Surreal illustration of a dairy farm with data-illuminated cows, symbolizing MAP infection prevalence.

Johne's Disease in Canadian Dairy Herds: What Farmers Need to Know

Samir D’Costa in Health & Wellness June 2025 • 3 min read.

"A comprehensive look at the prevalence, risk factors, and regional differences of Mycobacterium avium subspecies paratuberculosis (MAP) infections, empowering dairy farmers to protect their herds."

Johne's Disease, caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a persistent threat to dairy farms worldwide. This infection leads to inflammation of the small intestine in ruminants, causing chronic illness and economic losses due to reduced productivity and premature culling of affected animals.

Understanding the true prevalence of MAP infections is crucial for effective control and prevention. However, varying testing methods across different regions have made it challenging to compare infection rates accurately. Without consistent data, it’s difficult for farmers and veterinarians to implement targeted strategies.

A recent study across Canada aimed to address this gap by estimating and comparing MAP prevalence in different regions, herd sizes, and housing types. By using a standardized testing method, the study provides valuable insights for Canadian dairy farmers looking to protect their herds from Johne's Disease.

Key Findings: Regional Prevalence and Risk Factors

Surreal illustration of a dairy farm with data-illuminated cows, symbolizing MAP infection prevalence.

The study, encompassing 362 dairy farms across all 10 Canadian provinces, revealed significant regional differences in MAP prevalence. Environmental samples were collected from lactating cow areas, manure storage, and breeding-age heifer housing to detect the presence of MAP. These samples underwent rigorous testing to determine infection rates and associated risk factors.

True prevalence estimates varied considerably by region:

Western Canada: 66%
Ontario: 54%
Québec: 24%
Atlantic Canada: 47%

These findings highlight the importance of considering regional factors when implementing Johne's Disease control programs. Additionally, the study identified housing types and herd sizes as significant risk factors. Herds housed in tiestalls showed lower prevalence compared to freestall-housed herds. Larger herds (those with 101-150 and >151 cows) had higher prevalence than smaller herds (≤100 cows).

Protecting Your Herd: Practical Steps for Dairy Farmers

Understanding the prevalence and risk factors associated with MAP infections is the first step in protecting your dairy herd. By implementing targeted control programs, dairy farmers can minimize the spread of Johne's Disease and safeguard the health and productivity of their livestock. Stay informed, work closely with your veterinarian, and take proactive measures to ensure a healthy future for your farm.

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Everything You Need To Know

What exactly is Johne's Disease and how does it affect dairy herds?

Johne's Disease is caused by Mycobacterium avium subspecies paratuberculosis, often referred to as MAP. It leads to chronic inflammation of the small intestine in ruminants. This results in decreased productivity, weight loss and premature culling, causing significant economic losses for dairy farmers. The disease's persistent nature makes it a continuous challenge for the dairy industry.

Does the prevalence of Johne's Disease vary across different regions of Canada?

The study revealed that the prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) infections varies significantly across Canada. Western Canada showed a 66% prevalence, Ontario 54%, Québec 24%, and Atlantic Canada 47%. These regional differences highlight the need for tailored control programs that consider local factors and conditions.

Do herd size and housing types affect the likelihood of Johne's Disease?

Herd size and housing types can indeed impact the prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) infections. Larger herds, specifically those with more than 100 cows, tend to have higher rates of infection compared to smaller herds. Additionally, herds housed in freestall systems may experience higher prevalence compared to those in tiestall setups. Understanding these risk factors is essential for implementing targeted prevention strategies.

What practical steps can dairy farmers take to protect their herds from Johne's Disease?

To protect your herd, several practical steps can be taken. Understanding regional prevalence and herd-specific risk factors is crucial. Work closely with your veterinarian to implement targeted control programs, focusing on hygiene, biosecurity, and early detection. Regular testing can help identify and isolate infected animals, preventing further spread of Mycobacterium avium subspecies paratuberculosis (MAP).

What type of samples were collected from the dairy farms in the study?

The study used environmental samples, specifically from lactating cow areas, manure storage, and breeding-age heifer housing, to detect Mycobacterium avium subspecies paratuberculosis (MAP). These samples underwent rigorous standardized testing to determine infection rates. This method provides a comprehensive view of MAP prevalence across different areas of the farm, helping to identify potential sources of infection.