Johne's disease in WA
Following the detection of Johne’s disease (JD) cattle strain (C-strain) in cattle in WA, the Department of Primary Industries and Regional Development (DPIRD) and WA industry agreed it was not technically feasible or economical to eradicate JD.
Please refer to the webpage: Forms for importing livestock into WA for further information on the import conditions.
For more information on JD in cattle regulation, please see the webpage: Changes to regulatory controls for JD in cattle in WA.
The video presentation: Johne's disease management in WA provides an overview of the disease and information on biosecurity planning.
What is Johne’s disease?
Johne’s disease (JD) is a chronic incurable infectious disease that affects cattle, buffalo, sheep, goats, alpaca and deer. It is caused by the bacteria Mycobacterium avium subsp. paratuberculosis and results in progressive diarrhoea, weight loss, reduced production and eventually death. The signs of JD in infected animals are often triggered by stress factors.
JD is JD, whatever the species or the strain
JD is defined nationally and internationally as infection with any strain of Mycobacterium avium subsp. paratuberculosis, which includes sheep (S-strain), cattle (C-strain) and bison (B-strain). These strains can affect more than one species, not just the strain they are named for. JD in cattle is commonly referred to as bovine JD (BJD) and in sheep as ovine JD (OJD).
How are cattle infected with JD?
JD can be spread between livestock through:
- faeces of infected animals or infected or contaminated colostrum or milk
- soil, feed or water contaminated by the bacteria. The bacteria can survive in the environment for long periods, including in soil for up to 12 months.
Young animals, under 12 months, are most susceptible to becoming infected, usually through suckling udders contaminated with infected faeces. They can also be infected by drinking infected or contaminated colostrum or milk and grazing contaminated pasture or feed. In pregnant livestock with visible disease, animals may rarely be infected in utero (prior to birth).
Any susceptible livestock can be infected through contact with faecal contamination from another susceptible species, whether cattle, sheep, goats, alpaca, deer or buffalo, or by grazing land grazed by other infected livestock.
While animals are usually infected early in life, they do not shed the bacteria for a number of years nor do they show signs of disease until they are much older. They are not infective (capable of spreading the disease) to other animals until they start to shed the bacteria in their faeces, usually after 3–5 years of age. This is important in managing the disease on a property.
Testing for JD
Several tests are available for JD, but they all have limitations, as detailed below. These limitations should be considered when undertaking any testing.
Testing large numbers of homebred animals over four years old provides the best chance of detecting the disease. The larger the number of animals tested with negative results, the more confidence you can have in the results indicating a low likelihood of infection on that property and animals originating from that population.
Producers should consult their veterinarian to determine the most appropriate testing for their property. A veterinarian can also advise on the suitability of testing undertaken on properties where livestock may be sourced.
Available tests for JD are:
- Faecal tests – Faecal testing is best used for herd-level testing. The tests look for bacteria in the faeces (by culture) or bacterial DNA (by using polymerase chain reaction (PCR) tests. Faecal tests are not very sensitive when used for individual animals as they will only detect infection in animals shedding bacteria, which can occur intermittently. Faecal testing will not detect infection in young animals that are not shedding yet.
- Blood tests – These look for an immune response to infection. There are known cross reactions to this test with other Mycobacterium bacteria that can lead to a false positive result. Blood tests are less sensitive than PCR tests and only detect an immune response after infection is established, which is unlikely before four years of age. Blood tests are not used for definitive diagnosis.
- Post-mortem and laboratory testing – These involve examining dead animals to look for gross and microscopic changes indicative of JD infection and detecting bacteria in the gastrointestinal tract and lymph nodes. Pathological changes may be detectable before clinical signs are seen in an animal.
Biosecurity planning for JD
As it may be several years between the time of infection and livestock being capable of spreading the disease or showing signs of disease, there are three key factors WA producers should consider when undertaking JD biosecurity planning. These are the impact of JD at an individual property level, the likelihood that JD will be introduced onto the property, and property-level risk mitigation strategies.
Impact of JD on the individual property
The level of risk mitigation necessary will depend on the individual property’s business model. Producers should consider:
- What would the production impact be if JD is introduced onto the property?
- How would property management reduce or worsen the impact of the disease?
- What are the live export market access requirements in relation to JD?
- What are the potential requirements of domestic clients? (These may vary for studs compared with properties supplying livestock for abattoir processing.)
Likelihood that JD will be introduced onto the property
The most common way JD enters a property is when infected livestock are brought onto property.
When assessing the likelihood that JD could enter the property via introduced livestock, producers should consider the source of any introduced susceptible livestock, for both interstate and within WA introductions, and the supplying property status using:
- risk-profiling tools, such as Johne's Beef Assurance Score (JBAS), Johne's Disease Dairy Score (JDDS)
- National Health Declarations
- biosecurity plans and biosecurity checklists
- testing history
- vaccination status and
- history of movement of susceptible livestock species onto that property.
