Animal Health Australia (AHA) coordinates the national Johne’s disease (JD) in cattle Framework on behalf of the Australian beef and dairy industries, governments and veterinarians to help reduce the spread and impact of JD in Australia.
The dairy and beef industries have adopted a ‘sector’ approach to the control and management of the disease using common tools, such as sound farm biosecurity practices, testing, National Cattle Health Declarations and voluntary risk profiling tools.
What is Johne’s disease?
Johne’s disease infects most cattle as calves which often do not show any symptoms of JD for many years. They are likely to excrete the JD bacteria before developing clinical signs.
The most common signs of JD in cattle are:
- chronic diarrhoea (scouring)
- wasting
- eventual death.
Not all infected cattle show these signs; some just fail to reach their full productive potential.
First signs of JD in dairy cattle are:
- a drop in milk production
- then weight loss and—in most cases—scouring.
This would occur even though you are feeding the cattle well. Bottle jaw (soft fluid swelling under the lower jaw) can also be seen in the early stages.
First likely sign of JD in beef cattle is weight loss, with or without concurrent scouring.
How can JD enter a herd?
JD enters a herd through the introduction of infected animals, either by purchasing or agisting infected stock.
Animals usually become infected at a very early age. They pick up the infection as they eat or drink from contaminated pastures, water and udders, or drink contaminated milk from infected cows.
When pasture contamination levels are high, older animals may become infected.
Some infected animals can shed billions of bacterial organisms in their dung each day.
Approach to JD in cattle
After a 12-month consultation and evaluation of existing practices a Framework was released in February 2016 outlining the new approach to the management of the endemic disease.
The Framework clearly outlines how Australia will manage JD in cattle into the future and shifts the focus of JD management to the wider biosecurity practice of reduction and management of all diseases.
Beef sector approach
The national beef population has a very low level of JD. Co-mingling with dairy cattle or grazing on land previously grazed by dairy cattle are among the greatest risk factors for infection for a beef herd.
The Australian beef industry approach to JD promotes using tools, such as:
- Johne’s Beef Assurance Score (J-BAS) – a risk profiling tool.
- JD biosecurity checklist – help producers determine other questions they may want to ask about the JD history of the cattle and their property of origin.
- The National Cattle Health Declaration.
Biosecurity plans
J-BAS requires a property biosecurity plan for all scores. The On-farm biosecurity plan template, which incorporates the JD Biosecurity Checklist, has been developed for producers to use for this purpose (fillable form, best opened in Google Chrome or download a Word copy). This meets the national industry minimum standards of the National Farm Biosecurity Reference Manual – Grazing Livestock Production.
A range of factsheets have also been developed to assist with management of JD:
Dairy sector approach
JD is more prevalent in the dairy industry than in the beef industry.
The Australian dairy industry approach to JD focuses on:
- using the JD Dairy Score (JDDS) as an industry qualitative risk assessment
The sector also aims to minimise the risk of product contamination by promoting good calf hygiene.
Three Step Calf Rearing Plan
Because the management of calves is so important in limiting the spread of JD, the dairy industry has recommended a 3-step calf-rearing plan under previous programs.
3 steps for rearing dairy calves
- Calves to be reared as replacement heifers or bulls must be removed from their mothers and the calving area within 12 hours of birth.
- The calf rearing area, including calf paddocks, must be separated from areas used by adult cattle, and not take any drainage from laneways, yards and paddocks used by adult cattle.
- The paddocks used by calves between weaning and 12 months of age must not have had any adult cattle (older than 2 years) run on them in the previous 12 months.
The three step plan could be part of the biosecurity management plan for a dairy herd.
A range of factsheets have also been developed to assist with management of JD in dairy cattle:
Other management tools
For herds with Johne’s disease, vaccination of cattle with Silirum® should be considered. This inactivated (killed) vaccine is a tool to complement on farm disease management practices relating to JD. Producers wanting to use the vaccine in their cattle should consult with their vet, check with their relevant Department of Primary Industries (or equivalent) about any state/territory rules for using it, and also follow the label requirements for permanent identification of vaccinates.
Groups of producers may also wish to work together to enhance their biosecurity. Like-minded producers who, for example, have the same breed of cattle or who are within a particular region or supply network can use Cooperative Biosecurity Plan Guidelines that have been developed to provide a list of elements that these groups should consider when forming.
Other resources
State JD coordinators can be contacted for information about the disease and biosecurity.
Contact your local cattle veterinarian for help with testing and biosecurity plans.
Tools for vets
A useful reference document has been developed by the cattle industries, with help from the state/territory departments of primary industries. The JD in cattle Definitions and Guidelines is a resource for information on JD tests and testing, as well as other JD issues.
