Johne's Disease - An Introduction
Johne’s disease (JD) in cattle is caused by a bacterial infection. The name of the bacterium is ‘Mycobacterium avium sub-species paratuberculosis’ which is more commonly referred to as ‘Map’.
Initially the bacteria live in the gut of infected cattle where they grow and slowly cause damage. Once the disease progresses, the bacteria spread to other parts of the body including the udder, womb and lymph nodes.
Importantly, Map does not always infect an animal after exposure. When infection does occur, the clinical signs of disease do not occur immediately.
Signs of Johne’s disease are typically seen in animals that are between 3 and 5 years old but can occasionally be seen in animals that are younger than two years of age.
The typical signs include:
- weight-loss despite a good appetite
- scour (not bloody)
- soft swelling of the jaw (bottle jaw) or brisket
As the animal gets older, the signs become more obvious. An infected animal may also suffer reduced production, reduced fertility performance and increased susceptibility to other disease before the obvious signs occur.