Blackfooted ferrets (Mustela nigripes), are losing their homes to human development on the Great Plains. The highly endangered member of the weasel family (Mustelidae) were innoculated by scientists for another disease--COVID-19--this summer. The reason for the special treatment is that the Department of Agriculture is seeking a veterinary vaccine for minks, which are raised commercially for their fur. Europe has had to cull millions of minks after humans transmitted the disease to them. Danish health officials found 200 cases of human infections that could be genetically traced to farm raised minks. Thousands of minks have died on Utah farms. The US produces about three million mink pelts a year.
Ferrets were saved from the brink of extinction decades ago, but have faced an uphill battle since then. Their gene pool is small making them vulnerable to disease, and their favorite prey animal, the prairie dog, is facing extermination from grazing, agriculture and human settlement. The trial vaccination of 120 ferrets living in the Ferret Conservation Center near Ft. Collins, CO was not totally altruistic. The possibility of zoonotic transmission exists, but is highly unlikely given that humans do not handle blackfooted ferrets in the wild as they do farmed animals. It is however, closely related to the mink.
The ferret was declared extinct in the wild in 1979. An isolated population was found still living on a ranch Wyoming. Most of the colony had died of sylvatic plague, a form of the Black Death which wiped out human populations in the past. Scientists rescued eighteen of the animals to start a captive breeding program, the usual last resort for saving a species going extinct. A vaccine for the plague in ferrets was developed using a purified protein from the Yersinia pestis bacterium.
Researchers began to develop a COVID-19 vaccine using the same technique, in this case a purified spike protein from the SARS CoV-2 virus. The first doses were given to eighteen, young male ferrets who were observed for an immune response. Within weeks of a second shot, animals showed increased levels of antibodies in their blood--a positive sign. By early fall, 120 of 180 resident ferrets were inoculated. So far the vaccine appears to be safe, but efficacy has not yet been proven. That will take a well designed blind study to decide the issue. The approach used--an inactivated protein from the pathogen to stimulate an immune response--is a successful one that has led to vaccines for polio and influenza. Thank you, ferrets.