Johne's disease: how to spot and report the disease
Advice on what to do if you suspect there is an outbreak of this infectious disease.
Identifying Johne's disease
It may be years after infection before an infected animal becomes ill. Johnes’s disease can be identified through blood samples or PCR testing on dung samples. It should be noted, however, that that infected animals do not always test positive, especially in earlier stages of infection. Therefore, testing should be appreciated at herd or group level, rather than individual animals, and this is an example of where your vet’s advice is critical to understand the risk in your herd.
Signs of the disease are rarely seen before two to three years of age. Generally, there is a period of reduced milk output or fertility well before the animals begin to show signs of advanced disease.
The signs of advanced disease include:
- persistent and profuse diarrhoea
- significant weight loss
These signs are seen most commonly in animals at three to five years of age. After disease has developed the diagnosis can usually be confirmed through PCR tests from a dung sample.