Why vaccinate against ovine Johne's disease (OJD)?
Vaccination is an important tool in reducing the rates of clinical disease and deaths in an infected flock. It is also useful in reducing the level of bacterial contamination on infected properties.
Vaccination can be used to:
- reduce the level of contamination passed from ewes to their lambs
- reduce pasture contamination levels
- reduce the risk of spread between neighbouring properties
- provide lower risk replacement sheep
- aid in the protection of valuable sheep and genetics from the effects of the disease.
Producers with SheepMAP–accredited flocks may consider vaccination to provide an added measure of risk reduction.
Who should vaccinate?
Consider all OJD management options (including vaccination) carefully before choosing which best suits your individual business. Factors that need to be taken into account include:
- whether your flock is infected
- losses from OJD
- whether a neighbouring property is infected
- trading implications of OJD infection for the business
- the cost of the disease on farm compared to the cost of vaccination
- conditions of entry to shows or sales
- conditions of movement to other states
- requirements of any regular buyers of your sheep.
Vaccination to manage disease in an infected flock:
- is recommended if deaths from OJD are causing economic loss
- can decrease disease signs and deaths due to OJD
- reduces OJD bacteria in the faeces, lowers contamination of pasture and slows spread of OJD.
Vaccination of an infected flock will not eliminate the disease from the flock or property.
Vaccination to help protect against the introduction of infection
Vaccination for this purpose is generally recommended if:
- the business risk of OJD is high — for example, sellers of breeding or replacement sheep
- the likelihood of infection being introduced is high — for example, if you are in a high-prevalence area or have an infected neighbour.
Vaccination alone will not fully protect a flock from the introduction of OJD. It needs to be combined with other biosecurity measures:
- Ask for a national sheep health statement when buying sheep and only buy sheep with a high level of OJD freedom assurance.
- Maintain good boundary fences to reduce straying.
- Deal promptly with stray sheep.
If exposed to OJD bacteria, particularly high levels of bacteria, some vaccinated sheep may still become infected.
Trading vaccinated sheep
- Approved vaccinates (those vaccinated before 16 weeks of age) are required to have their National Livestock Identification System (NLIS) approved ear tag embossed with a 'V' in a circle.
- Approved vaccinate status carries additional assurance on the sheep health statement.
- Some ram export markets require a negative blood test result for OJD. Vaccinated sheep will test positive to the blood test.
Sheep will develop a swelling at the injection site which, in most cases, reduces with time. Minimise carcass damage by vaccinating high on the neck behind the ear and not vaccinating lambs destined for the abattoir. For disease control purposes it is not necessary to vaccinate animals which will be sold to slaughter by 12 months of age.
The vaccine can cause a serious reaction in humans in the event of accidental self injection. If this occurs, seek medical advice immediately.