Johnes disease is an incurable bacterial disease that affects the intestines of sheep, goats, deer and cattle, causing the intestinal walls to slowly thicken reducing absorption of nutrients.
There is a production loss and reduced feed conversion efficiency from the initial infection leading to severe weight loss and death.
Lambs can contract Johnes disease from a very young age when they start grazing. Younger animals are more susceptible to infection than older animals. Infections are generally picked up from contaminated pastures, but because the incubation period is very long, clinical signs are not seen until later in life.
There is no treatment for Johnes disease, so prevention by vaccination is important.