Ovine Johnes disease
Ovine Johnes disease (OJD) is most prevalent in high rainfall areas such as south eastern NSW (eg Yass, Wagga) and Victoria (excluding the Mallee).
Cases of OJD have recently been diagnosed in areas where we typically haven’t seen it before, so it is important to be on the lookout for signs of OJD in your flock.
What is ovine Johnes disease (OJD)?
OJD is a chronic wasting disease of sheep. It is caused by infection with the bacteria Mycobacterium avium subsp. paratuberculosis. Infection causes thickening of the intestines stopping the absorption of nutrients. This leads to loss of condition even when the sheep is on good feed. If on poor feed or stressed the disease may be noticed sooner.
The disease is spread when a susceptible sheep eats or drinks something which has been contaminated by infected faeces. OJD has a long incubation period and there is no treatment or cure.
The focus is, therefore, on preventing clinical cases within a flock or stopping infection from entering a flock in the first place.
Clinically affected sheep will waste away until they die or are euthanased. Scouring can sometimes be seen but is not a common symptom.
Due to the long incubation period, the disease is not usually seen in sheep until they are over 2 years old.
OJD can present as a distinct ‘tail’ to the mob which will not improve by placing on better feed or with treatment with drenching or antibiotics.
Often skinny sheep are first noticed when the flock is brought in for shearing or during lambing.
More information can be found here Skinny sheep? It could be ovine Johne's disease
Protecting your flock against OJD
The main way of introducing disease onto your property is buying in infected sheep, such as rams or replacement ewes. However, infection can also come in with infected stray sheep or by infected faeces moving down slopes or in water courses.
You can use your farm biosecurity plan to outline what preventative practices will best suit your farm. OJD is usually more of a concern for people with self-replacing flocks, rather than those who buy in and fatten for the prime lamb market, as lambs are sold before clinical OJD can develop.
To try and keep out infection you can purchase sheep that are low risk of carrying disease. This can be done by getting a Sheep Health Declaration before purchasing sheep.
Gudair® vaccine is available to help prevent deaths and reduce the amount of bacterial shedding from OJD infected animals. However as the vaccine does not completely eliminate the shedding of the bacteria, it is possible that buying vaccinated sheep from an infected farm could still lead to the introduction of the disease.
Besides being used to help protect your flock against disease vaccination can also be used as a marketing tool, especially if selling sheep into areas where OJD is a widespread issue. Vaccination involves giving one injection to lambs less than 16 weeks old. These animals are then called approved vaccinates and can be identified with a V in a circle on their National Livestock Identification System (NLIS) eartag.
Safety is very important when using the vaccine to prevent accidental self-injection or a reaction in the sheep. Good restraint of sheep, vaccination technique and use of a safety applicator (ie Sekurus) help to reduce the risks.
Read safety data sheet before use.
Most farmers choose not to vaccinate wether lambs or lambs destined for the fat lamb market as they will be slaughtered before the animals could shed disease. If you are considering holding onto wethers for a longer period, for example if the wool price goes up, it may be worthwhile vaccinating them as well.
Gudair® is a killed vaccine, it is impossible to introduce OJD onto a property by starting a vaccination program.
More information on preventative approaches:
An overview of the vaccine:
Safety information about the vaccine:
Video on how to use vaccine:
What should I do if I think I have OJD?
If you have an issue with skinny sheep call your local district vet to investigate the problem.
We can examine sheep and do testing at no cost to producers to see if OJD is present in a flock.
What happens if you are diagnosed with OJD?
While OJD is a notifiable disease in NSW, it does not result in any movement restrictions being placed on the property.
Within NSW there are no restrictions selling from an OJD infected flock. There is a general biosecurity duty to try and limit the spread of diseases, which means doing what is reasonable and practical to help prevent the spread of disease. This could be done by starting a vaccination program, filling out a National Sheep Health Declaration when selling store sheep, or sending unvaccinated stock directly to abattoir, etc.
For the other states it is best to check with the relevant state authority.
A brief summary of the restrictions/requirements for sending sheep from an OJD infected property:
Restrictions or Requirements
No restrictions on entry
Need a Health Certificate.
Have to tell the purchaser about OJD.
Since July 2019 no movement restrictions. Gudair vaccine recommended. Need a National Sheep Health Declaration
Discharge your general biosecurity obligation
No suspected or confirmed Johnes Disease in livestock in the last 5 years
Sheep aren’t allowed due to bluetongue risk – except Damara’s if you have a permit from the chief inspector of livestock
There may be some countries that do not allow the live export of sheep from OJD infected properties.
If I do have OJD how can I manage it?
If you are diagnosed a District Vet will talk you through all the options available.
As a general rule, you have the choice of managing the disease or eradication.
Most producers choose to manage the disease. This is usually done by using Gudair® vaccine on the lambs and limiting contamination of pasture with bacteria using grazing management and culling of clinically affected animals.
For further information:
Contact our District Vets:
- Mark Corrigan email@example.com 0428 256 431
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