the natural system that preventsdiseasesspreading from one type of animal or plant to another. This is often referred to in relation to BSE (=a disease of cows)spreading to humans in the form of CJD (=a brain disease in humans). (阻碍疾病传播的)种间屏障(常在谈及疯牛病以克雅病的形式传染人类时用到)