Study suggests TB vaccine could help the North’s wood bison

A new study suggests a vaccine could help control bovine tuberculosis among bison in Wood Buffalo National Park.

The authors of the paper, published in the peer-reviewed journal Scientific Reports late last month, explores whether two vaccines – Bacille Calmette-Guérin, or BCG, and heat-inactivated Mycobacterium bovis, or HIMB – could effectively protect wood bison against bovine TB.

Researchers at Parks Canada and the University of Saskatchewan found that bison who received either vaccine had fewer lesions in their lungs, meaning they were less likely to be infectious. Bison that received the BCG vaccine, in particular, showed significantly reduced risk of spreading the disease.

“We were quite excited that this vaccine seems to offer a fair bit of protection to reducing the infectiousness of bison,” said Todd Shury, one of the study’s authors who is a wildlife veterinarian with Parks Canada and an adjunct professor at the University of Saskatchewan’s Western College of Veterinary Medicine.

“Over time, if you were to use it in an infected population, you could reduce the prevalence of that disease quite significantly in a population.”

Bovine TB is an infectious disease that could pose a threat to the conservation of wood bison and presents a risk to domestic cattle. In Canada, the study states, the disease has been reported in elk, moose, mule deer, wolves and bison.

Shury said bison in and around Wood Buffalo National Park are prone to infection from both bovine TB and bovine brucellosis, also known as Bang’s disease. He called the bison “one of the last reservoirs of these two diseases in Canada.”

“They represent a risk to the domestic cattle industry but also to disease-free herds that exist and have been reintroduced in the Northwest Territories, Yukon, northern British Columbia and Alberta,” he said.

Shury said bovine TB and brucellosis can also be transmitted to people when they butcher an infected animal or eat meat that is not well cooked. He said, however, that as far as researchers are aware, neither disease has been transmitted to humans in and around Wood Buffalo National Park “despite the fact that people have been eating those bison for at least 100 years or so.”

Shury said there have been cases where people have been exposed to brucellosis from eating caribou farther north.

While culling has been used to control and eradicate bovine TB in some species, the authors of the study said more effective and socially acceptable control strategies are needed.

Wood Buffalo National Park, which straddles the NWT-Alberta border, is home to around 3,000 wood bison – the largest free-roaming, self-regulating wood bison herd in the world.

Wood bison, which are economically and culturally important to Indigenous people in the region, are considered threatened under the NWT and federal species at risk acts.

According to the study, bovine TB was likely inadvertently introduced to the park in the 1920s when infected plains bison were moved there from Buffalo National Park – a similarly named but entirely different park in Alberta that no longer exists.

The disease is now endemic in the wood bison population in Wood Buffalo National Park.

How researchers studied the vaccines

While oral TB vaccines have proven to be effective in European badgers, brush-tailed possums, wild boar and deer, Shury said there has been limited research on the use of such vaccines for bison.

“With wild bison, it’s much easier to give them an oral vaccine through feed or something like that than to try and capture a large proportion of the population and inject a vaccine,” he said.

Shury explained that the BCG vaccine has been widely used to protect humans against TB for more than 100 years. He said studies indicate HIMB, which has been used in the past 10 to 15 years, is effective at protecting several animal species from TB.

To test the effectiveness of the vaccines in bison, researchers infected young bison from Alberta’s Elk Island National Park – which are known to be free of TB and brucellosis – with a strain of TB isolated from a diseased bison in Wood Buffalo National Park. They then assessed how well the vaccines protected the animals by examining their lymph nodes and lungs. Shury said the test bison had to be “humanely euthanized” for that assessment as researchers don’t have good tests for TB in live animals.

“This is the first time that’s been done with bison in Canada,” he said of the study.

Shury said the research was conducted in collaboration with the Vaccine and Infectious Disease Organization at the University of Saskatchewan, which has one of Canada’s only containment level three facilities – a designation for places where dangerous biological agents can be safely handled – that can also house large species such as bison. He said the bison had to be contained to prevent the risk of the disease spreading to cattle.

Researchers studying TB and brucellosis vaccine

Shury said researchers at the Bison Integrated Genomics Project have developed a BCG vaccine that can protect against both TB and brucellosis. Preliminary results from a 2024 trial of the vaccine indicate “it’s going to work fairly well,” he said.

Shury said the next step will be looking at how the vaccine works in a naturally infected population and studying methods of delivering the vaccine to a large proportion of bison. He said you typically need to vaccinate about 80 percent of a population to get a significant effect.

“We’re really excited that this offers a new way to manage these diseases in northern Canada around Wood Buffalo National Park without having to kill all the animals in the park, which is one of the only solutions that’s been proposed to date,” he said.

“This gives us an alternative management tool to potentially protect non-infected herds from becoming infected and potentially reduce the prevalence of some of the infected herds.”