Nationwide seroprevalence of SARS-CoV-2 Delta variant and five Omicron sublineages in companion cats and dogs in the USA: insights into their role in COVID-19 epidemiology.

Understanding SARS-CoV-2 epidemiology in companion animals is critical for evaluating their role in viral transmission and their potential as sentinels for human infections. This large-scale serosurvey analyzed serum samples from 706 cats and 2,396 dogs collected across the USA in 2023 using a surrogate virus neutralization test (sVNT) to detect SARS-CoV-2 antibodies. Overall, 5.7% of cats and 4.7% of dogs tested positive for antibodies, with younger animals (under 12 months) showing significantly lower seropositivity rates (= 0.0048). Additionally, we analyzed 153 positive samples for variant-specific antibody responses using six sVNT kits targeting the Delta variant and five Omicron sublineages. Among cats, 67.5% showed antibodies to Delta, with positivity rates for Omicron sublineages as follows: BA.1 (62.5%), BA.2 (42.5%), BA.4/BA.5 (77.5%), XBB (52.5%), and XBB.1.5 (45.0%). In dogs, 55.8% were positive for Delta, and Omicron sublineage rates were BA.1 (46.0%), BA.4/BA.5 (37.2%), XBB (58.4%), BA.2 (13.3%), and XBB.1.5 (9.7%). Given the close contact between companion animals and humans, and the persistence of antibodies against various SARS-CoV-2 variants and sublineages, our findings suggest that seroprevalence in cats and dogs may serve as valuable tool for tracking COVID-19 epidemiology.