Study population and setting
To evaluate thee susceptibility of several wildlife species to SARS-CoV-2, animals of nine species were captured in three counties of northern Colorado, USA or were purchased from a private vendor: deer mice (Peromyscus maniculatus, n = 9), house mice (Mus musculus, n = 6), bushy-tailed woodrats (Neotoma cinerea, n = 6), Wyoming ground squirrels (Urocitellus elegans, n = 2), black-tailed prairie dogs (Cynomys ludovicianus, n = 9), fox squirrels (Sciurus niger, n = 3), cottontail rabbits (Sylvilagus sp., n = 3), striped skunks (Mephitis mephitis, n = 6), and raccoons (Procyon lotor, n = 3). Animals were inoculated intranasally with between 10^4.5 and 10^4.9 plaque forming units (PFU) of SARS-CoV-2. All species had 1-3 inoculated individuals that were sacrificied at 3 days post-infection (DPI) to assess viral shedding and pathology. Select species (deer mice, house mice, woodrats, prairie dogs, raccoons, skunks) had additional inoculated individuals sacrificed at DPI 7 and 28; serum was collected from animals at DPI 28 to test for neutralizing antibodies against SARS-CoV-2.
Summary of Main Findings
None of the species showed clinical signs of infection, including normal body temperatures measured in skunks and raccoons, and no gross lesions were found in any animals at the time of necropsy. Deer mice, bushy-tailed woodrats, and striped skunks were susceptible to SARS-CoV-2, shedding infectious virus orally for up to DPI 3 or 4. Virus was isolated from tissues collected from the upper respiratory tract and lungs; all three species showed mild pathology in necropsied lung tissues. Cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice, and raccoons were not susceptible to virus infection. Inoculated deer mice, woodrats, and skunks sacrificed at DPI 28 had neutralizing antibodies against SARS-CoV-2, while house mice, prairie dogs, and raccoons did not.
The study confirmed that all animals were seronegative for SARS-CoV-2 prior to inoculation. The presence of infectious virus shedding in inoculated animals (not just viral RNA) was tested using cell culture; results were confirmed via PCR on material collected from positive cell cultures.
The high dose given to animals may not be representative of natural infections. The limited number of animals collected from one regional population may not be generalizable across the entire range of each species. Additionally, the methods did not evaluate the ability of inoculated animals to transmit the virus to naïve contacts. Thus, this experiment can only indicate that infection of peridomestic rodents and skunks may be possible. Finally, the authors did not test for the presence of other coronaviruses in animals that may have affected results, e.g., cross-reactivity of antibodies.
Humans may interact directly with peridomestic wildlife living nearby or inside human dwellings, or indirectly through their pets (e.g., cats hunting rodents, dogs and raccoons scavenging trash). Thus, there is concern that SARS-CoV-2 could be spread to wildlife and eventually establish ongoing transmission that could result in new zoonotic spillover of SARS-CoV-2. Previous analyses of the ACE2 receptor that binds to SARS-CoV-2 suggested that many carnivore and rodent species may be susceptible. These results confirm previous studies showing that deer mice were susceptible to infection and that house mice are not susceptible; the study represents the first experimental evaluation of susceptibility in seven other species.
This review was posted on: 12 February 2021