Abstract
In the present study, the course of SARS-CoV-2 natural infection in two asymptomatic cats is investigated. The source of the virus for the cats was their COVID-19-affected owner, with whom they were in continuous proximity, in a small household setting. Oropharyngeal and fecal swabs were collected to investigate the course of SARS-CoV-2 RNA concentrations, as well as the directionality of the chain of virus transmission. Both infected cats were real-time RT-PCR-positive on various time-points. Pharyngeal shedding of at least 6 days was observed in both cats, with high SARS-CoV-2 titers (> 7 Log10 copies/swab) on the first sampling time-point. In one cat, after the initial decline, slightly increasing virus titers were measured 3-to-6 days after the first real-time RT-PCR-positive swab. Serological testing of this cat revealed absence of seroconversion. The course of viral RNA concentrations in the fecal swabs of the other cat was similar to that in its pharynx. The detected SARS-CoV-2 strains, from both infected cats and their owner, underwent whole genome sequencing, revealing the absence of emergence of cross-species adaptive mutations in cats. Our results support the notion that human SARS-CoV-2 strains are relatively well-adapted to cats. It is still unclear whether asymptomatic animals could play a role in COVID-19 epidemiology, in case of interaction with naïve animals and/or people. The findings of the present study highlight difficulties in SARS-CoV-2 transmission to cats, as neither the two infected cats nor their owner were able to transmit the virus to a third cat living in the same small flat, despite their very close contact during the days corresponding to high virus shedding.