Property-level risk mitigation strategies
When developing property-level risk mitigation strategies, producers should consider:
- risk-profiling tools (such as JBAS, JDDS)
- biosecurity plans and biosecurity checklists
- National Health Declarations
- grazing management, including not co-grazing with other susceptible species and not grazing on land previously grazed by unknown status or infected livestock
- herd-level faecal testing
- vaccination and
- calf-rearing programs as relevant to the property/enterprise.
Developing and maintaining a farm biosecurity plan will help you to identify and manage risks to your business from JD. The plan should include decisions on but not limited to herd introductions of all JD-susceptible species, co-grazing with JD-susceptible species, testing and vaccination.
Consider origin and history of cattle/sheep to be introduced
Livestock such as cattle, sheep, goats and alpacas can be infected without showing any signs of disease and producers should consider the livestock origin and the history of the source property before introducing livestock to their property. Sourcing animals from properties with a negative testing history for JD and which run closed herds or have no or minimal low-risk introductions can help to reduce JD risk. Properties which have sourced susceptible livestock from properties with no testing history or from an area in Australia with a high prevalence of JD are at a higher likelihood of disease.
Ask for a health declaration
Producers are encouraged to ask for a National Health Declaration when purchasing livestock. The declaration shows the livestock’s biosecurity and health information including the test and clinical history of the supplying property and the livestock’s vaccination status. The National Cattle and Sheep Health Declarations include vaccination status of the individual animal. Vaccination can reduce the likelihood of this animal shedding disease if applied in accordance with manufacturer’s directions, even if the herd status of the source property is unknown.
Ask for industry assurance program/tool scores
The Johne’s Beef Assurance Score (PDF download), Johne’s Disease Dairy Score and Market Assurance Programs for sheep, goats and alpacas are voluntary risk-profiling tools for their respective industries. Properties with a higher score are considered less likely to have JD, however, the scores are a guide only and should be used in conjunction with other biosecurity practices to minimise the risk of introducing JD onto your property.
JD testing on properties
Testing on properties you are considering buying from
Understanding the history of laboratory testing for JD on a property is an important part of profiling the likelihood of JD being present on the property. Although infection generally occurs in the first 12 months of life, JD has a long incubation period and can only be detected by laboratory testing once the animal is shedding the bacteria, which usually occurs after 3–5 years of age.
Individual animals may also shed the bacteria intermittently and produce a false negative result, even though they are infected. This means faecal testing for JD should be undertaken on a representative herd level, involving testing large numbers of homebred livestock over four years of age, rather than an individual animal level. A property with negative herd-level laboratory tests repeated over a number of years has a higher confidence of freedom from the disease.
Testing on your property
Testing for JD is an important strategy that producers should also consider on their own property. Because livestock may be shedding the disease intermittently, meaning they could test negative but still be infecting other animals on the property, regular and repeated herd-level faecal testing is important to detect the disease early before it spreads within the property.
Subsidised testing and benefits of early detection
The consequence of having or introducing animals with JD to your property can be reduced by early detection through regular JD herd level testing of homebred livestock over four years and veterinary investigations of scouring or ill-thrifty livestock. Producers who suspect they have livestock with JD may be eligible for a subsidised veterinary investigation and testing through the Significant Disease Investigation (SDI) program.
Potential market impacts
Note that detection of JD in any species on a property can mean the property is ineligible to supply livestock for some live export markets. See the Trade and market access section for more details. There may also be an impact on Johne’s Beef Assurance Score and Johne’s Disease Dairy Score status.
Preventative biosecurity and property management
Good biosecurity is fundamental to preventing introduction of all pests and diseases, not just JD. This includes:
- maintaining secure boundary fencing
- preventing access to drainage channels and waterways
- using water troughs
- ensuring all visitors clean their boots, vehicles and equipment before entering the property.
Young stock are most susceptible to infection and should be protected from potential sources of infection such as waterways from neighbouring properties or contact with older, potentially shedding animals.
Intensively grazed animals in high-rainfall areas are most at risk of contracting and spreading JD due to their stocking density and increased exposure to potentially contaminated faecal material and the survivability of the bacteria in that environment.
Livestock should not be co-grazed with other susceptible livestock species as JD can be spread from one species to another.
Producers should also avoid grazing cattle on land previously grazed by sheep and/or vaccinating sheep to minimise the JD risk to cattle, given that JD is endemic in sheep in WA.
Producers should consider regular testing for JD to give the best chance of early detection should the disease occur. See: JD testing on properties.
Obligations to report suspicion or detection of JD in livestock
Under the Biosecurity and Agriculture Management Act 2007 (BAM Act), the detection of any strain of JD in any species in WA must continue to be reported, in order to support certification for live export markets. As a reportable disease, anyone with a suspicion or detection of JD in livestock must report it to a BAM Act authorised inspector, such as a DPIRD Field Veterinary Officer, as soon as possible.
