A study beginning in January at the University of Saskatchewan’s Livestock and Forage Centre of Excellence will work toward better diagnostics and a vaccine for tuberculosis in bison.
Dr. Todd Shury, wildlife veterinarian with Parks Canada, said the official caudal fold test under the animal’s tail is typically used, especially when they are exported, but it is stressful and presents a lot of false negatives.
There has been little work done on TB in bison, except for one study in 1988, he told producers at the Canadian Bison Association annual meeting.
Read Also
Beef check-off collection system aligns across the country
A single and aligned check-off collection system based on where producers live makes the system equal said Chad Ross, Saskatchewan Cattle Association chair.
Parks Canada identified bison diseases as an area to work on after concerns about the future of Wood Buffalo National Park’s status as a UNESCO Heritage Site. The department wanted to look at cumulative impacts on the park, and brucellosis and TB in bison were targeted for more research.
Both diseases are found in the park but have not been known to infect any cattle herds because of distance.
The research aims to answer several questions:
- Is the Wood Buffalo park strain of bovine TB more virulent or infectious than other reference strains of bovine TB?
- Does the experimental infection mimic what we see in naturally infected populations in Wood Buffalo National Park?
- How well do current tests that don’t involve skin tests work?
A mouse trial was recently completed to help answer the first question.
“It appears that the Wood Buffalo isolate is just slightly less virulent than the reference strain, which is a bovine TB strain,” Shury said.
But that isn’t surprising because the host is meant to be a bison and not a mouse.
In January, 18 seven-month-old bison calves will be infected to see if an experimental infection model can be developed. They will receive two different doses of the strain isolated from Wood Buffalo park to find out which mimics natural infections. They will be euthanized to see if lesions developed and diagnostic tests are positive.
The work will be done at the LFCE under VIDO-InterVac.
“This will actually be the first time bison will have been held in containment level 3 in Canada. It will be the first time that animals have actually been challenged experimentally with this Wood Buffalo strain of TB,” Shury said.
The following year, 24 cows and calves will be vaccinated with the BCG vaccine familiar in human use and a vaccine developed in Spain for use in feral pigs. Then, a similar trial will be carried out.
“We’re hoping we can find a vaccine…that we could eventually take to the field,” he said.
Other countries use oral vaccines to deliver protection to wild host populations, such as possums in New Zealand, the European badger in Europe and feral pigs in Spain, and Shury said that could be an option for bison.
The diagnostic test experiments will examine six options. Promising options would be taken to Wood Buffalo National Park to see how they work on naturally infected animals. Shury said typically vaccines don’t work as well in a natural infection.
The tests would be taken into a known negative population of 200 to 300 bison to see how many false positives occur. The herds in Elk Island and Grasslands national parks are known to be clean and Shury said Parks Canada is negotiating with the Canadian Food Inspection Agency to test animals going to slaughter from some private herds in the Saskatoon area.
“If we can find one of these tests that has fairly high sensitivity and high specificity we could potentially go into Wood Buffalo National Park and some of these infected herds, remove infected animals, and if you do that enough over a longer period of time that will reduce the prevalence of disease.”
Shury added there are good tests available for brucellosis and a good vaccine could prevent infection in disease-free herds that are at risk.
TB-infected bison face a greater risk of death during winter, mostly in adult females.
Shury said TB seems to have little effect on reproduction.
Clinical signs are often absent until the very late stage of the disease.
“You could have it in your herd and not know it unless you are routinely sending animals to slaughter or testing them,” Shury said.
The problem with TB comes when exporting.
“It’s a trade thing,” Shury said. “(Being TB-free) does give Canada an economic advantage in trading with other countries.”
