The recent SARS-CoV-2 pandemic has led to several thousand deaths and millions of cases in Sweden. It has on several occasions been proven that animals can also be infected by SARS-CoV-2, though they rarely have symptoms. Therefore, they may act as silent hosts to the virus, transmitting it further to humans and other animals. This is a possible problem when pets visit the veterinarian or places where animals co-mingle. This study aimed to investigate how common SARS-CoV-2 infection was in Swedish cats and dogs.
This was done with real-time Quantitative reverse transcriptase PCR and Enzyme Linked ImmunoSorbent Assay, to determine how common both current and past infections are, and how many animals develop antibodies. Samples have been sent to the Swedish National Veterinary Institute for routine analysis. RNA was previously extracted and stored at -70 °C, and serum was stored at -20 °C.
Nearly 3 % of samples were positive for antibodies, meaning the animals had a SARS-CoV-2 infection at some point. Only three samples out of 1 969 were positive with real-time quantitative reverse transcriptase PCR, all three samples from cats. The reason for this is most probably a small window where samples can be taken and be positive, and that animals do not shed a lot of the virus once infected. This means that it is unlikely that companion animals are a major contributing factor to the spread of SARS-CoV-2 and the continuation of the pandemic.