Hi Novice,
I have never seen Johnes in Roe deer, but certainly in Red deer the disease can be spread through the herd very quickly. The symptoms can be acute or chronic. The symptoms are chronic wasting and most of the time scouring (but not always) in yearlings to old animals. There is typically some hardening of the small intestine, and they have a more crinkled appearance. In Johnes cases I have noticed that in the majority of cases there is quite a lot of clear fluid in the abdominal cavity and a metallic smell.
Not all deer carrying the disease develop the clinical symptoms, and so 'carriers' can exist in the herd for a long time, still spreading the disease but sometimes never developing clinical symptoms. The Johne's Bacteria (Mycobacterium paratuberculosis) can also exist in the soil for quite some time so infected pasture can infect animals (especially calves) that ingest soil in which the bacteria live. Once Johne's is present in a herd - or land -, it can be very difficult to eradicate.
I dont think the disease is passed through the milk into the young, but more likely in the feacal matter usually running down the back legs and around the udder. It was thought the calves picked up the bacteria through this manner.
Johne's can be disguised through good management, and animals can have the disease for months, even years, but when an infected animal is exposed to stress through malnutrition, or stressful handling, the disease can manifest itself very quickly. There was a test available but I believe it was not that reliable back then, whilst it showed up many of the clinically infected animals, it also produced many inconclusives.
In the early to mid 90's we (Lewis Griffiths MRCVS, BVMS, and myself) took many hundreds of blood and feaces samples from red deer and sent them up to the Moredun Research Institute in Scotland. They did a tremendous amount of research into Johne's disease around then, so presumably some research papers will exist from that research. I believe John Fletcher was also working on Johnes at that time, so John could be a good source of quality info.
There may be new research done since Moredun, but I am not aware of it.
Hope that helps.
Best regards,
Mike
Mike Allison
(Managing Director - Jelen Deer Services)