A team of scientists has identified two known cases of human-to-cat Covid-19 transmission in the UK.
The study, led by the University of Glasgow and published in the Veterinary Record, carried out a coronavirus screening programme of the feline population in the UK.
It found that human-to-cat SARS-CoV-2 transmission had occurred in two cases from different households and among different breeds of cat.
Researchers said the people were displaying mild symptoms before passing it onto their pets who displayed mild to severe respiratory signs.
However there has been no evidence to suggest the transmission can work the other way round where humans can catch it from cats.
Professor Margaret Hosie from the MRC-University of Glasgow Centre for Virus Research, lead author of the study, said: "These two cases of human-to-animal transmission, found in the feline population in the UK, demonstrate why it is important that we improve our understanding of animal SARS-CoV-2 infection.
"Currently animal-to-human transmission represents a relatively low risk to public health in areas where human-to-human transmission remains high.
"However as human cases decrease the prospect of transmission among animals becomes increasingly important as a potential source of SARS-CoV-2 reintroduction to humans. It is therefore important to improve our understanding of whether exposed animals could play any role in transmission."
The first cat identified with Covid-19 was a four-month-old female Ragdoll kitten from a household in which the owner developed symptoms that were consistent with SARS-CoV-2 infection at the end of March 2020. However the owner was not tested.
The kitten was presented to its veterinary surgeon in April 2020 with difficulty breathing. Sadly the cat's condition deteriorated and it later had to be put down.
Post-mortem lung samples later revealed damage to the lungs consistent with a viral pneumonia and there was evidence of SARS-CoV-2 infection.
The second cat was a six-year-old female Siamese from a household where one owner tested positive for Covid-19. It was taken to the vet with nasal discharge and conjunctivitis but these clinical signs remained mild and the cat later recovered.
Covid-19 infection was demonstrated in the cat as part of a UK-wide Covid-19 feline screening programme and this was confirmed by the Animal and Plant Health Agency (APHA).
Researchers at the CVR completed full genome sequencing of the SARS-CoV-2 genome in cat two and found that it was very similar to viral genomes circulating in humans.
The researchers found no evidence of species adaptation in the cat's viral sequences and concluded that any mutations present in cat two's viral genome were likely also present in the owner’s virus, although the genome sequence from the owner was not available for comparison.
At present there is no evidence of cat-to-human transmission or that cats, dogs, or other domestic animals play any role in the epidemiology of human infections with SARS-CoV-2. Whether cats with Covid-19 could naturally transmit the virus to other animals, or back to humans, remains unknown.
However scientists believe these two known cases of human-to-cat transmission in the UK are likely to be an underestimate of the true frequency of human-to-animal transmission as animal testing is limited.
Since the pandemic began there have been reports of cats from Covid-19 households in Hong Kong, Belgium, the USA, France, Spain, Germany, Russia, Japan, Italy, Chile, Canada, Brazil, Argentina, Switzerland, and Latvia that tested positive for SARS-CoV-2 and were presumed to be infected from their owners.
Naturally occurring SARS-CoV-2 infections have been reported in cats, non-domestic cats, and dogs. Scientists have also shown that ferrets and hamsters are susceptible.
