What is Johne's?

Johne's disease is a chronic, progressive intestinal disease caused by infection with Mycobacterium avium subspecies paratuberculosis (Map). For Johnes Control Fact Sheet click here.

The disease has a long subclinical phase, during which animals can spread the infection without themselves exhibiting signs of illness. Infection causes abnormal thickening of the lining of the intestinal tract in infected animals restricting the absorption of nutrients. Clinical signs of animals infected with Johne's are long lasting diarrhoea and extreme weight loss despite the animal having a good appetite (cattle over 18 months).

Animals are usually infected when young with calves being 80% more susceptible in their first month of life. The calf may be infected while in the womb, by drinking infected colostrum and milk, or by ingesting faeces. The organism may last for a year in slurry or on pastures. An infected cow can shed billions of organisms into the environment for years prior to showing any clinical signs of the disease. Only 1-5% of infected cows in a herd will show clinical signs of the disease. The rest of the infected animals will appear healthy, highlighting the need for testing. Infection is almost always introduced to a herd by purchasing infected replacement breeding stock including bulls.

Testing is carried out using a milk or blood ELISA to test for antibodies. Single antibody tests are unreliable for confirming infection but can merely give an indication as to an animal’s status. This combined with the sporadic nature of the animal’s antibody response makes it a challenging disease to detect and respond to. NML recommends repeat testing of animals to confirm status before management decisions are made.

To view a video on Johne's made by the FUW please click here.

NML Testing Services

NML offers Johne’s antibody testing for beef and dairy herds using blood or milk samples.  For additional information please refer to the Johne’s User Guide. To order a copy, please phone 0844 7255567.

Herd-Level testing

NML recommends a 30-cow milk screen to detect herd level infection in dairy herds (blood screens can be performed for beef herds).  This should be targeted at the animals most likely to show a positive result. Cows should be between 3 and 7 years old and should be selected according to their condition, whether they have problems with lameness, high SCC or mastitis or whether they are depressed poor performing individuals.  Bulk milk Johne’s tests are not recommended due to the false confidence that can be placed on ‘low’ results.  A relatively high percentage of animals could be shedding antibodies into the bulk milk tank before the test would return a ‘medium’ result.

30-cow screen   -  £75

Cow-Level testing

NML offers a number of flexible testing to fit with any farm.  Ad hoc testing can be performed on blood or milk samples for any customer.  For dairy farmers, NML offers the CHeCS approved Herdwise Scheme, which is available to all NMR-recorded herds.  It involves testing milk recording samples for Johne’s antibodies on a quarterly basis.  Each cow generates her own result profile over the year and she will be classified into a risk group (J0 to J5) according to the risk of transmission of Johne’s to the herd.  The traffic light system; green (J0 – J2), amber (J3, J4) and red (J5) is applied to each risk group allowing vets and farmers to make educated decisions on the management of those respective groups.  Results are reported in three separate reports; a high risk report, low risk report and summary report (shown below).  For more information please consult our Johne’s user guide.


To order Individual milk tests for Johne's simply ask your NMR milk sampler to fill out a blue form to be included in with you recording samples. For Non NMR herds please call customer services to request sampling pots on 042 96 75 353 or email

To order a blood test just ask your vet to take a blood sample and submit it to the NML laboratories.



Results are available through normal notification methods. These include post, fax, email or online via the milk quality monitor on Herd Companion.


For ad hoc SCC or constituent testing contact IML