Since Autumn has arrived if you haven’t completed your annual Johne’s Disease (JD) testing you are missing out on an important part of your annual herd health routine. JD testing helps assess the likelihood of infection and provides crucial animal-level results. There are two different tests used in cattle within the Irish Johne’s Control Programme (IJCP). The first is the ELISA test which looks for the presence of antibodies (the animal’s immune system response to the presence of infection) in the blood or milk sample. Secondly, we have the Ancillary PCR test (ANC) which looks for the presence of DNA from the causative bacteria Mycobacterium avium subspecies paratuberculosis (MAP) in a faecal sample. JD testing helps assess the likelihood of herd infection and provides crucial animal-level results. These results support informed decisions, allowing the culling and management of high-risk animals (test positive), identification of high-risk groups within the herd and informed breeding policies which reduce risk to the next generation. Completion of JD testing allows a Veterinary Surgeon to provide targeted advice, focused on your individual herd health circumstances.
Johne’s Disease (JD) Testing in 2025 – get it organized before it’s too late!
By: Liam Doyle
Johne's Disease Programme Manager
ELISA milk/blood herd testing
- Timing Between Tests
There must be at least six months (180 days) between the start of one Johne’s testing round and the next. - Using Milk Recording
If your farm uses milk recording, it can be a cost-effective and labour-saving way to complete most of your Johne’s testing.- Organise this through your Milk Recording Organisation (MRO).
- Best practice: test during mid-lactation (May to September).
- Avoid TB Testing Overlap
Johne’s testing can’t be carried out within 90 days of the first injection of a TB test.- If your herd is undergoing frequent TB testing, speak to your vet. In certain cases, testing may be allowed from 60 days.
- When to Avoid Milk Samples
- Don’t collect milk samples within 7 days of calving.
- Avoid the late stages of lactation.
Both scenarios can result in higher rates of false positives, making it harder to identify high-risk animals.
- Eligible Cattle
All cattle over two years old must be tested – Remember to test bulls as they have exposure to the whole herd and are thus a high risk when it comes to disease spread. - ICBF Johne’s Webpage Tools
The ICBF Johne’s site https://icbf.com allows you to:- Generate a list of all eligible animals for testing on a selected date.
- See which animals were missed and need to be included in a sweeper test.
- Identify animals requiring additional faecal testing.
Ancillary PCR Faecal Test (ANC)
One of the advantages of a herd being part of the IJCP is the funding of the ancillary PCR faecal testing (ANC) in herds with positive blood/milk ELISA results and which have never disclosed Johne’s disease previously. The ANC test serves two main purposes:
- Confirming the Presence of MAP in the Herd
A positive ANC result confirms that MAP – and therefore JD – is present on the farm. Once MAP infection is confirmed, any animals testing positive or inconclusive on ELISA are likely infected.
- Clarifying ELISA-Positive Results in Previously Uninfected Herds
When an animal tests positive on ELISA:
- A positive ANC confirms the animal and herd are infected with MAP.
- A negative ANC means no MAP DNA was found in the faecal sample. This is encouraging but doesn’t rule out infection. The disease may still be in its early stages, with antibodies present but not yet shedding DNA. These animals are classified as “suspect” and pose a possible infection risk.
Currently AHI are messaging IJCP members who have outstanding 2025 ANC tests to contact their Veterinary Surgeon and get testing organized. Completion of this is an important part of the programme and is fully funded in eligible herds (herds which have not previously disclosed JD
AHI Stakeholders
AHI gratefully acknowledges the financial and other contributions of our stakeholders.
