Dairy herd protected by a shield against Johne's disease

Is Your Dairy Herd at Risk? Understanding Johne's Disease Prevalence in Canada

Author's portrait.
Kai Mendoza in Health & Wellness June 2025 • 4 min read.

"A comprehensive study reveals the landscape of Mycobacterium avium subspecies paratuberculosis (MAP) infections across Canadian dairy farms, offering insights into regional variations, herd management practices, and effective control strategies."


Johne's disease, caused by Mycobacterium avium subspecies paratuberculosis (MAP), poses a significant threat to the dairy industry. This chronic intestinal inflammation in ruminants leads to reduced productivity and increased culling rates, resulting in substantial economic losses for farmers. Accurately assessing the prevalence of MAP infections is crucial for implementing effective control programs and monitoring their success.

Given the lack of standardized testing methods across Canada, comparing MAP prevalence among different regions and control programs has been challenging. A recent comprehensive study aimed to bridge this gap by estimating and comparing MAP prevalence in Western Canada, Ontario, Québec, and the Atlantic provinces, while also considering the influence of herd size and housing types.

This article distills the key findings of this nationwide study, providing dairy farmers, veterinarians, and industry stakeholders with valuable insights into the prevalence of Johne's disease in Canada. By understanding the regional variations, risk factors, and effective control measures, you can take proactive steps to safeguard your herd's health and productivity.

Key Findings from the Canadian Dairy Herd Study

Dairy herd protected by a shield against Johne's disease

The study, conducted on 362 dairy farms across all 10 Canadian provinces, involved collecting environmental samples and culturing them to detect MAP. One sample was taken from the lactating cow area, and another from the manure storage. In some cases, a third sample was collected from the area where breeding-age heifers were housed. Statistical analyses were performed to estimate the diagnostic sensitivity and specificity of these sampling methods and to determine the true prevalence of MAP infection.

Here's a breakdown of the most important findings:

  • Regional Prevalence: The true prevalence of MAP infection varied significantly across regions, with estimates of 66% in Western Canada, 54% in Ontario, 24% in Québec, and 47% in Atlantic Canada.
  • Housing Type Matters: Herds housed in tiestalls had lower MAP prevalence than those in freestall systems. This difference may be related to variations in animal contact, manure management, and overall hygiene.
  • Herd Size Impact: Larger herds (101-150 and >151 cows) exhibited higher MAP prevalence compared to smaller herds (≤100 cows), possibly due to increased within-herd transmission and the introduction of infected animals.
  • Environmental Sampling Effectiveness: Collecting two environmental samples (lactating cow area and manure storage) provided a sensitivity of 38% and a specificity of 100% for identifying MAP-positive farms. Including a third sample from breeding-age heifers did not significantly improve these values.
These findings underscore the importance of considering regional factors, housing systems, and herd size when assessing the risk of Johne's disease and implementing control strategies. By tailoring interventions to address specific risk factors, dairy farmers can minimize the impact of MAP infection on their operations.

Protecting Your Herd: Practical Steps for Johne's Disease Control

While the study provides valuable insights into MAP prevalence in Canada, it's essential to translate these findings into actionable strategies for protecting your dairy herd. Consult with your veterinarian to develop a comprehensive Johne's disease control plan tailored to your specific farm and management practices. Implementing effective biosecurity measures, optimizing manure management, and monitoring herd health are crucial steps in minimizing the risk of MAP infection and safeguarding the long-term productivity of your dairy operation.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is Johne's disease and what are its primary impacts on dairy farms?

Johne's disease is a chronic intestinal inflammation in ruminants, specifically caused by Mycobacterium avium subspecies paratuberculosis (MAP). Its primary impacts on dairy farms include reduced productivity in affected animals and an increase in culling rates. These factors lead to substantial economic losses for farmers due to decreased milk production and the premature removal of cows from the herd. Early detection and control are crucial for mitigating these impacts.

2

What were the key regional differences in Mycobacterium avium subspecies paratuberculosis (MAP) prevalence across Canada, as revealed by the study?

The study revealed significant regional variations in the prevalence of MAP infection across Canada. Western Canada had the highest prevalence at 66%, followed by Ontario at 54%, Atlantic Canada at 47%, and Québec with the lowest prevalence at 24%. These differences suggest that regional factors and management practices play a crucial role in the spread and control of Johne's disease.

3

How does housing type influence the prevalence of Johne's disease on dairy farms, according to the study?

The study found that the housing type significantly impacts the prevalence of MAP infection. Farms using tiestall systems demonstrated lower MAP prevalence compared to those with freestall systems. This difference could be attributed to various factors, including differences in animal contact, manure management practices, and overall hygiene levels within the different housing environments. The study indicates that farm layout and management have a bearing on the disease.

4

How effective were the environmental sampling methods in detecting Mycobacterium avium subspecies paratuberculosis (MAP) on farms, and what did the study determine?

The study evaluated the effectiveness of environmental sampling for detecting MAP. Collecting two environmental samples – from the lactating cow area and manure storage – provided a sensitivity of 38% and a specificity of 100% for identifying MAP-positive farms. Including a third sample from the breeding-age heifers did not significantly improve these values. This shows that while environmental sampling is useful, it may not identify all infected farms due to the sensitivity limitations. Farmers should use additional testing to monitor the herds.

5

What proactive steps can dairy farmers take to control Johne's disease on their farms, according to the study's recommendations?

The study recommends several proactive steps for dairy farmers to control Johne's disease. The primary recommendation is to consult with a veterinarian to develop a customized Johne's disease control plan tailored to the specific farm and its management practices. Implementing effective biosecurity measures, optimizing manure management practices, and consistently monitoring herd health are all crucial actions in minimizing the risk of MAP infection. Addressing these areas can effectively safeguard the health and productivity of the dairy operation.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.