Changes to Ovine Johne’s Disease (OJD) Prevalence Areas
1. What is ovine Johne’s disease?
OJD is an infectious disease of sheep and goats. It is caused by bacteria called Mycobacterium paratuberculosis. Infected sheep often do not show any obvious signs of disease, although as the disease progresses, they begin to lose condition and will ultimately die. Some sheep will also show signs of scouring but this is not always seen. Often in flocks that have only recently become infected, only a small percentage of sheep have the disease. It can take several years before the presence of the disease becomes evident and the disease impacts significantly on the productivity of a flock. OJD can kill a significant number of sheep in a flock each year unless strategies, such as vaccination, are introduced to limit the impact of the disease.
To access the Information Note, ‘What is OJD?’, please click on the following link http://new.dpi.vic.gov.au/notes/agg/animal-health/ag1126-what-is-ojd
2. What is the OJD Management Plan?
WoolProducers Australia and the Sheepmeat Council of Australia have developed a program to provide a sustainable basis for the management and control of OJD in Australia. The OJD Management Plan (OJDMP) includes the establishment of Prevalence Areas and the use of the ABC Scheme to assist producers who are purchasing sheep assess the risks of the sheep having OJD.
WoolProducers Australia and the Sheepmeat Council of Australia have also agreed to secure further funding for OJD research, and have identified a need for an ongoing communication program.
The OJD Management Committee, comprising representatives from WoolProducers Australia and the Sheepmeat Council of Australia, other key stakeholders nominated by the national sheep industry and Animal Health Australia, meets regularly to review the operation of the OJDMP.
To access more information about the OJD Management Plan please click on the following link http://www.animalhealthaustralia.com.au/programs/jd/ojd.cfm
3. What is the Assurance Based Credits (ABC) Scheme?
The Assurance Based Credits (ABC) Scheme forms the basis of the national Ovine Johne’s Disease (OJD) Management Plan. Every sheep flock in Australia has an ABC score. This score can be used by producers wishing to sell or purchase sheep to indicate the risk of a flock being infected with OJD.
A flock’s ABC score is a measure of the risk of the flock being infected with OJD. It is calculated by adding credits points for the following factors:
- the Prevalence Area in which the flock is located
- the OJD testing history of the flock
- vaccination against OJD
- risk assessment (for infected or suspected to be infected flocks only)
The ABC score of a mob is recorded by the vendor on the Sheep Health Statement. This should be checked by potential purchasers prior to the sale of sheep.
To access more information about the ABC Scheme please click on the following link http://new.dpi.vic.gov.au/notes/agg/animal-health/ag1156-assurance-based-credits-abc-scheme-and-the-sheep-health-statement
4. What are OJD Prevalence Areas?
OJD Prevalence Areas provide an indication of the percentage of flocks that are infected with OJD in a particular region of Australia.
Inspectors employed by Animal Health Australia work in selected abattoirs throughout Australia and examine sheep for signs of OJD as they are being processed. Sheep with signs consistent with OJD are sampled. These samples are sent to a veterinary laboratory and tested for OJD. The OJD Management Committee makes decisions on the boundaries of the various OJD Prevalence Areas based on the information collected by these inspectors.
There are three types of Prevalence Areas. These are:
- Low Prevalence Area:
it is estimated that less than 0.8% of flocks are infected with OJD
- Medium Prevalence Area:
it is estimated that between 0.8-12.5% of flocks are infected with OJD
- High Prevalence Area:
It is estimated that more than 12.5% of flocks are infected with OJD.
OJD Prevalence Areas indicate the risk of infection in a specific area. The risk that a specific mobof sheep is infected with OJD is indicated by its ABC score. The ABC score consists of points allocated to sheep based on: (1) their Prevalence Area, (2) whether they are vaccinated against OJD, (3) whether the sheep have been tested for OJD, and (4) low risk certification (for infected or suspected to be infected flocks only).
For more information about current OJD Prevalence Areas please click on the following link http://new.dpi.vic.gov.au/notes/agg/animal-health/ag1156-assurance-based-credits-abc-scheme-and-the-sheep-health-statement
5. How are OJD Prevalence Areas changing?
OJD Prevalence Areas in some States, including Victoria, will change on 1st January, 2011.
Victoria’s current OJD Prevalence Areas are:
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On 1st January, 2011, Victoria’s Low Prevalence area will be downgraded to a Medium Prevalence Area. The current Medium Prevalence Area will be downgraded to a High Prevalence Area as shown in the map below.
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6. Why are the changes necessary?
Several Prevalence Areas in Australia have exceeded the agreed limits (i.e. 0.8%, or 12.5%) during the last two years of abattoir monitoring. Some Prevalence Areas in NSW have had lower detections than expected. According to national guidelines, Prevalence Areas are reassessed if the agreed limits are exceeded. National industry bodies (Sheepmeat Council of Australia and WoolProducers Australia) have reviewed the current Prevalence Areas and agreement has been reached on the reclassification of Prevalence Areas.
For further information about the changes to Prevalence Areas please click on the following link http://www.animalhealthaustralia.com.au/programs/jd/naojd/ojd_prevalence.cfm
7. When will the changes be introduced?
The changes will be introduced on 1st January, 2011.
8. How will this change affect Victorian sheep flocks?
Flocks that currently claim 4 points for being in Victoria’s Low Prevalence Area will only be able to claim 2 points towards their ABC score when this region is downgraded.
Flocks that currently claim 2 points for being in Victoria’s Medium Prevalence Area will not be able to claim any points (0) for Prevalence Area when the region becomes a High Prevalence Area.
