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Endangered black-footed ferret gets experimental COVID-19 vaccine in Colorado

In spring, when people first started worrying about what species besides humans could catch COVID, ferrets weren’t top of mind for most.

But while public health officials were still debating whether house pets were susceptible, a group of scientists in Colorado was working feverishly to save a species nobody was even sure was at risk: the black-footed ferret.

The reason for their concern? The black-footed ferret, already one of the most endangered mammals in North America, is a close cousin of the mink (both are members of the Mustelid family, which also includes badgers, otters, and wolverines). And farmed minks, bred for their sought-after fur, were proving to be highly susceptible to COVID transmitted by infected humans, leading to a high death toll in Utah mink farms as well as in Europe, where millions of minks were culled.

But in Colorado, scientists were trying to save a much smaller number: 120 black-footed ferrets were injected with an experimental COVID vaccine in the summer—months before US Department of Agriculture officials okayed applications for a commercial vaccine for minks. Thought to be extinct until 1981, the black-footed ferret was brought back from the brink of oblivion in the early 1980s, and even today, fewer than 300 are known to exist in the wild.

The 120 vaccinated ferrets—part of a captive population at the National Black-Footed Ferret Conservation Center (NBFFCC) outside Fort Collins, Colorado—represent nearly half of the known black-footed ferret population. The scientists behind the vaccination efforts are determined to ensure that COVID won’t claim them.

NEWStat talked to Tonie Rocke, PhD, a research epizootiologist with US Geological Survey, National Wildlife Health Center (NWHC), the scientist who helped develop the vaccine, to find out more.

NEWStat: What inspired you to work on a vaccine for black-footed ferrets, given that there are no documented cases of COVID-19 in the species?

Tonie Rocke: Early in the pandemic, we learned that domestic ferrets were susceptible to the virus that causes COVID-19. The US Fish and Wildlife Service (USFWS) staff that manages the captive black-footed ferret breeding colony at the NBFFCC became concerned about the possibility of COVID 19 exposure in this colony and transmission back and forth between the ferrets and their human caretakers. That concern was amplified when we learned about the outbreaks of COVID-19 in captive minks. Although the USFWS immediately instituted policies to minimize the risk of exposure to both humans and ferrets, we started thinking about the possibility of vaccinating the animals as an added precaution. Laboratory studies in mice and hamsters had shown that vaccination of animals with the spike protein of the coronavirus could protect them from disease.

NEWStat: Given the ravages that COVID has taken on the mink population in both Europe and the US, why have you focused so much attention on vaccinating black-footed ferrets?

TR: The mission of the [NWHC] is focused primarily on wildlife health, particularly as it relates to conservation. There are only about 280 black-footed ferrets in captivity and the captive breeding and reintroduction program is critical to the recovery of this species. NWHC has been assisting with disease issues in black-footed ferrets for many years; thus, we were in a position to support the efforts to minimize the risk of COVID-19 occurring in the captive population.

NEWStat: How did you go about developing the vaccine?

TR: We did not develop a new vaccine per se; instead, we took advantage of commercially available purified SARS-CoV-2 spike protein. We combined it with an adjuvant used previously in black-footed ferrets and conducted a small experimental trial, confirming this vaccine preparation was safe for the animals and elicited a rise in virus-neutralizing antibody titers.

NEWStat: How will you know whether the vaccine is effective, and what are your next steps?

TR: We are planning to conduct additional assays to determine if the immune response of vaccinated ferrets is actually protective. The USFWS is actively monitoring the animals for any signs of disease, and one group of controls has been left unvaccinated. If disease occurs, additional samples will be collected, and the course of disease will be documented and compared between vaccinated and unvaccinated ferrets.

NEWStat: To date, how many black-footed ferrets have caught COVID?

TR: To our knowledge, the black-footed ferret colony has not been exposed to the virus—and we hope they never are.

Photo credit: Ryan Hagerty, USFWS