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Johne's disease is a chronic wasting disease caused by the bacterium Mycobacterium avium subsp. paratuberculosis. It invariably leads to the death of the animal.
In Australia, Johne's disease has been found in cattle, sheep, goats, deer and camelids.
Johne's disease is a notifiable disease in some states of Australia.
The bacteria that cause Johne's disease live in the animal's intestines and cause thickening of the bowel wall that interferes with normal absorption of food.
There are varying strains of Johne’s disease.
Bovine Johne’s disease (BJD) is generally caused by the ‘C’ strain of the bacteria. BJD affects mainly cattle but also goats, deer and camelids. Ovine Johne’s disease (OJD) is generally caused by the ‘S’ strain of the bacteria. OJD affects mainly sheep but also goats.
Conditions when Johne's disease is likely to occur
The prevalence of Johne's disease varies in different regions of Australia. Information on prevalence zones and the BJD national strategic plan and OJD national management plan can be found on the Animal Health Australia website.
BJD is most common in dairy cattle in south eastern Australia but it can also occur in beef cattle. Western Australia is a BJD-free zone.
There are no OJD-free zones in Australia.
Identification and diagnosis
Diagnosis of Johne's disease will require assistance from a veterinarian.
Clinical signs that would lead you to suspect Johne's disease include:
- progressive weight loss
- emaciation in older animals despite a good appetite
- affected animals may also develop diarrhoea and bottle jaw.
An integrated approach to prevent Johne’s disease should consider the following:
- developing and implementing a farm biosecurity plan
- only purchasing animals with an animal health statement and only introducing low-risk stock onto the property
- implementing grazing management strategies to prevent the spread of the bacteria on-farm
- weaning early to limit infection of young calves, lambs and kids
- vaccinating livestock (vaccines available for both cattle and sheep)