As the coronavirus pandemic continues, we’re learning more about the risks, not just for humans, but also for animals. Mink have proven especially susceptible to the virus: SARS-CoV-2, the animal virus that causes COVID-19 in humans, has been showing up especially in mink being farmed for their pelts.

Now, it’s shown up on a mink farm in Oregon.

The spread of coronavirus among mink has been a major problem in European countries such as Denmark and the Netherlands, where outbreaks of the virus on mink farms have led to the killing of millions of animals. Mink farm outbreaks have been reported in several pelt-producing states in the U.S. as well. In late November, Oregon health and agriculture officials announced a confirmed outbreak among mink and humans at one of the state’s 11 mink farms. The state has declined to disclose the location of the affected farm in Oregon, citing medical privacy laws. That decision has been criticized by environmental advocates, who’d warned of the potential for such an outbreak in Oregon just weeks ago.

One of the people leading Oregon’s response to the farm outbreak is Dr. Ryan Scholz. He’s the Oregon Department of Agriculture’s state veterinarian, and it’s his job to prevent or mitigate the spread of diseases among the state’s livestock. Scholz talked with OPB recently about how he’s responding to the outbreak.

How did mink get the virus?

Scholz said much is still unknown about why mink in particular are so vulnerable to SARS-CoV-2, beyond that mink and other species in the mustelid family — which also includes ferrets and otters — have “remarkably similar body systems” to humans.

But it is known how these mink originally got the virus: from humans.

“People who were associated with this farm picked up the virus somewhere in the community … and then brought it back to the farm with them,” Scholz said.

Farm employees were wearing personal protective equipment at work, he said, but the virus still made it into the mink.

According to a timeline of the outbreak provided by the department, the farm’s owner first reported on Nov. 19 that he was symptomatic himself and was being tested. He tested positive the following day.

“He was very proactive and did all the right things with this,” Scholz said.

Scholz kept in touch with him over that weekend. Several days later, on Nov. 23, the farmer reported some of the mink were exhibiting symptoms of the virus, too, including coughing and sneezing.

“We immediately made plans: I drove out there the next morning first thing, and we tested a number of mink on the farm,” Scholz said.

Testing and quarantine

A sample of 10 mink that were showing symptoms, of the farm’s approximately 12,000 animals, were chosen to be tested. Scholz said the tests for mink, besides being administered orally rather than nasally, are the same those for humans.

The test samples were sent to the Oregon Veterinary Diagnostic Laboratory at Oregon State University, which has been running both human and animal tests for the coronavirus this year. After being run at the Oregon lab on Nov. 25, the samples were sent to the United States Department of Agriculture’s national veterinary lab in Iowa, which confirmed the results on Nov. 26: all 10 animals tested positive for SARS-CoV-2. The outbreak on the mink farm was announced to the public the following day.

“The farm is under quarantine,” Scholz said. That means neither animals nor animal products can leave the farm. “It was placed under quarantine immediately as soon as any symptoms were reported in the animals,” on Nov. 23.

Meanwhile, the Oregon Health Authority tested farm staff for COVID-19 the day after the farm’s owner reported his own positive test. OHA’s public health veterinarian, Dr. Emilio DeBess, directed the farmer and staff to self-isolate that same day, Nov 21.

Scholz said that, under the quarantine orders, he is the only person permitted to go onto the farm other than its staff, and only while wearing full personal protective equipment.

Testing will continue at two-week intervals as necessary: Scholz planned to return to the farm to test more mink for the virus on Monday, in order to see if the virus has cleared from the herd. A significantly larger number of mink will be tested this time, he said.

“Then, if any virus is still found in that sample, we’ll continue testing. We’ll actually continue testing until we have two sets of samples that are all negative before we release the quarantine, so we know for a fact that there is no more virus on that farm,” Scholz said.

Scholz said virus symptoms in the farm’s mink appear to have resolved within a few days of initial signs of infection. He added that no deaths of mink due to the virus have been reported on the farm.

What about Oregon’s other mink farms?

Just weeks before this outbreak was reported, the environmental group Center for Biological Diversity sent a letter to officials with the Oregon Department of Agriculture and the Oregon Health Authority warning of the “urgent public health threat” of coronavirus transmission on Oregon’s mink farms, similar to what’s been seen in Europe and elsewhere in the United States.

“We therefore strongly request that you immediately send inspectors to all mink-rearing facilities, starting with the ones containing the largest concentration of animals, to conduct an investigation and ensure that these facilities do not imperil public health,” the letter read.

But Scholz said the Oregon Department of Agriculture is not currently doing surveillance testing for the coronavirus at other mink farms in the state.

