Can cats become infected with Covid‐19?
Xiangdong Li
Abstract
In a recent letter, Angel Almendros (VR, 4/11 April 2020, vol 186, pp 419-420) summarised the sporadic reports about the Covid-19 infections of two dogs (both in Hong Kong) and two cats (one in Hong Kong and another in Belgium). Although the positive results were confirmed by serological tests or RT-PCR and gene sequencing, the virus was not successfully isolated. The evidence is accumulating and building on almost a daily basis, but here I summarise what we know so far from researchers working on the risk to cats from SARS-CoV-2. After publication of the letter from Almendros, Shi and colleagues reported an experimental infection using two SARS-CoV-2 viruses (one isolated from the environment and one from a human patient with Covid-19) of a number of companion and domestic animals. They found that ferrets and cats, but not dogs, are highly susceptible to Covid-19.1 The experimentally infected juvenile cats (aged 70 days to three months) showed severe histological lesions in the nasal and tracheal mucosal epitheliums and lungs. Some cats died before euthanasia on day 3 after infection, but the authors did not describe the clinical signs in these cats. A naturally infected cat (transmitted by its Covid-19-positive owner) showed severe clinical signs including diarrhoea, vomiting and breathing difficulties.2 Results provide evidence that people might transmit SARS-CoV-2 to cats On 3 April 2020, Zhang and colleagues performed a retrospective serological investigation on the cats in Wuhan city, the epicentre of the Covid-19 epidemic.3 They found 15 of 102 cat sera collected after the outbreak were positive using an in-house indirect ELISA. Among these serologically positive cats, three that were strongly positive on the ELISA also showed high virus neutralising antibody titres ranging from 1/360 to 1/1080. The owners of these three cats have been confirmed as Covid-19 positive (the other ELISA-positive cats were six stray cats and six from pet hospitals). These results provide evidence that people might transmit SARS-CoV-2 to cats. It is confirmed that SARS-CoV-2 can be transmitted between cats via respiratory droplets and from people to cats, but it remains unknown if the reverse transmission from cats to people can occur. In the same study, it was reported that 39 cat serum samples taken before the Covid-19 outbreak were serologically negative,3 which suggested cats may not transmit the virus to people. The role cats play in this Covid-19 pandemic should be further explored. However, we should never abandon our family pets.