It’s always useful to keep a watching brief on learnings from other industries to assist us in keeping a focus on our own biosecurity efforts. In this edition we look at the management of the endemic sheep disease Ovine Johne’s Disease or OJD in South Australia.

Ovine Johne’s Disease (OJD) is an incurable wasting disease of sheep caused by the bacteria Mycobacterium avium paratuberculosis (MAP).

It has a long incubation period from exposure to infection – up to two years, and subsequent onset of clinical signs, making it an extremely difficult disease to detect early and manage.

The MAP bacteria can last for long periods in pastures and soil without sheep being present, which further complicates the ability to control the disease.

While endemic in South Australia, OJD more commonly shows up in wet areas of the state with higher stocking rates. OJD is a notifiable disease and must be reported to the Animal Health team at the Department of Primary Industries and Regions South Australia (PIRSA).

To reduce the economic impact of OJD in sheep and aid sheep producers in managing the disease in SA, PIRSA administers the South Australian OJD Management Program that is supported and funded through the Sheep Industry Fund.

South Australian Chief Veterinary Officer, Dr Mary Carr said the program encourages producers to have their private veterinarian undertake disease investigations for wasting and mortality issues, consider the proactive use of vaccination and consider the risk OJD may pose before introducing animals to their property.

“Movement restrictions relating to OJD for sheep entering SA or moving within SA are no longer in place, which means onus is now on individuals sourcing sheep need to be vigilant when determining what to purchase,” she said.

Earlier this year, PIRSA received reports of the disease on five properties in connection to a consignment from Western Australia. This could have been prevented if producers had practiced good biosecurity.

“Such incidences emphasise why producers need to ensure not only good on-farm biosecurity practices but be fully aware of the requirements that need to be met when purchasing sheep from interstate,” Dr Carr said.

Producers are recommended to:

  • Obtain the mandatory National Vendor Declaration and National Sheep Health Declaration and review them prior to purchase (these documents are compulsory for all sheep entering and moving within South Australia).
  • Consider the economic impact that OJD poses to their business and undertake the necessary precautions for this. Speak to your animal health advisor before buying sheep if you are not sure what infection with OJD means for your business.
  • Seek out vaccinated sheep or vaccinate purchased stock on arrival. If you are introducing vaccinated sheep, you should also consider vaccinating your own flock, especially if you are in a high rainfall area.
  • Ask for property accreditations
    • The Australian Johne’s Disease Market Assurance Programs for sheep (SheepMAP) is part of the national effort to manage Johne’s disease in the Australian sheep flock. This is a voluntary program for producers which enable them to identify and promote their low risk Johne’s disease status to their clients. Flocks in SheepMAP are not accredited as free of Johne’s disease, but they have a low risk of disease occurring compared to Not-Assessed flocks.
  • Always ask specific questions of the vendor to gauge risk. For example, ask for evidence that OJD does not occur on the property, what testing or abattoir surveillance has been undertaken, what biosecurity practices prevent introduction of OJD and for how many years has this been in place.
  • Continually monitor the health of the sheep you purchase and report anything unusual.
  • Keep animals isolated on arrival from the rest of your flock – which means not grazing other animals on the same land as the new flock.

Many South Australian producers who have had OJD detected in their flocks have been adhering to documented Property Disease Management Plans (PDMP) formulated in consultation with the Department’s animal health advisers, in order to manage disease on their properties and flocks.

PDMPs can provide a pathway to manage OJD for a property and flock if followed closely. Without undertaking a total destock, these are long-term plans that use a combination of flock management, vaccination, and a policy of only sourcing low-risk introductions to achieve the aim of reducing OJD to an undetectable level.

Animal health advisers at PIRSA can help producers manage both the risks of OJD when purchasing animals, and how to manage disease on their property.

For further information on OJD management in South Australia visit the Johne’s disease in sheep page on the PIRSA website or contact your nearest animal health adviser.

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