The Assurance Based Credit (ABC) Scheme for OJD was introduced in July 2004. The ABC Scheme is used when trading sheep in Australia. Sheep to be moved or sold will be covered by a National Sheep Health Statement that will include the ABC score - the higher the score the more assurance you will have to protect your Ovine Johne's Disease status. The National Sheep Health Statement will assist producers clearly identify the animal health status of sheep offered for sale.
Well it's more like 0 to 10...and there's some adding up involved. Under the ABC Scheme, a sheep producer can claim credit points for his or her sheep under four categories. These are:
CATEGORY A. Area and flock of Origin - The known Johne's disease status of the flock or area in which the flock is located.
CATEGORY B. OJD testing history, including flock tests for the SheepMAP, as well as Abattoir 200 and Abattoir 700 testing
CATEGORY C. Vaccination history
CATEGORY D. Risk Assessment of consignment sheep
The numbers of credits assigned under each category is based on scientific risk assessment. A consignment of sheep can have up to 10 credits in total. Each additional credit represents an approximate four-fold decrease in the risk that the sheep are infected. So sheep in a consignment with a score of 4 are about 64 times less likely to be infected than in a similar consignment of sheep with a score of 1 (that is, the difference of 3 credits means a difference in risk of 4 x 4 x 4 = 64).
So, by buying sheep with a high ABC score you can greatly reduce the risk that you will buy in OJD.