A team of scientists at the University of Glasgow has identified two known cases of human-to-cat COVID-19 transmission in the UK.

In the study, led by the University of Glasgow and published today in the Veterinary Record, researchers describe two cases of human-to-cat SARS-CoV-2 transmission, found as part of a COVID-19 screening programme of the feline population in the UK.

The cats, both different breeds, came from two separate households and displayed mild to severe respiratory signs. Researchers from the MRC-University of Glasgow Centre for Virus Research (CVR) in partnership with the Veterinary Diagnostic Service of the University’s School of Veterinary Medicine, believe both cats were infected by their owners, who were also displaying COVID-19 symptoms prior to the cats becoming unwell.

The first cat 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, although 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. The cat 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 APHA.

Researchers at the CVR completed full genome sequencing of the SARS-CoV-2 genome in cat 2 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 2’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.

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.”

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 cats, ferrets and hamsters are susceptible.

This study was funded by Wellcome ISSF COVID Response Fund and supported by the Medical Research Council (MRC).