We have a cow isolated. She has been scoured for a number of months now, received treatment and still showing no signs of the scour drying up. She is a 10 year old. Always been fertile. Raised a calf this summer. We operate a closed herd and only buy in breeding bulls. Could it be johnes? Can you do an ear notch test for it or is it just blood (can't do milk as she is dry this last month).