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You are here: Agriculture » Pests, Diseases and Weeds » Animal Diseases » Sheep » Keeping Ovine Johne's Disease out of a Flock

Keeping Ovine Johnes Disease out of a Flock

Note Number: AG0965
Published: September 2006
Updated: January 2011

 

A few simple precautions will significantly reduce the risk of ovine Johnes disease (OJD) entering a flock.

Avoid purchasing infected sheep

The greatest risk of introducing OJD into a flock comes from the introduction of infected sheep. Introduced sheep may initially show no obvious signs of OJD but may be shedding the bacteria in their manure and contaminating pasture. The best way to minimise the risk of introducing OJD is to maintain a closed flock. However, if purchasing sheep, the risk can be minimised by purchasing from low-risk flocks.

The ABC Score

Under the Assurance Based Credits (ABC) Scheme, every mob of sheep in Australia has an ABC score. This score indicates the risk that sheep may have OJD. The higher the ABC score, the lower the risk that the mob has OJD. Purchasing sheep from flocks with a high ABC score means the risk of introducing infected sheep is minimised.  (Refer Agriculture Note: AG1156Assurance Based Credits (ABC) Scheme and the Sheep Health Statement).

Victoria is divided into two Prevalence Areas.

1. Medium Prevalence Area. The following shires are situated in Victoria’s Medium Prevalence Area: Swan Hill, Mildura, West Wimmera, Glenelg, Yarriambiack, Horsham, Gannawarra, Buloke and Hindmarsh. Owners of flocks in these shires can claim 2 credit points in Category A of the ABC score (unless the flock is infected or suspected of being infected).
   
2. High Prevalence Area. The remainder of Victoria is a High Prevalence Area and owners of flocks can claim 0 credit points in Category A of the ABC score.

Flocks that have undergone testing (eg SheepMAP flocks), abattoir monitoring (Abattoir 150 or 500 status), or commenced vaccinating against OJD will have a higher ABC score, and can claim credit points towards the ABC score in Categories B (testing), C (vaccination) and/or D (certified low risk).

Sheep Health Statements

Flocks that have undergone testing (eg SheepMAP flocks), abattoir monitoring (Abattoir 150 or 500 status), or commenced vaccinating against OJD will have a higher ABC score, and can claim credit points towards the Always ask for a Sheep Health Statement (SHS) when purchasing sheep. A SHS requires the vendor to disclose the ABC score of his or her flock. The use of these statements is voluntary, but highly recommended, for all sheep movements within Victoria. However, most states require sheep from interstate to be accompanied by a SHS. Persons making false or misleading statements on a SHS may be liable under Fair Trading legislation and the Stock (Seller Liability and Declarations) Act 1993.ABC score in Categories B (testing), C (vaccination) and/or D (certified low risk).

Avoid introducing OJD by other means

OJD-causing bacteria can also be introduced into a flock in other ways:

Boundary fencing and strays

Owners should make every effort to maintain boundary fencing and gateways in order to minimise the risk of straying sheep. Collect stray sheep and work with neighbours – don’t just put sheep back over a fence. Check mobs and fencing frequently.

 

 

Movement of manure

Run-off from neighbouring properties may carry OJD-causing bacteria into previously uncontaminated paddocks. Diversion drains, double-fenced tree lines, or running cattle in these paddocks may assist in preventing infection in a flock.

Boots and equipment carrying manure have the potential to spread OJD-causing bacteria. Precautions, such as scrubbing boots to remove manure, should be taken to minimise this risk.

Sheep transports and shared facilities

Ensure livestock transport vehicles are thoroughly washed before loading with replacement sheep. Where possible, do not share common stock-handling facilities.

Shows and sales

Precautions to minimise risk of infection with OJD at shows or sales should be observed.  (Refer Agriculture Note: AG1123 Ovine Johne’s disease guidelines for shows and sales).

Other species

Other animal species could spread OJD. Grazing or handling goats and deer separately from sheep is generally recommended, unless there is demonstrated low risk (for example, participation in market assurance programs).

Grazing contaminated land

The bacteria that cause OJD may survive in the environment for 12 months or more.  Producers should consider the risk that land may be contaminated with bacteria prior to purchasing or leasing land, or agisting stock off-farm.

Vaccination

Owners of all sheep flocks should consider whether they should be vaccinating their flock against OJD. Factors to be considered include:

•  their type of enterprise,
• whether they run a closed flock,
• sources of purchased sheep, and
• the risk posed by neighbouring flocks (ie fences and drainage).

It is important to keep in mind that vaccination does not provide complete protection from infection. Vaccinated sheep may still become infected and shed OJD-causing bacteria, allowing spread to other stock. This highlights the importance of ensuring other biosecurity measures are in place.

Further information

Further information about OJD can be obtained from animal health staff at your nearest DPI office or on the DPI web site: http://www.dpi.vic.gov.au/farming/OJD

Acknowledgement

The original authors of this note were Monica Kelly, Richard Keys, and the previous version was published in March 2008.
Reviewed by Rachael Holmes, Biosecurity Victoria. January 2011.