WA and NT entry requirements
The WA cattle industry has indicated that it wishes to maintain WA’s JD border controls to help manage the disease within that state. The Health certificate for movement of stock to Western Australia (Livestock Biosecurity Form LB1) contains all entry requirements for livestock entering WA (including JD) and is used to certify that livestock meet these requirements. It must accompany each consignment of livestock entering into WA. The full JD in cattle requirements are contained in the explanatory notes of the LB1 form.
After a recent detection of JD in cattle, WA have updated their information for producers. Find more on the DPIRD website here.
The NT cattle industry has settled on a minimum entry requirement policy of JBAS 6 from July 1 2017 (access media release here). Requirements can be found on the current NT health certificate/waybill.
For further information visit the WA and NT websites:
- Department of Primary Industries and Regional Development, WA
- Department of Primary Industry and Resources NT
From 1 July 2021 new import conditions commence for WA. Information is on the DPIRD website.
CattleMAP: has ceased
As of 1 November 2016, the Australian JD Market Assurance Program for Cattle (CattleMAP) has transitioned to alternative industry assurance systems. This outcome follows a review of CattleMAP, undertaken by Herd Health P/L on behalf of the BJD Steering Committee. The new arrangements for CattleMAP participants is the final step in the wider BJD Review process.
JD testing and diagnosis
How to diagnose JD
The diagnostic challenge of JD is detecting animals that are subclinically infected (asymptomatic carriers of the disease-causing bacteria) before they start to become infectious. This is one of the reasons that the Australian program focuses more on herd risk and herd-level assurance.
Tests for JD indicate the presence of the actual bacteria or the animal’s response to bacteria in their system.
Tests are available for JD in cattle, including tests on blood, faeces and tissues. But most tests have very poor sensitivity (ability to correctly identify infected animals) early in the onset of the disease or in young animals.
False positive results can occur in the blood test, more commonly in northern Australia due to cross-reactions with other bacteria that cattle have picked up from their environment.
Tests may be used in combination. For example, initial screening by blood test, followed by faecal culture, or a post-mortem tissue test on reactor animals.
The sensitivity of these tests increases as the disease progresses, even before signs of disease are noticeable.
Herd tests for JD in cattle
Antibody tests (serological or blood tests)
The main antibody-screening test used for JD is the absorbed ELISA (enzyme-linked immunosorbent assay) test in cattle. There is also a gel or AGID (agar gel immunodiffusion) test for goats. The blood test detects antibodies to the Johne’s disease bacteria, and results are reported relatively quickly (1–2 weeks).
Individual faecal culture test
Dung or faecal samples collected from individual animals are cultured for the bacteria. This is more expensive and slower than antibody tests (2–5 months), depending on the culture method used.
Faecal culture is used as a definitive test to confirm infection in cattle that react to the ELISA, and it can be used with antibody tests in cattle herds to increase the chance of detecting infected animals. Faecal culture is used for alpaca and deer, which have no other approved antibody tests.
Pooled faecal culture (PFC) test
Faecal samples from up to five cattle may be cultured in one pool as a herd-screening test. While the PFC test still takes 2–5 months, it is a cheaper herd test option than individual faecal cultures. If a positive pool is identified, then the individual animals need to be cultured to identify the test positive animal.
High Throughput-Johne’s polymerase chain reaction (HT-J PCR) test
Faecal samples from up to five animals may be tested in one pool as a herd-screening test. A much quicker test than the PFC with similar accuracy.
Herd environmental culture (HEC) test
The HEC test is another type of faecal test for use in dairy herds as a:
- surveillance tool in dairy herds
- test equivalent to the Check test. JD Herd Environment Culture Test Protocol (Word – 13 KB) .
Follow-up tests
Any animals or groups of animals that test positive to an antibody test are tested again with a definitive test to confirm the result. For instance, ELISA reactors are tested by individual faecal culture or by a post-mortem examination, microscopic examination of the gut tissue and possibly culture of gut tissue. These tests detect the actual bacteria or the characteristic microscopic lesions that they cause. Likewise, animals or groups of animals that test positive to the HT-J test are again tested with a definitive test, as described for serology to confirm the result.
Testing of herds
Check Test
A Check Test is either:
- 50 adult animals in the herd (or all eligible animals in a herd of less than 50 adult animals) biased to increase the probability of detecting infection, tested by pooled faecal culture, pooled faecal HT-J PCR or ELISA [not for WA entry]; or
- a HEC test in dairy herds that comply with the requirements above.
A Check Test is positive only if infection is confirmed in the herd.
