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.