I was wondering if Bovine TB affects all ruminant mammals or just domesticated cattle? There is such blizzard of confused infomation at the present, but have not heard of any deer populations being (allegedly) infected.
There is a lot of confusing stuff about it.
I have always thought that something that eats a similar diet to domestic cattle would be the spreader.
I think Badgers are wrongly blamed because they eat food that has been in the fields that are contaminated with it and so would test positive for a while. The cattle would have it first and the badgers would only test after browsing in the contaminated grass. Deer are more likely to carry it in a multiplying form that would spread to other cattle because they are more like cattle.
Is certainly found in other species - badgers, deer, goats, pigs, camelids (llamas and alcapas), dogs and cats are all confirmed hosts.
The latest British Wildlife references a report in Mammal Review 2011,41:175-196, which has estimated that a deer population in excess of 25 Fallow or 91 Roe/Red animals per 100ha can maintain Bovine TB infection. In other words, fallows are more prone, it seems.
The badger issue has, I suspect, become a hobby horse in some areas. I have heard farmers tell (possibly exaggerated) tales of equipment up to the size of combine harvesters disappearing into badger setts. I think to many it has become a point of principle, divorced from scientific fact, to see the badger culls proceed or be stopped.
It is like humans. A vet would test positive for it for the time it took his/her immune system takes to eliminate it. The badgers are doing the same when they browse for invertebrates under dung from infected animals and will show a background count for a day or so as a result. It will never be in a spreading or multiplying form like this. As a large part of there diet is browsed from land with infected cattle on it there will always be a background count of the pathogen there. In order to get a reliable result from the scientific data the badgers would have to be relocated to a "clean room" and tested many times with a control population that is in non contaminated land and a further group on contaminated land. The science would be meaningless without this being done.
I would only bother with animals that are known to show symptoms for research if i was paying the lab fees!