“The USDA and the CDC have advised against it for a number of different reasons, not the least of which, for us to go onto those farms and do that testing, it actually poses a pretty high risk of introducing the virus onto the farm,” Scholz said.

He noted that in Oregon, the coronavirus is a reportable disease, meaning it’s legally required to report it in animals.

“In this case, the system worked perfectly. The farmer reported it within hours of noticing symptoms. We were able to get a quarantine on. We were able to get the diagnosis made,” Scholz said. “That is our normal system for any of these kinds of diseases in livestock.”

The Center for Biological Diversity has continued to call for inspection of other Oregon mink farms. In a more recent letter following the state’s announcement of the outbreak, the group advocated for state agencies not only to do more widespread testing of mink, but also to quarantine all mink farming operations in the state, halt breeding programs, and coordinate a government buy-out program of the state’s mink farms. It also criticized the state’s lack of disclosure of the location of the affected farm, writing that details of Oregon workplace outbreaks are often made publicly available, and that such data is essential to public efforts to contain the spread of COVID-19.

Scholz and DeBess wrote in a response that the Oregon Health Authority followed all COVID-19 reporting protocols and state privacy laws. They said that, while the agency does report some workplace outbreaks, it “does not release any information that could potentially identify personal details of anyone connected to an outbreak.” They added that details of the outbreak in mink were “withheld due to biosecurity concerns.”

On Dec. 8, the animal rights activist group Direct Action Everywhere claimed it had discovered the location of the mink farm where the outbreak occurred; the group identified it as the Western Star Fur Farm in Astoria. The group said in a release that activists used drones and hidden cameras to surveil the state’s 11 mink farms for activity to indicate follow-up testing. The Oregon Department of Agriculture said it cannot confirm the information the group is sharing, and again declined to release the name and location of the farm. The department reiterated that doing so would lead to the release of medically identifiable information.

Can Oregon avoid Denmark’s fate?

The most severe consequences of coronavirus transmission between humans and mink have been seen in Denmark. First of all, in Denmark as well as the Netherlands, there have been multiple cases where mink which have caught the coronavirus from humans have then passed it back to additional, previously uninfected humans.

Scholz said that no such cases have been documented in the United States, despite multiple outbreaks on domestic mink farms. The Centers for Disease Control and Prevention has maintained that there’s no evidence that animals play a significant role in spreading SARS-CoV-2, and the risk of animals spreading it to humans is low. But, Scholz said, it’s still a concern in the United States, and is being watched for.

“That’s really what our response is based around. It’s around ensuring that no one else goes onto this farm, that anyone who is on the farm is wearing an even higher than normal level of PPE, and that there are no opportunities for the virus to possibly go from the mink back to people,” he said.

Even more alarming is that, in Denmark, some mink have been found to be infected with a mutated strain of the coronavirus that can spread to humans. At least 12 people in Denmark tested positive for the new mutated virus. It’s caused fear that the unique variant, known as the “cluster 5” variant, could undermine the efficacy of COVID-19 vaccines. That risk led Denmark’s government to take the extreme step of killing its entire population of mink, as many as 17 million animals.

However, the cluster 5 variant has not been discovered outside of Denmark. Scholz said that the test samples of infected mink in the Oregon farm outbreak were confirmed on Nov. 30 by the USDA veterinary lab not to contain the mutated variant.

Scholz was hopeful that ongoing prevention efforts would keep Oregon from getting to the point where mink would be killed en masse, like what happened in Denmark. He underscored the fact he and other state veterinarians in the U.S. have been working closely with mink producers to ensure that they are aware of the necessary biosecurity measures on their farms, that they have adequate masks and other PPE, and that they’re following CDC guidelines.

“This is something that we as a state have been preparing for for a long time,” he said. “Those plans were put into play here, and they, by all measures, are working and have been successful at preventing this disease from moving beyond this farm where we found it.”

Should people be worried about their companion animals?

Mink aren’t the only animals at risk of contracting SARS-CoV-2. There have been a number of cases of the virus reported in other animals in the United States.

The virus has been found “in dogs and cats, and probably most notably, the lions and tigers on exhibit at the Bronx Zoo, early on in the virus,” Scholz said.

But there have not been any cases documented in the United States so far in which the virus has moved from an animal back to a human.

“I don’t think that there’s any risk that, you know, your dog is going to give you COVID-19. The risk really is more: if you are experiencing symptoms that may be associated with COVID-19 … while you’re self-isolating from the general public, you should also be trying to isolate from your dog as well,” Scholz said.

He noted that the CDC has put out helpful guidelines on caring for pets if you have tested positive for the virus.

“We know that it is possible — it’s rare, but it can happen. It’s been documented to happen a number of times, where pets have contracted the virus from their owners when their owners were sick.”