Sample Test
Screening of the adult herd or a large representative sample of the adult herd by an approved test (pooled faecal culture or pooled faecal HT-J PCR, or ELISA [not for WA entry]), with follow-up faecal culture or tissue culture and histopathological investigation of any reactors (if appropriate). The cattle to be tested are selected from the herd in accordance with Appendix 2 of the JD in cattle Definitions and Guidelines document. Where a Sample Test comprises a screening test, the test is not complete until any reactors have been further investigated using a definitive test to establish the infection status of the herd (i.e. once infection is confirmed in one animal on one definitive test, it is not necessary to continue testing all reactors with definitive tests).
A Sample Test is positive only if infection is confirmed in the herd.
Table 1: Advantages and disadvantages of approved tests to diagnose JD in cattle
Test | Use | Advantages | Disadvantages |
Blood test (ELISA)—tests for disease antibodies | Screening animals older than 2 years for export or clinical cases | Rapid result
Relatively cheap Useful herd test (but not reliable as an individual animal test) |
Low sensitivity1 for individual animal tests; can fail to detect infection when it is present
Moderate sensitivity for herd tests Imperfect specificity2 results in false positive reactors, requiring further investigation (especially in northern Australia) |
Faecal culture—tests for bacteria in faeces | Confirming infection in suspect3 animals.
Herd tests. |
Highly specific
Better sensitivity than blood test Use as pooled test to reduce cost and increase throughput |
Takes 2–5 months to get a result
Relatively expensive compared to ELISA |
HT-J PCR— tests for DNA of bacteria in faeces | Screening test for animals older than 2 years | Highly specific
Better sensitivity than blood test Rapid result (one to two weeks) Use as pooled test to reduce cost and increase throughput |
Expensive compared to ELISA (similar to faecal culture)
Requires follow-up tests to confirm infection in herds not previously confirmed or suspect |
Histology—microscopic examination of tissue samples from gut | Confirming infection in suspect animals | High specificity
High sensitivity |
Requires animal slaughter and immediate collection of samples at abattoir or farm |
Tissue culture—culturing tissue samples from gut | Confirming infection in suspect animals | High specificity
High sensitivity |
Requires animal slaughter and immediate collection of samples at abattoir or farm |
1 Sensitivity is the ability to give a positive result in an infected animal.
2 Specificity is the ability to give a negative result in an animal that is not infected.
3 Suspect animals are those with clinical signs of JD or who have returned a positive blood test (ELISA).
FAQs about JD testing and diagnosis
1. How accurate are current JD tests?
To be accurate, a test must not only be good at detecting infected animals (sensitivity) but also at correctly giving non-infected animals a negative result (specificity).
The sensitivity of JD tests overall is low, (i.e. the rate of false negatives is high), especially in young or recently infected animals. Sensitivity increases as the infection progresses in the animal, so the probability of missing the infection (false negative results) decreases in older animals or in animals in the advanced stage of the disease.
Testing groups of adult animals increases the probability of detecting the infection in the herd or flock to an acceptable level.
Current JD tests have adequate sensitivity when used as a herd or flock test, but a negative test on an individual animal gives very little assurance that the animal is not infected.
The specificity of JD tests is very good, so false positive results are very rare. On average in Australia:
- AGID test (used mainly in sheep) produces about 1 false positive in 1000 tests
- ELISA (used mainly in cattle) produces about 2 false positives in 1000 tests.
One ELISA test (Parachek®) is approved for use in sheep and goats, but has a higher false positive rate (about 1 false positive per 100 tests).
There is a very small chance of a result being false positive; so all reactors to screening tests are followed-up.
The faecal tests have better sensitivity than the blood tests (ability to find diseased animals) and a very low chance of a false positive result.
2. Why aren’t animals tested when they are young?
Even though most animals become infected when they are young, the Johne’s bacterium, Mycobacterium paratuberculosis, grows very slowly.
In the early stages of the disease, the immune system is not stimulated strongly enough for it to produce detectable antibodies, so blood tests are usually negative.
Similarly, little or no shedding of bacteria in the faeces occurs early in infection, so faecal culture tests will also be negative.
So, although most animals get infected when they are young, it’s not useful to test an animal until it’s at least 2 years old when the current tests are more likely to detect the disease. (Research is being undertaken to see if the minimum age for testing can be lowered.)
The exceptions to this are deer and alpaca, where disease has progressed more quickly in cases in Australia.
Goats are tested for the GoatMAP at a minimum age of 12 months, but the check test applies to goats 2-years-old and over.
3. Why are groups of animals tested, rather than individual animals?
Sampling rates for the Market Assurance Programs (MAPs) and for surveillance programs are designed to give a high probability of detecting infection, even if a small proportion of the tested animals are infected. Finding one infected animal indicates that there is JD infection in the herd or flock, as there will almost certainly be other infected animals in the early stages of the disease that have not reacted to the test, or were not tested.
JD in cattle FAQ
If you have further questions about the management of JD, check out this FAQ page for more information.
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