Since the start of the pandemic, SARS-CoV-2 has been reported to infect, and be transmitted by, several animals other than humans. Most notably, the transmission of the virus between keepers and tigers and lions in the Bronx Zoo in New York City. However, to date, the full range of animal species that are susceptible to SARS-CoV-2 infection remains unclear.

Instead of infecting a large variety of animal species with SARS-CoV-2 to measure susceptibility, researchers at the University of Bern and at the Institute of Virology and Immunology (IVI) used their repository of well-differentiated airway epithelial cell (AEC) cultures from various domesticated and wildlife animal species to assess their susceptibility to SARS-CoV-2. The team observed that SARS-CoV-2 replicated efficiently only in monkey and cat AEC culture models. These findings, taken together with previous reports of human-to-animal spillover events, “warrant close surveillance to determine the potential role of cats, monkeys, and closely related species as spillback reservoirs for SARS-CoV-2,” the authors noted.

This work is published in Emerging Infectious Diseases, in the paper, “Susceptibility of Well-Differentiated Airway Epithelial Cell Cultures from Domestic and Wild Animals to Severe Acute Respiratory Syndrome Coronavirus 2.

The team created a large collection of cell cultures from various domesticated and wildlife animal species. To do this, they isolated AEC from tracheobronchial tissue from deceased animals and created a cell biobank from different animal species that can be used to establish well-differentiated AEC culture models for SARS-CoV-2. To date, the cell biobank contains primary cells from 12 different animal species: rhesus macaque, cat, ferret, dog, rabbit, pig, cattle, goat, llama, camel, and two neotropical bat species.

Ronald Dijkman, PhD, Institute for Infectious Diseases (IFIK), University of Bern [Courtesy of Ronald Dijkman]
“Our collection is unique, and thus far we are the first that have used such a large collection of advanced in vitro cell culture models from various domesticated and wildlife animal species to assess their susceptibility to SARS-CoV-2 infection,” said Ronald Dijkman, PhD, group leader in experimental virology at the Institute for Infectious Diseases (IFIK), University of Bern.

The researchers found that the in vitro results agreed well with previously published studies using animal experimentation to assess the susceptibility of different animals to SARS-CoV-2 infection. Using whole viral genome sequencing, the researchers also observed that SARS-CoV-2 replicated in the in vitro models of monkey and cats, without the need for the virus to adapt. These findings suggest that certain species of monkeys and cats may be particularly vulnerable to SARS-CoV-2 infection. “Our findings, together with the reports from previously documented spillover events, indicate that close surveillance of these animals and other close relatives, whether they live in the wild, captivity, or households, is necessary,” said Dijkman.

SARS-CoV-2 infected airway epithelial cell (AEC) cultures from diverse mammalian species. Only AEC cultures from rhesus macaques and cats show the presence of SARS-CoV-2 infected cells (green). [IFIK/UniBE]
This information can be used for SARS-CoV-2 surveillance at the human-animal interface. Specifically, it helps authorities establish and tailor early detection surveillance programs to monitor animals that can act as potential spillback reservoirs for SARS-CoV-2. Dijkman added, “This will benefit the general public since it will help prevent new SARS-CoV-2 variants from developing in animal reservoirs and potentially being reintroduced into the human population, to which the current vaccines may not be protective.”