ASF battle continues to focus on biosecurity

A vaccine remains the ultimate goal but is still years away, so emphasis remains on strengthening detection and defence

While African swine fever remains clear of Canadian shores so far, it’s on the minds of producers as well as researchers racing to develop protocols and ultimately a vaccine.

“Canada exports two out of every three pigs,” said Andrew Van Kessel, associate director of research at the Vaccine and Infectious Disease Organization-International Vaccine Centre (VIDO-InterVac).

“That has tremendous implications for the industry.”

One positive test and the borders of importing countries slam shut to an annual trade of $4 billion in Canadian pork, according to the Canadian Food Inspection Agency.

This country is among the world’s top three pork exporters, supporting more than 100,000 jobs and collectively adding $24 billion annually to the economy.

“That would be catastrophic,” Van Kessel said.

“I think that’s probably keeping up a few producers at night these days.”

ASF doesn’t affect humans but it is lethal to pigs. It’s persistent, able to survive up to six months in some cured meats, according to information from the Canadian Pork Council. One bright spot is that it doesn’t easily spread.

“African swine fever, although it’s extremely lethal, is not very infectious. It moves like molasses in January where as PED virus moves like water in July,” said Dr. Egan Brockhoff.

Brockhoff, who farms, operates a veterinary practice in Red Deer and is veterinary counsellor for the pork council, said ASF has been on the radar in North America for the past few years with co-ordinated planning among Canada, the United States and Mexico on how to keep it out or deal with it if it manages to break onto the continent.

He said the council has also been working with the CFIA and Canada Border Services Agency on prevention and emergency operations planning.

The council is working with a group of veterinarians and industry representatives to develop training tools and videos to teach biosecurity best practices and posting them online. This includes protocols for smallholders who may keep their animals outside and in potential contact with feral wild boar.

ASF is present in wild boar in Europe, and the animals can pass disease to their domestic cousins.

Other resources include a 160-page “bible,” originally developed for British Columbia’s small-scale producers, which is now being adapted for use across the country. Enhanced biosecurity protocols for larger producers have also been put in place.

Ultimately, the ASF threat won’t abate until there is a vaccine, a task that in Canada falls to government labs and VIDO-InterVac. The organization received approval from the CFIA in January to work with the ASF virus — the first non-governmental organization in the country to do so.

One challenge is there must be a way to tell if animals have been vaccinated or infected.

“That’s critically important in North America where we do not have the disease,” Van Kessel said. “We would want to be able to firmly establish that an animal was vaccinated versus one that was exposed.”

The trick is to produce a “differentiating infected from vaccinated animals” vaccine. Such a product stimulates the immune system to produce antibodies that protect against the disease, but are different enough to be identified as coming from the vaccine.

The approach at VIDO-InterVac was to insert ASF genes into an adenovirus, one of a group of common viruses that infect airways and lungs. The research team had just started testing the approach, with limited success, when another virus arrived: SARS-CoV-2, the agent responsible for COVID-19.

All hands were suddenly on deck to respond to the worldwide human disease pandemic. VIDO-InterVac, which houses the largest containment Level 3 laboratories in the country, was suddenly front-and-centre in Canadian efforts to develop a vaccine and to support similar efforts elsewhere. Van Kessel said this is precisely the crisis the national facility was built to meet, but it did present challenges for the ASF project.

While there is ample Level 3 lab space, people to work in it remain in short supply.

“The people trained to work in there, both with animals, the disease models, and laboratory work — we’ve been growing the numbers and training folks up but it takes time,” Van Kessel said.

So the ASF project shunted its focus to another track.

To develop a vaccine against a virus, researchers must be able to grow that virus in quantity for testing. This is notoriously difficult for ASF. The virus can be grown in the lab, but only in a type of immune system cell called aveolar macrophages.

These cells must be collected from living animals and they don’t last long in the lab. The research team is working to develop cell lines that can be cultured outside of the animal and are effectively immortal — that is, they will keep on dividing indefinitely. Since such work doesn’t require a high containment facility, it can keep the ASF vaccine project progressing, while potentially helping vaccine development teams around the world.

While work is ongoing, Van Kessel said it is unknown when an effective ASF vaccine might be widely available.

“Right now, it’s about keeping the darned virus out,” he said. “And planning for what we do if it gets in.”

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