Control Options for Bovine Johne’s Disease in Dairy Herds
Note Number: AG0933
Published:November 2001
Updated: November 2010
Bovine Johne's disease (bjd) can be present in a herd for years before signs of the disease emerge. For this reason, all dairy farmers should manage their farms as if their herds are infected.
The Department of Primary Industries (DPI) facilitates the provision of Johne’s disease control and management advice to the owners of dairy herds infected with bjd. DPI’s Biosecurity Victoria Animal Health staff liaise closely with private veterinarians who work with herd owners and managers to provide disease control and management advice and develop a bjd control program tailored to the property.
Recently purchased/introduced infected animal
If an infected animal has been recently introduced into the herd, there is a possibility that the main herd is not as yet infected. Options in this scenario include:
- Cull the infected animal along with all adult animals from the same source as soon as possible.
- Cull all calves that may have been exposed to manure from the source herd. These calves are not likely to shed bjd bacteria until they are 2 years old. They should be sold for slaughter prior to this age.
- Restrict access of calves to any land contaminated with manure from the cattle from the source herd, for at least 12 months.
Infected cattle bred on the property
If the infected animal was bred on the farm, it must be assumed that bjd is established in the herd. To effectively control bjd in dairy herds, owners must endeavour to:
1. Prevent bjd spread within the herd
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Fig 1. Remove calves from their dams |
Sound calf rearing is the key to stopping bjd spread within the herd. To prevent this spread, you must:
- Calve cows in clean, well-drained paddocks; avoid heavy manure contamination.
- Remove calves from their mothers within 12 hours of birth; use a clean trailer to move calves from the calving paddock to the rearing area.
- Double-fence calf-rearing areas from cow laneways and tanker tracks.
- Ensure calf-rearing areas are not contaminated by dairy effluent, or drainage from paddocks in which adult cattle are run.
- Ensure calves under 12 months only graze paddocks that have been free of adult cattle for at least 12 months.
- Ensure boots, clothing and farm machinery including the tyres of motor bikes and calf transport trailers are free of manure before entering calf-rearing areas.
- Consider feeding calves with milk-replacer because milk from infected cows can pass on bjd to calves. Feeding whole milk is very risky in heavily infected herds; If whole milk has to be used ensure that it has been collected from low risk animals such as cows which have been tested blood tested negative and are from family lines which don’t have a history of bjd.
- Provide calves under 12 months with clean tank, town or bore water; avoid water from dams, channels and creeks that might be contaminated by manure.
The Johne’s Disease Calf Accreditation Program (JDCAP) and the Dairy Australia endorsed 3-Step Calf Program employs many of the above principles. The JDCAP program is mandatory for entry into the Test and Control Program (refer to Agnote 1202 – TCP3). However, JDCAP is available to owners of any dairy herd irrespective of the bjd status.
2. Isolate and cull cattle showing signs of bjd
Cattle showing signs of bjd shed enormous numbers of bacteria in their manure, contaminating pasture. Scouring and wasting animals must be strictly isolated from calves and investigated promptly by your veterinarian. Bjd clinical cattle must be disposed to a knackery or on farm. Cattle showing clinical signs of bjd must not be dispatched to a saleyard or abattoir.
3. Identify and cull high-risk cattle
Culling high-risk cattle speeds up the progress of bjd control and may one day lead to eradication of bjd from the herd.
It is important to identify and cull cattle that might be bjd carriers. These high-risk cattle may show no signs of bjd, but can be shedding the bacteria in their manure. High-risk cattle should be culled for slaughter as soon as possible.
To identify and cull high-risk cattle, it is vital that all cattle are permanently identified and accurate records kept of each animal's origin, birth date and parentage.
High-risk cattle for culling include:
- The dam (mother) and any progeny of a clinically affected cow and also maternal sisters and brothers.
- Cattle that test positive (reactors) to a blood test (in a known infected herd , these reactors are deemed infected)
- The dam and any progeny of blood test positive cattle.
- Cattle that were exposed, as calves, to manure of an animal breaking down with bjd (eg. grazed the same paddock).
- Any other cattle that may have been exposed to the bacteria as calves: eg. reared in the same year as a confirmed case, or purchased from the same source.
Keep bjd out of the herd
If you have gone to the effort and expense of bringing bjd under control, it makes little sense to allow the problem back in. To minimise the risk of re-introducing bjd, owners should:
- Secure boundary fences and gates to keep out stray cattle.
- Run a self-replacing herd, or
- Purchase cattle only from owners who:
- practise safe calf-rearing, as per the Johne’s Disease Calf Accreditation Program (JDCAP).
- can demonstrate through herd testing and management that their sale cattle are low-risk.
- will provide a signed Vendor Declaration or the National Dairy bjd Assurance Score Declaration form (available from www.dpi.vic.gov.au/farming/bjd), stating a low-risk BJD status
- Avoid introducing bjd through agistment (as above ask for a signed Vendor declaration or Health certificate, stating low-risk bjd status); do not allow contact of calves less than 12 months of age with adult cattle, regardless of their origin.
- Beware of deer, goats and camelids (alpacas, llamas); these species can be infected with bjd Do not allow them to contaminate paddocks grazed by cattle less than 12 months of age.
Never introduce cattle from herds of unknown bjd status, particularly if their calf rearing practices are unsound.
Further information
Further information about bjd can be obtained from your private veterinarian, DPI Animal Health staff or refer to the DPI web site: http://www.dpi.vic.gov.au/farming/bjd.
Acknowledgements
The Agriculture Note was originally developed by Alan Ross, Animal Health Field Services, in December 2005. This November 2010 version was reviewed by Dr David Champness, Biosecurity Victoria.
