areas south of it. Eggs produced by schistosomiasis are excreted from human bowel movements. If stools with schistosomiasis eggs flow into the river or pond, the eggs hatch a hairy worm in the water, called maggots. In the river or in the paddy field, the raccoon encounters snails (a type of snail that is smaller than a jellyfish) and drills into the body of a snail. After more than a month, it will grow into many things. The tail worm is called tail lice. Afterwards, these tail pluckers come out of the snails (the tails are small enough to be invisible to the naked eye) and encounter people.