6.04 - Infectious disease risk assessment protocols.

Disease

Risk assessment

Bovine Johne’s disease (BJD)

• Purchase cattle from low-risk (Free and Protected) zones, maps for these areas are available from state departments of agriculture and Animal Health Australia. In Control and Residual zones, BJD is common in dairy herds but uncommon in beef herds that have had little or no contact with dairy cattle.
• Observe regulations with regards to the movement of cattle between BJD zones and states.
• Source replacement animals from Market Assurance Program (MAP)assessed herds.
• Do a Check Test. 
  • A Check Test requires 50 adults to be tested, or all adults over two years if there are less than 50 in the herd, and is valid for 12 months. 
  • They can only be used to support a Vendor Declaration of animals bred in that herd or for animals introduced with a vendor declaration as originating from Check Tested or higher status herd. 
  • In non-MAP herds with no suspicion of infection, it is possible to undertake a low level assurance test on selected adult animals in the herd aimed at increasing the probability of detecting infection.
  • Additional testing procedures including Testing to MAP Standard (TMS) and Tested 4 year olds (T4YO) are sometimes used for cattle to gain entry to MAP MN1 herds.
• Bring in Beef Only animals. Beef Only is a herd category to help assure cattle buyers about the very low risk of BJD in beef herds that have had no contact with dairy cattle. Find out more about the requirements and declarations needed for buying and selling Beef Only animals.
• Only introduce cattle to property if they are at a similar or higher status. On-property quarantine is not practical for controlling BJD given the long time delay for development of disease and low sensitivity of tests in individual cattle. 

Mucosal disease (bovine pestivirus or BVDV - bovine viral diarrhoea virus)

• For property that is sero-negative, only buy from sero-negative herds or cattle that have been tested negative PI (persistently infected). 
• If buying only sero-negative or negative PI animals is not practical consider vaccination (check the cost benefit) or exposure of breeding animals well before joining to a known virus shedding PI animal.
• Purchase cattle from property with no history of trading, agistment or cattle turnover. 
• Purchase of cattle from closed herds presents a lower risk but this is not a guarantee of freedom from pestivirus. It is important to remember that 90% of herds in Australia have some evidence of infection.
• Introducing any cattle to a closed breeding herd is high risk where the breeding herd may be naïve (haven’t been exposed to virus).
• Do not introduce new cattle to a breeding herd in the early stages of pregnancy - this is a high risk action.
• If purchasing new cattle, keep them in isolation, and away from direct contact with breeding cows if they are pregnant (especially before 150–180 days gestation).