Dr. Matthew Cronin

COVID-19 is everywhere, and the virus causing the disease (SARS-CoV-2) has even been found in wild animals. COVID-19 has been found in white-tailed deer in several states and provinces, including Ohio, Iowa, Illinois, Michigan, Pennsylvania, New York, Oklahoma, Texas and Quebec, Canada. The USDA National Wildlife Research Center in Fort Collins, CO, and state wildlife agencies are testing for COVID-19 in other states.

It is thought that COVID-19 was transmitted from humans to deer. As of now, there is no record of COVID-19 being transmitted from deer or other wild animals to humans, but COVID-19 has been transmitted from captive animals to humans.

Research on COVID-19 in white-tailed deer was published in the Journal of Virology in 2021. The researchers did an experiment at an indoor facility in Iowa, in which four captive deer were inoculated by spraying the COVID-19 virus into their noses.

Two additional deer were not inoculated but were kept in the same room, separated from the inoculated deer by a 3-foot Plexiglass barrier to prevent physical contact. There was air flow between the areas with the inoculated deer and the uninoculated deer. At the end of the experiment, all six deer were infected with COVID-19 and produced antibodies to it.

Additional research published in the journal Nature in 2021 reported COVID-19 in wild deer. The researchers took nasal swabs from 360 deer killed in a population management program in northeast Ohio and did mRNA COVID tests on them. About 36 percent of the deer were infected in six of the nine locations that were sampled. Males and heavier deer were more likely to have a positive COVID test than other deer.

Although research shows that deer are susceptible to infection, it is believed they don’t show symptoms, or they have mild symptoms such as a cough or raspy breathing.

COVID-19 has also been found in other wildlife. Captive mink in Dutch farms contracted COVID from humans and then transmitted it back to humans. Mink in farms in Denmark and Poland also have had COVID-19. Pet dogs, cats, ferrets and zoo animals, including big cats (e.g., tigers), coatimundis, otters, primates and hyenas have also had COVID-19. USDA is testing for COVID-19 in other species in the wild, such as coyotes, skunks and raccoons.

The Centers for Disease Control and Prevention has recommendations to reduce potential transmission of COVID-19 from wildlife to humans, such as keeping people and pets a safe distance from wildlife. Hunters should be cautious when field dressing and processing harvested deer and should wear gloves and masks and wash hands. Eating thoroughly cooked deer meat is thought to be safe.

Humans transmitting COVID-19 to deer might seem unlikely considering the social distancing guidance of 6 feet to minimize the spread of the disease among people. Hunters, even bowhunters, know it’s hard to get within 6 feet of a deer.

The researchers who studied COVID-19 in deer suggest that deer in urban and suburban areas may be exposed to COVID-19 in trash, backyard feeders, bait stations, wildlife hospitals and infected water sources. Perhaps gardens with plants attractive to deer and pet feces also contribute. High population density of deer might facilitate deer-to-deer transmission of COVID-19, as with other diseases such as chronic wasting disease and Lyme disease.

COVID-19 in wildlife is a concern, but the potential for COVID-19 infecting livestock is perhaps a greater concern. Research indicates that pigs and poultry are not susceptible. Experimental infection of cattle with COVID-19 in two studies indicates that cattle show low susceptibility to SARS-CoV-2 infection, no productive infection or replication of COVID-19, and no cattle-to-cattle transmission.

These two experiments involved direct infection into the nose, trachea or blood with one strain (i.e., variant) of the virus in each of the studies, and they show that cattle are likely not susceptible to COVID-19. New COVID-19 variants and interactions with related viruses suggest that more research of COVID-19 in cattle is warranted.

An interesting observation is that Ivermectin has been effective in treating COVID-19 in humans in India. Ivermectin is commonly used in livestock and perhaps could be useful for treatment if COVID-19 does occur in livestock. — Dr. Matthew Cronin

(Matthew Cronin was a research professor at the University of Alaska, a U.S. Coast Guard officer and is now at Northwest Biology Company LLC in Bozeman MT)