Sorry to start with these shocking images but it is important to see the damage Tb does, as you read on you will see these pictures are of an animal that tested negative to the skin test TWICE. The cheese-like substance is BTb.
This case history has been reproduced with the kind permission of the owner.
The above animal displayed no outward symptoms of Tb, he weighed 83kg on PM, but luckily the owner knew that the skin test is unreliable. She had the animal X-rayed which showed up lesions, this animal was therefore highly infectious so she agreed to it being culled.
This is a common finding - no outward signs but highly infectious. This disease can easily be passed on via shows, on-farm matings etc. and yet to date there is no reliable test.