Just as scientists are rapidly learning how SARS-CoV-2 affects humans, they are also quickly working to understand how it affects other animals. House cats, tigers, golden hamsters, and rhesus monkeys are all susceptible to SARS-CoV-2 infection. And while avian species such as duck and chicken are not, dogs, pigs, and ferrets have shown intermediate susceptibility.
The critical entry point for the virus into our cells is a protein called ACE2, which bonds with the spike protein of SARS-CoV-2. Animals and humans both expressing ACE2 in their cells, so scientists have been wondering why different species have different SARS-CoV-2 susceptibility, and if it is possible to predict which animals might be at risk.
In a preprint posted on bioRxiv in July, researchers at Vanderbilt University approached this question by comparing the amino acid sequence of ACE2 from different animal species. Amino acids are compounds that combine to form proteins. Inside cells, this amino acid chain folds into a three-dimensional shape. And as a result, some amino acids become hidden, and others exposed. Exposed ACE2 amino acids are of great interest because they determine whether SARS-CoV-2 can attach to the cell.
Using computer models, researchers identified amino acids in ACE2 that showed strong interactions with SARS-CoV-2. They observed that in non-susceptible animal species, these amino acids were often different, ultimately disrupting the attachment between the ACE2 protein and the spike protein of SARS-CoV-2. This allowed the researchers to make predictions about which animals species are possibly at risk of infection. They estimated that while horses and camels would be vulnerable to infection, cows, goats, and Malayan pangolins would present intermediate susceptibility.
In August, another preprint from researchers at Dalhousie University in Nova Scotia examined whether marine wildlife are susceptible to the virus. Using similar modeling methods, these researchers concluded that whales, dolphins, seals, and otters would be susceptible to SARS-CoV-2. They suggest that exposure could happen through contaminated sewage entering the sea.