In late summer, as researchers accelerated the first clinical trials of COVID-19 vaccines for humans, a group of scientists in Colorado worked to inoculate a far more fragile species.
About 120 black-footed ferrets, among the most endangered mammals in North America, were injected with an experimental COVID vaccine aimed at protecting the small, weasel-like creatures rescued from the brink of extinction four decades ago.
The effort came months before U.S. Department of Agriculture officials began accepting applications from veterinary drugmakers for a commercial vaccine for minks, a close cousin of the ferrets. Farmed minks, raised for their valuable fur, have died by the tens of thousands in the U.S. and been culled by the millions in Europe after catching the COVID virus from infected humans.
Vaccinating such vulnerable species against the disease is important not only for the animals’ sake, experts say, but potentially for the protection of people. Some of the most pernicious human diseases have originated in animals, including the new coronavirus, which is believed to have spread from bats to an intermediary species before jumping to humans and sparking the pandemic.
The worry when it comes to animals like farmed minks, which are kept in crowded pens, is that the virus, contracted from humans, can mutate as it spreads rapidly in the susceptible animals, posing a new threat if it spills back to people. Danish health officials in November reported detecting more than 200 COVID cases in humans that had variants associated with farmed minks, including a dozen with a mutation scientists feared could undermine the effectiveness of vaccines. However, officials now say that variant appears to be extinct.
In the U.S., scientists have not found similar COVID mutations in the domestic farmed mink populations, though they recently noted with concern the discovery of the first case of the virus in a wild mink in Utah.
“For highly contagious respiratory viruses, it’s really important to be mindful of the animal reservoir,” said Dr. Corey Casper, a vaccinologist and chief executive of the Infectious Disease Research Institute in Seattle. “If the virus returns to the animal host and mutates, or changes, in such a way that it could be reintroduced to humans, then the humans would no longer have that immunity. That makes me very concerned.”
For the newly vaccinated ferrets, the main risk is to the animals themselves. They’re part of a captive population at the National Black-footed Ferret Conservation Center outside Fort Collins, Colorado, where there have been no cases of COVID-19 to date. But the slender, furry creatures — known for their distinctive black eye mask, legs and feet — are feared to be highly vulnerable to the ravages of the disease, said Tonie Rocke, a research scientist at the National Wildlife Health Center who is testing the ferret vaccine. They’re all genetically similar, having come from a narrow breeding pool, which weakens their immune systems. And they likely share many of the features that have made the disease so deadly to minks.
“We don’t have direct evidence that black-footed ferrets are susceptible to COVID-19, but given their close relationship to minks, we wouldn’t want to find out,” Rocke said.
Rocke began working on the experimental vaccine in the spring, as she and Pete Gober, black-footed ferret recovery coordinator for the U.S. Fish and Wildlife Service, watched reports about the new coronavirus with growing alarm. An exotic disease is “the biggest nemesis for ferret recovery,” said Gober, who has worked with black-footed ferrets for 30 years. “It can knock you right back down to zero.”