Covid-19 and dogs : seroprevalence in dogs in Sweden, concerns among their owners and development of the method COVID-19 SIA

Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the third coronavirus to cause an epidemic or pandemic in the 21st century. In the beginning of January 2021 almost 88 million cases of covid-19 have been reported to World Health Organization (WHO) and more than 1.8 million people have died. The world is currently waiting for a vaccine and in the meantime, scientists worldwide continue to investigate the features of the virus. According to current literature it seems improbable that dogs would serve as reservoirs, but cats and other felines might be possible intermediate hosts, as well as minks. In this project a serological method called COVID-19 Suspension Immunoassay (SIA), earlier used for both humans and animals, was further developed to study the prevalence of SARS-CoV-2 antibodies in dogs. In total, 443 dogs from five municipalities participated in the study and donated blood. Eighty-three (18.7%) of them lived with owners who also participated in a survey study. The dogs were divided into two groups, group A for dogs with completed owners’ questionnaires and group B for anonymous blood donors. Since the method had never been used for this purpose before, the limit for positive results was not determined when the project started. Depending on where the cut-off was set, results differed from 12 to 16 antibody positive samples. A preliminary cut-off point of 300 median fluorescence intensity (MFI) was determined, resulting in a study prevalence of 2.7%. The purpose of the survey performed in group A was to investigate whether there might be a higher probability for dogs to have SARS-CoV-2 antibodies if they lived with owners who were seropositive and how closely the dogs lived with their owners. The questionnaires also addressed concerns among the dog owners, if they worried about covid-19 regarding themselves, their friends and families, the society, and their pets. Results showed that there was an indication but not a statistically significant higher probability for the dogs to develop antibodies if they lived with owners who had been confirmed with covid-19. All seropositive dogs lived close or very close with their owners. The results indicated that owners in general worried more about their friends, family, and the society than for themselves. Concerns about their pets getting sick from covid-19 were very small. Further studies with a greater quantity of data would give more reliable results for the cut-off point and consequently also for the seroprevalence and the probability of dogs developing antibodies if their owners have been confirmed with covid-19.