Don’t Put Johne’s Prevention on the Back Burner

Thursday, June 18, 2026

Johne’s Disease still causing costly losses for producers

By Emily McKinlay

Johne’s disease has long been present on Canadian farms. While most producers have heard of Johne’s disease, many forget that it remains a major challenge affecting their herds.

Dr. Cheryl Waldner, a professor in the Department of Large Animal Clinical Sciences and the research chair in Beef Cattle Health at the University of Saskatchewan, says that Johne’s disease can be costly to beef producers even before the symptoms are recognizable.

“Johne’s disease (paratuberculosis) is an intestinal infection caused by Mycobacterium avium subspecies paratuberculosis (MAP). It thickens the intestinal wall, limits nutrient absorption, and leads to progressive weight loss, diarrhea, and ultimately death,” says Waldner.

“Animals showing clinical signs do not recover, and there is no known treatment. In beef herds, the most costly impacts are reduced weaning weights, delayed rebreeding, and cows being pre- maturely culled. These losses are largely driven by subclinical infections, which can go on in herds for years before they are recognized.”

Johne’s disease can affect beef cattle, dairy cattle, sheep and goats.

Current status

Johne’s disease is present on a significant number of both beef and dairy farms in Canada.

“The prevalence of MAP infection in beef herds was recently estimated at approximately three per cent in Eastern Canada and one per cent in Western Canada, with herd level prevalence — meaning one or more animals test positive — at approximately 15 per cent in the East and 10 per cent in the West,” says Waldner.

“As beef herds consolidate, there is a very real risk that the frequency of Johne’s disease in beef herds will continue to increase.”

Dr. Lisa Sharko, lead veterinarian in the Animal Health and Welfare branch of the Ontario Ministry of Agriculture, Food and Agribusiness, says that the dairy industry is also affected by Johne’s disease.

“A study done in 2018 sampling dairy cattle across Canadian herds determined that 54 per cent of Ontario dairy herds, 66 per cent of Western Canadian herds, 24 per cent of Quebec herds, and 47 per cent of herds in Atlantic Canada had Johne’s disease,” shares Sharko.

“In 2023, a follow-up was done testing Ontario bulk tanks, which found 40 per cent of herds were positive — a decline from 2018.”

Sharko says that she is concerned that Johne’s is a forgotten concern for many producers.

“There have been several testing and risk assessment management plan programs offered over the last couple of decades, but I do think Johne’s disease has slipped off people’s radar in the last several years,” says Sharko

“Recently, we have seen more producers putting a focus back on Johne’s disease testing and management, often triggered by the diagnosis of a positive animal.”

While Johne’s remains present in many herds, it can be difficult to identify and manage.

Identifying Johne’s disease

Animals infected with Johne’s disease can often appear unaffected while still spreading the infection.

“It is particularly tricky because infected cattle can show no signs of Johne’s disease for years while also still intermittently spreading it through the herd,” says Sharko.

“Signs to be on the lookout for in mature cattle are decreasing body condition and loose manure, which can be as severe as watery diarrhea.”

Waldner adds, “Cattle typically won’t show clinical signs of disease until they are at least two years of age and often much older.”

While clinical signs may not be visible, the infection still causes performance and economic losses. Sharko says that infected cows can have lower body weights and lower birthweights, with reduced pre-weaning gains. The cost of these losses is exacerbated by the current beef market prices.

“Calves from strong positive cows have up to a 21.48 kg decrease in 205-day adjusted weaning weights,” says Sharko.

“The negative impact on calf size and growth is possibly due to impaired nutrient absorption, decreased body condition score, and decreased milk production to sustain the calf. Johne’s positive dairy cattle have a 2.4 times increased risk of being culled, and their lactational 305-day milk production is decreased by at least 370 kg.”

Testing options are also a challenge for Johne’s disease, due to the cycle of the infection.

“No single test is perfect, especially early in the infection when the cow might not be shedding the bacteria or be shedding inconsistently, so we use a combination of tools,” says Waldner.

“Because the risk of false-negative results is high for animals in the early stages of disease for all tests, we focus on herd level testing strategies over a period of years. The Beef Cattle Research Council’s Johne’s Testing Decision Tool can help producers and vets compare test options, testing frequencies, and costs using western Canadian data.”

Testing and identification of animals is an important aspect of controlling Johne’s disease. If allowed to go on the back burner, costly performance losses can add up.

Managing Johne’s disease

Johne’s disease can be challenging to identify, but it can also be difficult to mitigate once it’s been detected.

