Ovine Johnes Disease

Ovine Johne’s Disease (OJD) is a chronic wasting disease of sheep and goats caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). The infection primarily affects the intestines, gradually reducing an animal’s ability to absorb nutrients. Infected sheep typically lose condition over time despite continuing to eat, often leading to death.

Animals become infected by ingesting the bacteria, usually through contaminated pasture, soil, water, or manure. Young lambs are particularly vulnerable. Once introduced, the bacteria can persist in the environment for extended periods surviving in soil, pastures, and waterways making eradication extremely difficult.

OJD has been detected in New South Wales, Victoria, Tasmania, and South Australia, with varying prevalence across regions. Western Australia, Queensland and the Northern Territory have lower levels or restricted occurrence, but ongoing surveillance remains essential.

In Australia, OJD is a notifiable disease, meaning cases must be reported to government authorities. This ensures appropriate monitoring and control measures are in place to limit its spread.

Testing and Inspection Options

Abattoir surveillance: Producers can request an OJD inspection of sheep being processed, allowing early detection and confirmation.

Laboratory testing: Options include faecal culture and pooled faecal testing, which can identify infected flocks before clinical signs become obvious.

OJD poses a significant economic burden to the sheep industry. Losses result from reduced productivity, poor weight gain, higher mortalities, increased management costs, and impacts on trade and market access. For producers, the presence of OJD can also limit stock movements and reduce sale value.

Current evidence indicates that OJD does not pose a direct food safety risk to humans. However, maintaining strong surveillance and control programs is vital for protecting market confidence in Australian sheepmeat and wool.

Vaccines are available and have proven effective in reducing both the prevalence of infection within flocks and the severity of disease in affected animals. Vaccination programs, combined with good biosecurity practices, remain the most practical long-term tools for managing OJD at the farm level.

Ovine Johne’s Disease is a serious animal health challenge with lasting impacts on productivity and profitability. While it is not a food safety concern, its ability to spread silently within and between flocks makes ongoing vigilance critical. Producers are encouraged to consider vaccination, utilise testing services including abattoir surveillance and work closely with animal health advisors to reduce risk and protect their enterprises.

An E-Learning module on this disease is freely accessible on MINTRAC’s site as part of a suite of training materials developed as part of the National Sheep Health Monitoring Project - OJD E-Learning Course.