It is not known whether bovine spongiform encephalopathy (BSE), a disease of cattle invariably deadly to them, can be transmitted directly from one infected animal to another at all stages of the infection  If it can be, there is now a reservoir of infected cattle incubating the disease  There are no diagnostic tests to identify infected animals before the animals show overt symptoms
Ttherefore, if such direct transmission occurs, the disease cannot be eradicated by
removing from the herd and destroying any diseased animal as soon as it shows the typical symptoms of advanced BSE