In accordance with the nationally agreed Assurance Based Credits (ABC) Scheme, Nil Assurance flocks in High Prevalence Areas are considered to be the same risk of being infected with OJD as known infected flocks. This is due to the estimated high prevalence of disease in these areas, the insidious nature of the disease and the apparent lateral spread of OJD (i.e. neighbouring flocks are often found to be infected).
There are currently trade and movement restrictions in place for ABC score 0 sheep. Victorian legislation will be altered prior to 1st January, 2011, so all flocks can trade freely within Victoria. As of 1st January, 2011, all sheep (including ABC score 0 sheep) can be moved and traded freely within Victoria. Permits will no longer be required to move ABC score 0 sheep down public roads. Sheep Health Statements will not be mandatory for any flock in Victoria.
9. How do I protect my flock against OJD?
Vaccination and good biosecurity are the keys to protecting your flock against OJD. It is important to understand the ABC score, and how to calculate it for your flock (see below). Ask for a Sheep Health Statement before purchasing sheep. Sheep Health Statements not only provide information about the risk the sheep are infected with OJD, but also provide information about the risk of the sheep having footrot or lice, as well as information on the recent vaccination and drenching history of the sheep.
It is also timely to consider whether you should be vaccinating your flock against OJD. It is strongly recommended that replacement sheep (or those to be sold as replacements) are vaccinated between 4-16 weeks of age. OJD is an insidious disease and you may not be aware that it has been introduced into your flock for months or even years after it’s introduction. Vaccinating sheep against Johne’s disease assists protect your flock against OJD if you inadvertently introduce the disease.
For further information about protecting your flock against OJD please click on the following links http://new.dpi.vic.gov.au/notes/agg/sheep/ag0965keeping-ovine-johne and http://www.farmbiosecurity.com.au/
10. How do I calculate my ABC score?
The ABC score indicates the risk that a mob of sheep is infected with OJD. The lowest ABC score is 0. Sheep with an ABC score of 0 have the highest risk of being infected with OJD. The highest ABC score is 10. Sheep with an ABC score of 10 have the lowest risk of being infected with OJD.
There are four ways to obtain credit points towards your ABC score. These are:
Category A - Prevalence Area credits:
- Flocks in the Low Prevalence Area can claim 4 credits
- Flocks in the Medium Prevalence Area can claim 2 points
- Flocks in the High Prevalence Area can claim 0 points.
(please note that if the sheep are purchased, you can only claim the credits for the lowest PA in which the sheep have grazed)
Category B - Testing credits: credit points can be claimed for testing if your flock is in SheepMAP, you have negative results from abattoir monitoring or you have performed other testing as per the Sheep Health Statement
Category C - Vaccinations credits: sheep must be vaccinated between 4-16 weeks of age or, in the written opinion of a SheepMAP vet, prior to exposure to the Johne’s bacteria to call them Approved Vaccinates and claim credit points for their ABC score.
Category D - Low risk credits: this is relevant to infected and suspected to be infected flocks only).
The back page of the Sheep Health Statement explains how to calculate your flock’s ABC score. You can claim one type of credit from each Category. You then add them together to obtain your final ABC score.
Please remember that a signed Sheep Health Statement is a legal document and penalties apply if a vendor provides false information.
For more information about calculating the ABC score or the Sheep Health Statement, please refer to the Information Note: Assurance Based Credits (ABC) Scheme and the Sheep Health Statement.
To access the Sheep Health Statement please click on the following link http://www.animalhealthaustralia.com.au/shadomx/apps/fms/fmsdownload.cfm?file_uuid=81139B2E-0AD9-8825-D21B-A741FEA2E244&siteName=aahc
11. Can I still trade sheep interstate?
Different States have different entry requirements. Entry requirements are usually based on a minimum ABC score and a Sheep Health Statement accompanying the sheep.
It is possible your sheep may no longer be eligible to enter some States after 1st January, 2011. You may need to take steps to increase your ABC score (i.e. testing or vaccination) before your sheep will be allowed to enter some States. Please refer to the relevant State into which you wish to move sheep for further details.
12. Should I vaccinate my sheep against OJD?
If you breed replacement sheep, it would be wise to vaccinate them against OJD. If you purchase replacement sheep it would be wise to purchase Approved Vaccinate sheep, or vaccinate them upon arrival at your property. If purchasing older sheep, remember that they may have already been exposed to the bacteria that causes OJD, and the vaccine will not be as effective.
The cost of Gudair (the only vaccine currently registered in Australia for the control of OJD) is about $2.00/dose. Keep in mind that each sheep only requires one dose for life.
For more information on vaccinating sheep against OJD, please visit http://new.dpi.vic.gov.au/notes/agg/animal-health/ag1133-vaccinating-sheep-against-ovine-johnes-disease
13. Are Prevalence Areas changing in other states?
Parts of NSW are being downgraded and some parts are being upgraded. Please click on the link to obtain further information regarding the changes to these PAs http://www.dpi.nsw.gov.au/agriculture/livestock/health/specific/sheep/ojd/about/ojd-prevalence-areas-jan2011
Western Australia is currently a Low Prevalence Area. The whole state will be reclassified to a Medium Prevalence Area.
Both States will also implement this change on 1st January, 2011.
Prevalence Areas in the remaining States, Tasmania, South Australia, Queensland, and the ACT, will not change at this stage.
14. Where can I obtain further information about OJD?
If you suspect sheep in your flock may be infected with OJD, contact your local veterinary practitioner.
For additional general information regarding OJD, contact your local DPI office or visit www.dpi.vic.gov.au/farming/ojd or www.ojd.com.au.
