Bovine leukosis increasing in prevalence

Veterinarian says dairy farms are more prone to the easily managed disease, but it likely also exists on beef operations

Some veterinarians are hoping they can help producers better manage bovine leukosis, a disease that can rob productive animals on dairy and beef farms.

The disease stems from a viral infection that’s easily spread through blood, milk and colostrum, affecting the immune system and potentially causing tumours.

Frank van der Meer, a veterinarian and associate professor with the University of Calgary who specializes in the disease, said it can cause early mortality.

“It’s not a pretty sight to have cases on your farm. It’s not what you farm for,” he said.

“It has negative impacts to health, and it can become a welfare issue, considering tumours in a cow are welfare issues, so we want to address that.”

The disease is growing in prevalence and is well known in dairy farms, van der Meer said.

Almost 95 percent of dairy operations in Canada are infected to some degree, he added.

“It means almost every dairy farm in Canada is infected with it and sometimes it’s 70 per cent of their herd,” he said.

Van der Meer said there is no data on the number of infected beef cattle in Canada, but he believes it exists in some herds.

Other figures show 30 percent of beef cattle are infected in the United States, he added.

“I would bet a good bottle of whiskey that it’s in beef herds here.”

He said the best way for beef and dairy producers to handle bovine leukosis is by implementing best management practices.

Dairy producers will likely have to be more rigorous given the makeup of their farms, but they both should first create an inventory of their animals, determining which ones are problematic.

Following that, he said, mitigation methods include:

  • Freezing, pasteurizing or using powdered colostrum.
  • Avoiding the use of milk that comes directly after colostrum from infected cows.
  • Changing needles to avoid cross-contamination between infected and non-infected animals.
  • Changing gloves during pregnancy checks.
  • De-horning with high-heat or electric dehorners, which disinfect.
  • Disinfecting tools such as hoof-trimming knives and teeth-removal instruments between animals to avoid cross-contamination.

He said the same strategies generally apply to beef producers, though they might not need to be as rigorous given the nature of their farms.

As well, contamination through colostrum and milk is largely unavoidable for cow-calf producers.

“If a calf is suckling from its infected mother and taking the colostrum, then most likely the calf will be infected, too,” van der Meer said.

“Colostrum is a major root of infection to the next generation.”

He said he hopes Canada can see reductions in bovine leukosis in about 10 years, but added he’s not optimistic changes will happen quickly.

“I think some are motivated and they will succeed, but there is no obligation to get rid of it in Alberta or Canada, and it would take stricter control measures or lots of peer pressure from farmers and vets to see quick action,” he said.

Australia, New Zealand and countries in Europe have managed to eradicate the disease through animal destruction, but van Der Meer said those nations caught it when prevalence was low.

In Canada, he said, prevalence of the disease is too high to take extreme destruction measures.

“Given the high statistics, you can’t ask a farmer to eradicate. That doesn’t work.”

However, van der Meer and other veterinarians are increasing their efforts to educate producers about the disease, motivating them to undertake best management practices.

The University of Calgary’s Faculty of Veterinary Medicine is also currently working on a project to identify any bottlenecks with the disease, figuring out what hurdles need to be overcome.

“Managing this is not rocket science. It is easy to do,” he said.

“We are trying to show that there are logical steps to this. Over time, hopefully we’ll see more people motivated in controlling this disease.”

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