Waldner describes a few of the barriers to identifying and managing the spread of Johne’s.

“First, Johne’s disease has a long incubation and intermittent shedding. As a result, infected cows and bulls can spread MAP for years before we can detect and cull them,” says Waldner.

“Second, the available tests miss early infections. Repeated testing over multiple years is necessary to identify infected animals. Thirdly, the MAP bacteria persist in the environment.”

MAP bacteria can persist in soil, water, or pens for months after the infected animal has been removed, prolonging the risk of infection. Most animals are exposed to Johne’s at a young age, when their immune systems are still vulnerable. It is often spread through the ingestion of contaminated manure. In beef herds, where calves are left with their dams, Johne’s can be transmitted through colostrum or milk from infected cows.

Sharko says this can make Johne’s management more difficult in beef herds than dairy herds.

“Dairy calves are often removed from dams quickly, separating them from the environment contaminated with MAP. They are often given colostrum replacement products or heat- treated colostrum, and are fed milk replacer or pasteurized milk, which all reduce the risk of transmission,” says Sharko.

“In beef calves however, calves remain with dams which keeps them exposed to MAP-infected manure in the environment. If a calf’s dam is infected, it is exposed to colostrum and milk, which may contain MAP.”

Waldner adds that if a cow’s infection has progressed and she begins showing clinical signs of Johne’s, there is also a possibility of transmission to the calf during gestation.

If a cow is suspected of being infected with Johne’s, it is important to take measures to limit the spread to other animals.

Waldner has a few recommendations for steps that producers should take to contain Johne’s as much as possible within their herd.

“Isolate suspect cows immediately to keep them out of calving areas and away from young stock. Engage your veterinarian to develop a herd level plan. Johne’s control is a multi year effort and works best when testing to identify infected animals and biosecurity are coordinated,” says Waldner.

“Protect calves first and minimize access to manure contaminated pens, feed, and water. Manage pen conditions to keep cow udders as clean as possible and manage colostrum to reduce contamination risks. Note that these are many of the same herd management strategies we use to reduce the risk of losses due to calf scours, where the problem bacteria and viruses are also transmitted through fecal contamination.”

She adds, “Finally, avoid feeding thin cows to gain weight before culling in any area used for calving or for housing cow-calf pairs.”

Preventing MAP bacteria from entering the herd is the best method for Johne’s prevention. Sharko says that, unfortunately, there is no vaccine to protect against Johne’s, so producers must focus on the ‘three pillars’ of prevention instead.

“The three pillars of Johne’s disease prevention are avoiding introducing MAP-infected cattle, removing cattle that are shedding MAP, and minimizing new MAP infections in calves,” says Sharko.

Waldner says that purchasing in cattle can be a major risk factor in introducing MAP bacteria.

“The biggest risk is purchased breeding stock from infected herds. When purchasing both replacement females and bulls, source animals from herds with health records and potentially testing information that support their Johne’s disease status,” says Waldner.

“Bulls, for example, are often purchased before they are old enough for a meaningful negative result on the individual animal.

“Talk to your veterinarian about whether pre-purchase testing might be useful for you.”

Waldner also recommends calving newly purchased animals separately from the main herd to limit exposure, avoid sharing equipment contaminated with manure, and protect water sources from manure contamination.

Waldner adds, “Rotational grazing systems and clean calving and nursery areas can help reduce exposure to infected feces.”

Johne’s continues to be a significant concern for the industry, prompting researchers to explore testing options, the disease cycle, and on-farm management.

“New research that was released in February on Canadian dairy farms found that MAP is shed earlier and seroconversion — the animal testing positive after exposure and presenting an immune reaction — can occur earlier in dairy heifers than previously assumed,” says Sharko.

“This is practical research that influences the inclusion of youngstock in Johne’s disease testing strategies.”

Waldner adds that the Beef Cattle Research Council has been developing a decision-making tool, using data from Western Canada, to help producers find a testing program that fits their herd structure and risk tolerance.

As Johne’s continues to present health and financial risks to the livestock industry, Waldner reminds producers to be mindful of biosecurity.

“Focus on biosecurity and calving-area hygiene to protect calves. Pair that with a multi year, risk based testing plan, and be disciplined about removing confirmed shedders as soon as possible and before they contaminate calving grounds,” says Waldner.

“The combination of buy smart policies and consistent on farm practices is our best option to keep Johne’s from becoming an entrenched, expensive problem.” BF