DPIRD’s management of JD (C-strain) detections will align with the national decision to deregulate JD in cattle in 2016 and with the current management of detections of S-strain in cattle and any strain of JD in sheep in WA.
It is recommended producers manage the spread of JD within their property. Management practices to reduce spread on affected properties include culling affected animals and exposed offspring, not providing raw milk to young stock and considering vaccination strategies appropriate to your enterprise.
Vaccination of cattle with Silirum
Silirum is not currently approved for use by veterinarians in cattle in WA. DPIRD will notify cattle industry stakeholders when the legislative requirements for supply of the vaccine are finalised. Veterinarians whose clients have indicated an intent to undertake vaccination are encouraged to email DPIRD at email@example.com and provide the name of the veterinary practice, contact name and details (phone number, email address and physical address) and the approximate number of producers wishing to take up vaccination.
Silirum is an inactivated (killed) vaccine that may not prevent infection with JD, but can significantly reduce its spread by reducing shedding of the bacteria in infected cattle. Vaccination is most effective when given to calves between three and six weeks of age, however vaccination of cattle older than this may reduce shedding.
Producers may consider vaccinating cattle with Silirum, particularly when introducing cattle, or in herds where JD has been confirmed. Vaccination should be used to complement on-farm disease management practices and as a part of a general farm biosecurity plan to minimise the likelihood and impact of JD.
Cattle studs, including those not known to be infected with JD, may wish to vaccinate their sale calves to give buyers increased assurance that the cattle will not spread JD later in life if the property is subsequently found to be infected.
It is important to be aware that vaccinated cattle may be ineligible for export to importing countries with JD or tuberculosis requirements. The vaccine can cause (false) positive results for both JD (when undertaking blood testing) and tuberculosis (caudal fold test).
It is an Australian Pesticides and Veterinary Medicines Authority (APVMA) labelled and legislative requirement that all animals vaccinated with Silirum must be identified as Silirum-vaccinated by applying a three-hole punch, preferably in the outer third of the right ear. The person giving the vaccine must ensure vaccinated animals are recorded in the National Livestock Identification System (NLIS) database as JD vaccinated.
The Silirum vaccine should be applied in accordance with the label instructions to reduce the likelihood of carcass damage and ensure occupational health and safety requirements are met.
Trade and market access
Impact of JD detection on eligibility for live animal export markets
Live animal export market access requires Federal Department of Agriculture, Water and the Environment (DAWE) and DPIRD verification that both the individual animals being exported and the supplying property of origin meet the importing country’s requirements.
DPIRD’s property of origin statement verification, which underpins the DAWE international certification, verifies that the WA supplying property meets the requirements.
Requirements for JD (all strains) vary between different countries and producers should contact DAWE or view the Manual of Importing Country Requirements for specific market requirements. Market requirements may change over time, so it is recommended to confirm requirements with DAWE in advance of preparing livestock.
The detection of JD, irrespective of strain type, would make the property ineligible for some live export markets for the timeframe defined in the importing country requirements. Detection of JD in either your cattle or your sheep may mean you are ineligible for the defined timeframe to supply either or both species to markets with JD import requirements. Please contact DPIRD at firstname.lastname@example.org if you have any queries whether your property meets any market-specific eligibility requirements.
Impact of vaccination with Silirum on eligibility for live animal export markets
Eligibility for live animal access to international markets may be affected by vaccinating cattle.
Cattle intended for live export to countries requiring tuberculosis (caudal fold) testing must not be vaccinated with Silirum. Cattle given the Silirum vaccine are likely to test positive for tuberculosis due to cross-reactivity between the vaccine and the test. Similarly, cattle intended for live export to markets with either JD blood testing requirements and/or certification of JD freedom property status should not be vaccinated with Silirum as they may test positive if tested for JD using an ELISA blood test. Note that properties with both vaccinated and unvaccinated cattle may supply unvaccinated cattle for markets with JD or tuberculosis requirements.
All animals vaccinated with Silirum must be correctly identified as Silirum-vaccinated and recorded in the NLIS database as JD vaccinated – see details under the heading: Vaccination of cattle with Silirum.
More information and resources
Biosecurity and management tools
The national Johne’s disease (JD) in cattle guidelines have been developed for the Australian beef and dairy industries and veterinarians to help reduce the spread and impact of JD in Australia.
The Australian beef industry approach to JD promotes using tools, such as the:
Animal Health Australia (AHA) has developed a range of factsheets to assist with management of JD in beef cattle:
- Understanding Johne’s disease in beef herds
- Avoiding JD in beef herds
- Managing an infected beef herd
- Testing for JD in beef herds
The Australian dairy industry approach to JD focuses on using the risk-profiling tool Johne’s disease dairy score (JDDS).
AHA has developed a range of factsheets to assist with management of JD in dairy cattle:
- Understanding JD in Australia dairy cattle
- Avoiding JD in dairy herds
- Managing JD in a dairy herd
- Testing for JD in dairy cattle
More information can be found at AHA's:JD frequently asked questions.