All strains of Johne’s disease (JD) are reportable under Western Australian legislation. The presence or suspicion of JD must be reported to the Department of Primary Industries and Regional Development (DPIRD) as soon as possible.
During office hours, contact your nearest DPIRD field veterinary officer - see the Animal Biosecurity contacts webpage.
After hours, contact the exotic animal disease toll-free hotline on
What causes JD?
JD is caused by the bacteria Mycobacterium paratuberculosis.
The bacteria live and multiply in the lymph nodes and the small intestine of the animal and cause the intestinal wall to thicken. This reduces the animal’s ability to absorb food and water and results in continuing weight loss and eventually death.
Strains of JD
There are several strains of the bacteria, including sheep, cattle and bison strains. While the strains appear to have a preference for the species they are named after (sheep, cattle, bison), they are not restricted to those species – that is, any of the three strains can infect cattle, sheep, goats, alpaca and deer.
For example, sheep strain (S-strain) has the potential to infect cattle. S-strain of JD in cattle is not regulated in WA due to its prevalence in the sheep flock. For more information, see the webpage on S-strain of JD in cattle.
C-strain of JD in cattle is not known to be present in WA and is subject to a prevention program. See the DPIRD control of JD in cattle webpage for information on regulation, border controls and surveillance.
Signs of JD in cattle
JD has a long incubation period. Typically, cattle are most likely infected as calves and will not show any signs of illness until they are 3-4 years old. However, JD can cause reduced production levels and the animal can be spreading the disease even before the animal is noticeably unwell .
The visible signs of JD in cattle are:
- chronic diarrhoea that does not respond to treatment
- gradual weight loss despite normal or increased appetite with ample feed.
The signs of JD in infected animals are often triggered by stress factors such as calving, milk production and a lack of feed or poor feed. Infected animals die within a few weeks to several months after the onset of visible signs.
How is JD spread?
JD can spread among livestock through ingestion of:
- the bacteria present in the colostrum, milk and faeces of infected animals or
- soil, feed or water contaminated by the bacteria.
The bacteria can survive in the soil for up to 12 months under cool, moist conditions.
Calves are most likely to be infected by suckling udders that have been contaminated with infected faeces. They can also be infected by drinking infected colostrum or milk or grazing contaminated pasture or feed. In cattle with visible disease, calves may also be infected in-utero.
Cattle can also be infected through contact with sheep, goats, alpaca or deer infected with JD or by grazing land grazed by infected animals.
Which animals are most at risk?
Calves are most susceptible up to 30 days old and remain at risk until around 12 months old.
Cattle over 12 months old are relatively resistant and, if they do become infected, are very unlikely to develop signs of disease or shed enough bacteria in their faeces to spread the disease.
What is the economic impact of JD in cattle?
A number of export markets require JD conditions for cattle and cattle products. Where sheep or other animals are diagnosed with JD on a property, this may also affect the JD status of the property for the purposes of determining their cattle export market eligibility.
In dairy herds, JD causes economic losses through reduced milk production, reduced conception rates and restrictions on trading. In beef herds, the economic impact is still present but usually less significant.
The level of infection in a herd increases over time and, if the disease is left unmanaged, the economic effect of JD becomes increasingly significant.
How is JD in cattle managed in Australia?
Under the national framework implemented in 2016, if JD is diagnosed, it must be reported to state or territory agricultural authorities, but disease control is not prescribed at a national level. C-strain of JD in cattle is regulated in WA as prior to the new national framework, WA was considered free of bovine (C-strain) JD. See the webpage Control of JD in cattle in WA for more information.
Under the national framework, producers can manage the risk of JD occurring on their property by using biosecurity tools such as the market assurance schemes Johne’s Beef Assurance Score (J-BAS) and Dairy Score and implementing farm biosecurity plans.
More information on the new approach to JD in cattle and biosecurity tools to manage the risk of JD can be found on the AHA website. The Department website also has a J-BAS factsheet and flowchart tailored for WA producers.
How do we test for JD?
Several tests are available for JD, but all should be applied with recognition of their limitations.
- blood tests – which look for an immune response to infection
- faecal tests – looking for bacteria in the faeces by culture or finding bacterial DNA (polymerase chain reaction testing)
- post-mortem tests – looking for bacteria in the gut and lymph nodes under a microscope,
Blood testing is not very specific and is likely to give some false positives (give a positive result even if there is no disease agent). It is a useful screening tool, but is not used for definitive diagnosis.
Testing faeces is not very sensitive when applied at an individual animal level as it will only detect infection in animals shedding bacteria. It is better used as a herd test rather than on individual animals. Young animals that have not commenced shedding will test negative even if they are infected.
Looking at gut and lymph nodes under the microscope and finding the bacteria in faeces and tissue samples are the most sensitive methods for detecting the disease in an individual animal, but will not pick up all infections, especially in young animals. It takes more than three months to obtain results from culture of tissues or faeces.
If a positive test is received, further testing by histology or culture is carried out to confirm the diagnosis.
For details of testing and sampling requirements, refer to Animal Health Australia’s (AHA) website.