There are two categories of sheep with Johne's disease: clinically diseased sheep and subclinically diseased sheep. Listed below are the categories that subclinically diseased sheep fall into:
1. Sheep that are exposed to/infected with Johne's disease but not shedding
bacteria and are blood test negative
2. Sheep that are shedding bacteria but are blood test negative
3. Sheep that are shedding bacteria and are blood test positive
4. Sheep that appear thinner, are shedding bacteria and are blood test positive
Sheep in 1 through 4 all appear healthy.