Recent research into Johne’s disease

Johne’s disease remains a major challenge for the dairy industry, and recent research is helping us better understand how it spreads and how herds can be protected. This page summarises key findings from AHDB-funded studies to support vets and farmers in managing the disease effectively.

Reputation was voted the highest priority by levy payers in the 2022 Shape the Future vote, scoring 4.5 out of 5 for importance.

To promote and enhance the reputation of GB dairy, we need strong evidence to show our high standards of health and welfare.

We are well positioned to review non-commercial research to help the industry stay  at the forefront of global dairy production.

We help support the adoption of good practice through events, webinars and publications such as the Dairy Research Partnership review.

Johne’s disease is caused by a bacterium called Mycobacterium avium subsp. paratuberculosis (MAP). It leads to progressive wasting and increasingly severe diarrhoea.

Controlling the disease is difficult because the incubation period is long, often between three and five years.

This long duration between initial infection and onset of clinical signs means it’s hard to visually identify infection. Although many animals will test positive before showing any clinical signs.

As part of the AHDB-funded Dairy Research Partnership with University of Nottingham, Royal Veterinary College and Harper Adams University from 2011 to 2023, a series of Johne’s projects were undertaken and are summarised below.

This research has been embedded in the Action Johne’s training for vets to become BCVA Accredited Johne’s Veterinary Advisors (BAJVA).

Authors: Patterson, S., Bond, K., Green, M., van Winden, S. and Guitian, J.

Summary: The study followed 440 calves across 6 UK herds. Their dams were monitored for the presence of MAP using quarterly milk enzyme-linked immunosorbent assay (ELISA) tests. Researchers then completed statistical analysis to assess how and when the dam testing positive for Johne’s affected the calf’s likelihood of Johne’s infection.

Key messages:

• Cows may be transmitting the Johne’s bacteria (MAP) to calves earlier than previously thought
• Johne’s positive cows are 2.6 times more likely to have calves test positive than Johne’s negative dams
• Calves are more likely to test positive if their dam tests positive later in life, even if the dam was test-negative at calving
• Effective management of calves from Johne’s positive cows can significantly reduce the time needed to eliminate Johne’s
• When a cow tests positive for Johne’s, check if her calves are still in the herd and decide whether to manage them differently at calving and whether to breed replacements from them

Authors: Nunney, E., Crotta, M., van Winden, S., Bond, K., Green, M. and Guitian, J.

Summary: This study aimed to understand the relationship between bTB testing and ELISA milk tests for Johne’s disease. Data was provided by the National Milk Records group (NMR) and contained nearly 4 million milk test results from over 460,000 cows.

Key messages:

• There are small differences in the Johne’s milk ELISA results of ‘infected’ and ’non-infected’ cows following bTB skin testing
• ‘MAP-infected’ cows are more likely to test positive immediately after bTB testing. This is referred to as increased test sensitivity
• Non-infected cows are not more likely to test as a false positive after bTB testing
• The sensitivity of the Johne’s milk ELISA is increased shortly after a bTB test. However, it’s not fully understood what a post-bTB test positive means compared to a standard positive. The effect may also vary depending on herd prevalence
• The current recommendation is to leave 42 days between a bTB test and Johne’s test. If you want to use this research in your herd, consult your vet

Authors: Nunney, E., Crotta, M., Bond, K., van Winden, S., Green, M. and Guitian, J.

Summary: This study investigated an alternative method of classifying cows based on their likelihood of Johne’s infection. The aim was to improve decision making on individual cow management.

Key messages:

• The algorithm aimed to predict Johne’s status by using additional values such as age, time since last bTB test, herd prevalence and dam status, alongside milk test results
• This approach moves away from classifying cows strictly as either positive or negative and considers other factors that may affect test result patterns
• The result provided by the algorithm can be presented together with the HerdWise classification system. This allows for better interpretation of repeated tests and provides better support when making decisions on individual animals

Find out more about Johne’s by attending a discussion group or events in your area. Contact your regional Knowledge Exchange Manager to learn more.