Occurrence of Spike Antigen Specific SARS-CoV-2 Antibodies in Pre-Pandemic Samples of Domestic Cats Raises New Questions

ABSTRACT

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome of coronavirus SARS-CoV-2. Former studies showed the high similarity of SARS-CoV-2 to coronavirus (RaTG13) isolated from intermediate horseshoe bat and that the bats, ferrets, domestic cats were capable of transmitting the virus to contact conspecifics, which supports the virus circulation. We estimated the occurrence of antibodies to SARS-CoV-2 in domestic cats after the outbreak in Moscow and corresponded it with earlier data. Among the domestic cats of Moscow sampled in 2020 10% were positive for IgG against RBD antigen of SARS-CoV-2, however, five cats (of 172;2.9%) from Moscow 2018 were IgG-positive for RBD peptide of SARS CoV-2. There were no positive domestic cats sampled in the Russian Far East. The antibodies to SARS-CoV-2 were not detected in archive human samples from Moscow. These results forced us to suggest either the exposure of cats to SARS-CoV-2 in Moscow in 2018 which is highly unlikely, or the effect of other viral peptides on the false-positive results. All in all, these proteins were found only in cats in one region of Russia and were not related to the feline coronavirus.