A sign calling for the protection of ostriches at the Universal Ostrich Farms is displayed at the farm in Edgewood, B.C., on Saturday, May 17, 2025. THE CANADIAN PRESS/Aaron Hemens

An affidavit by Canada's deputy chief veterinarian says new analysis has confirmed ostriches at a British Columbia farm that is fighting a cull order for its flock were sickened by a unique and more lethal strain of the avian influenza virus.

The affidavit by Dr. Cathy Furness with the Canadian Food Inspection Agency says further investigation of samples taken from the birds revealed the "novel reassortment" of the virus has "enhanced the pathogenicity" of the strain.

The strain was "among the most virulent" tested at Canada's National Microbiology Laboratory and even low doses killed mice within a few days, the document says.

But Furness says the CFIA doesn't know how likely it is that the ostriches at the Edgewood, B.C., farm remain infected, or will become infected.

The document was filed on Tuesday with the Federal Court of Appeal, where the agency is arguing against another stay delaying the cull of about 400 ostriches.

Katie Pasitney, farm spokeswoman and daughter of its co-owner, says in a Facebook post they are "actively responding" to filings by the Justice Department.

"We are putting in our reconsideration material as well," she says in the post on Wednesday, adding the farm would be providing further updates.

The farm's owners have long said the flock is healthy, acquiring "herd immunity" since the CFIA ordered the cull on Dec. 31, 2024, during an outbreak that went on to kill 69 birds.

Furness's filing follows a Federal Court of Appeal ruling granting the farm an interim stay and delaying the cull as it seeks a hearing at the Supreme Court of Canada.

She says the new information "increases the potential animal and human health risks associated with the ongoing delay" and "decontamination" of exposed areas.

Furness says a review of scientific literature and information from a veterinary epidemiologist with the federal agency show ostriches can shed large amounts of avian influenza and continue shedding without showing signs of infection.

"That is, infected ostriches may still be shedding virus through their urine, feces, and respiratory secretions, despite appearing healthy. This is referred to as 'silent shedding', which is also observed in some other birds, like ducks," the filing says.

Universal Ostrich Farms has repeatedly called for testing to determine whether the birds are infected with H5N1.

Furness says the chances they are infected or will become infected "is unknown by CFIA, due to gaps in the available science regarding how long immunity to (avian influenza) viruses may last in an individual ostrich," as well as a lack of information about how many ostriches were infected during the original outbreak.

The affidavit says the requirements for a cull were met on Dec. 31, 2024, "and the policy does not provide for additional testing."

In any case, Furness says, testing could only provide additional evidence of current risk. It would not address the unknown risks of reinfection or the risks associated with the "contaminated environment," she says in the document.

Furness says the CFIA's risk assessment is also informed by the farm owners' "inability or unwillingness" to comply with quarantine rules.

Avian influenza viruses can survive for months or even years in fresh water at low temperatures and have been documented surviving in manure and on feathers in low temperatures for about four to six months, the affidavit says.

"Therefore, a source of infection or reinfection with (avian influenza) can remain in the environment long after individual infected birds have recovered," it says.

Universal Ostrich Farms has maintained the birds should be spared because they are scientifically valuable and pose no threat.

The farm has lost in Federal Court and the Federal Court of Appeal, but last Thursday its lawyer sought another stay on the cull order, filing a series of documents as the farm pursues a hearing in Canada's High Court.

In a decision dated Sept. 6, the Appeal Court granted the interim stay until the stay motion "is decided on the basis of a full record."

The interim stay motion says the farm was to have until Wednesday to respond to the latest filings by the CFIA.

It says the agency is still allowed to take preparatory steps to kill the birds.

The CFIA says on its website that allowing a flock previously exposed to avian influenza to remain alive means a potential source of the virus persists and increases the risk of reassortment or mutation of the virus.

The farm's situation has drawn attention from officials in the administration of U.S. President Donald Trump, including Health Secretary Robert F. Kennedy Jr., who has repeatedly called for the animals to be spared and studied. Supporters seeking to avert a cull have also been camping out at the farm and staging concerts.

This report by The Canadian Press was first published Sept. 10, 2025.

News from © The Canadian Press, 2025