OJD: Implications for Neighbours and Traces from Infected Flocks

Note Number: AG1253
Published: August 2006
Updated: September 2009

This Agriculture Note explains why it means to be a neighbour or a trace to a flock where ovine Johne’s disease (OJD) has been confirmed.

Flocks that have sold sheep to, or purchased sheep from, or that are neighbours to OJD infected flocks are routinely advised of this association by the owner of the infected flock.

It then becomes the responsibility of the owner of the traced or neighbouring flock to determine the likelihood that their flock is infected. DPI or private veterinary practitioners can assist by performing a risk assessment and providing advice on managing and/or preventing OJD.

Owners of neighbouring or traced flocks should consider the following issues.

Determine the risk that your flock is infected

It may initially come as a shock to some farmers when they are linked to an infected flock. Determining the likelihood that the flock is infected can start by the owner asking questions such as ‘do I have any unexplained thin sheep?’ or ‘has my flock mortality rate increased over the last few years?’ or ‘is there a significant tail in any mobs?’. If the answer is yes to any of these questions, then further investigation is warranted. Johne’s disease is an insidious disease and clinical signs in a flock may appear gradually and over a number of years.

Other questions to ask are:

• Do my neighbours farm sheep?
• Are my boundary fences sheep-proof?
• Is there water run-off from neighbouring sheep properties onto my land?
• Have I agisted sheep?
• How regularly do I buy-in sheep?
• Where have I purchased sheep from?

The answers to these questions will give a fuller appreciation of the risks the flock has faced.

It is strongly recommended that owners of flocks that are linked to an infected flock seek advice from their private veterinarian or DPI animal health staff. These professionals can help assess the risk that the flock is infected with OJD.

DPI staff are available to perform post mortem examination on a small number of thin or emaciated sheep (if present) in order to assist establish if infection is present in the flock. Private veterinarians can also perform post mortem examinations or, if the owner of the flock chooses, pooled faecal culture tests on the flock. By using these tests suspicion can usually be resolved.

Commence vaccinating against OJD

DPI strongly recommends that all flocks neighbouring or traced to an OJD infected flock vaccinate against OJD. Replacement lambs should be vaccinated between 4 and 16 weeks of age. One vaccination lasts for the sheep’s lifetime.

Older sheep can be vaccinated to reduce the development of clinical disease and deaths. The cost effectiveness of vaccinating older sheep may be taken into consideration.

Further information about vaccinating sheep against OJD is contained in the Agriculture Note ‘Vaccinating sheep against ovine Johne’s disease’.

The Assurance Based Credit (ABC) Scheme and Sheep Health Statement

The ABC Scheme operates throughout Australia. Sheep for sale have an ABC score which indicates the risk that the sheep are infected with OJD. The higher the ABC score (1-10) the lower the risk. Most sheep in Victoria are not known or suspected to be infected with OJD and are entitled to an ABC score of 3. If the owner of a flock suspects that OJD may be present in the flock, they must provide any purchaser with a Sheep Health Statement, and must only claim 0 credit points in Category A of the Sheep Health Statement (i.e. unless the flock has been tested or vaccinated against OJD, the flock’s ABC Score should be 0). They may claim extra points for vaccination and/or testing (if a tested low level infected flock).

It is important to remember that a Sheep Health Statement is a legal document and penalties apply for incorrect completion. Refer to Table 1 for opportunities to sell sheep from a flock that is infected or suspected to be infected with OJD.

When OJD is confirmed in a flock

If OJD is confirmed in a flock, DPI officers will assist in developing a Property Disease Management Program (PDMP) with the flock owner and private veterinarian or consultant. Vaccination is the key to controlling OJD in a flock. Financial assistance is available to assist owners to manage OJD in Victoria (refer Agriculture Note ‘Financial assistance measures for ovine Johne’s disease in Victoria’).

Table 1. Options for selling sheep from flocks with 0 credit points in Category A of the ABC Score (i.e. flocks infected and suspected to be infected)

* Sheep showing clinical signs consistent with OJD should be destroyed on-farm or sent directly to a knackery. They must not be sold for human consumption.

** ABC score 0 store terminal lambs must be identified with an NLIS ‘T-tag’

*** Pens of ABC score 1 non-slaughter sheep must show the ABC score on the sale pen prior to and during the sale (ie. orange pen sticker).

All non-slaughter sheep from flocks with 0 credits in Category A of the ABC score, must be sold with a Sheep Health Statement (Sections 3 and 4 are optional for sheep movements within Victoria).

Further information

Further information about OJD can be obtained by contacting your local SheepMAP veterinarian, animal health staff at your nearest DPI office or by visiting the DPI website.

Acknowledgements

This Agriculture Note was developed by Dr Alison Lee, Biosecurity Victoria – Animal Standards Branch Sept 2006.

It was reviewed by Dr David Champness, Biosecurity Victoria – Animal Standards Branch Sept 2009.