Alberta groups keep eye on Johne’s disease

Prevention program | Alberta Milk wants producers to participate

RED DEER — About a quarter of Alberta dairy herds that were tested for Johne’s disease have the infection.

“Very likely half the herds in Western Canada have infection,” said Herman Barkema of the University of Calgary’s veterinary school.

Johne’s is an infectious, chronic inflammation of the gut caused by mycobacterium avium subspecies paratuberculosis (MAP). It is a major health concern for all domestic and wild ruminants.

“Every country that has dairy or beef cattle has Johne’s disease or has seen it,” Barkema said at the recent Western Dairy Seminar in Red Deer.

Alberta Milk introduced a voluntary surveillance and prevention program in 2010, which 40 percent of the province’s dairy herds have joined.

Preliminary results after one year found that about a quarter of the 219 herds involved in the program had a positive sample, which Barkema said is considered a low infection rate.

All the provinces but Saskatchewan have introduced similar programs in the last couple years.

The University of Calgary co-ordinates the program, working with breed associations and veterinary schools. About half the program funding came from the Alberta Livestock and Meat Agency.

Alberta Milk wants 80 percent enrolment by the end of this year, which it said would make it an effective program.

“If you want to control an infectious disease like this one, we want a really high participation rate,” Barkema said.

Herd veterinarians do the risk assessments and farmers are asked to select three improvements they can make on the farm.

Random manure samples are collected from the barn alleys and lagoons.

The project could eventually have a PCR test using DNA to check for the bacteria in bulk milk.

The disease is usually spread through manure from infected animals. It has been found in many herds where pooled colostrum was fed to calves. It was also more common when farms allowed unrestricted visitors to the barns or introduced new animals with unknown health status. Spreading manure on pastures where heifers grazed is another risk.

Barkema said it is a good idea to start testing calves when they are as young as 14 days because they can start shedding the bacteria within a couple months.

The disease acts slowly so poorer performing cows are often culled before they show symptoms.

The disease is ranked as a high level if one cow is diagnosed every one or two years on a farm. A moderate infection is one cow detected every four years and one positive cow every 10 years is considered a low rate of infection.

The U.S. Department of Agriculture calculated that nearly 70 percent of American farms were positive based on manure samples. The larger the farm, the greater the chance of finding the infection, partly because operations with more than 500 cows tend to introduce new stock that could be carrying the disease.

The presence of the MAP bacteria is also associated with Crohn’s disease in humans, but researchers do not know if they are correlated.

“The relationship between Johne’s disease and Crohn’s is not proven and if we are finding this bacteria, it doesn’t mean it causes the disease,” Barkema said.

“It could mean the gut of these people is so wrecked that every bacteria that you can think of easily colonizes.”

Alberta has about 15,000 Crohn’s patients with 800 to 900 new cases showing up each year. The incidence has been increasing since 1930.

A normal colon is smooth inside, but with Crohn’s disease, the interior is ulcerated. The disease causes pain, dizziness, vomiting, urgent diarrhea and weight loss. It most often affects those in the 15- to 25-year-old age group.

It’s not known if consuming dairy products spreads the disease, but Barkema thinks it is unlikely.

“Milk is a safe product. We need to guard it,” he said. “Milk is not the most likely vehicle.”

He thinks there could be a connection with farm run-off water flowing into drinking water. Chlorination does not seem to work against MAP.

However, there is no firm proof that water is the cause. Sick people may have instead been infected with E. coli bacteria, which also comes from manure.

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