When COVID-19 sits on people's laps: A systematic review of SARS-CoV-2 infection prevalence in household dogs and cats

Abstract

During the COVID-19 pandemic, questions were raised about whether SARS-CoV-2 can infect pets and the potential risks posed to and by their human owners. We performed a systematic review of studies on SARS-CoV-2 infection prevalence in naturally infected household dogs and cats conducted worldwide and published before January 2022. Data on SARS-CoV-2 infection prevalence, as determined by either molecular or serological methods, and accompanying information, were summarized. Screening studies targeting the general dog or cat populations were differentiated from those targeting households with known COVID-19-positive people. Studies focusing on stray, sheltered or working animals were excluded. In total, 17 studies were included in this review. Fourteen studies investigated cats, 13 investigated dogs, and 10 investigated both. Five studies reported molecular prevalence, 16 reported seroprevalence, and four reported both. All but two studies started and ended in 2020. Studies were conducted in eight European countries (Italy, France, Spain, Croatia, Germany, the Netherlands, UK, Poland), three Asian countries (Iran, Japan, China) and the USA. Both molecular and serological prevalence in the general pet population were usually below 5%, but exceeded 10% when COVID-19 positive people were known to be present in the household. A meta-analysis provided pooled seroprevalence estimates in the general pet population: 2.75% (95% Confidence Interval [CI]: 1.56-4.79%) and 0.82% (95% CI: 0.26-2.54%) for cats and dogs, respectively. This review highlighted the need for a better understanding of the possible epizootic implications of the COVID-19 pandemic, as well as the need for global standards for SARS-CoV-2 detection in pets.

Keywords: COVID-19; Pets; Prevalence; SARS-CoV-2; Transmission.

Fig. 1

Flow chart of the literature search and study selection process based on the PRISMA 2020 Standard for Systematic Reviews.

Fig. 2

Molecular and serological prevalence estimates for SARS-CoV-2 in household cats with and without known COVID-19 positive owners from the different countries and sampling periods. Each point is positioned in the middle of the respective sampling period (y-axis) and assigned to a different color depending on the country of the study, showing the prevalence of SARS-CoV-2 infection (x-axis) among cats from each study as summarized in Table 2, Table 3. The whiskers around each point indicate the 95% CIs. The dotted line refers to the sampling period of the data in question. Text annotations per point are the reference of the studies. The upper category (’PCR’ and’Serology’) indicates the detection method, molecular or serological, respectively. The right axis indicates the study of cats with known (conditionally selected) COVID-19 positive owners (Table 2) and the study of cats without known COVID-19 positive owners (Table 3).

Fig. 3

Molecular and serological prevalence estimates for SARS-CoV-2 in household dogs with and without known COVID-19 positive owners from the different countries and sampling periods. Each point is positioned in the middle of the respective sampling period (y-axis) and assigned to a different color depending on the country of the study, showing the prevalence of SARS-CoV-2 infection (x-axis) among cats from each study as summarized in Table 2, Table 3. The whiskers around each point indicate the 95% CIs. The dotted line refers to the sampling period of the data in question. Text annotations per point are the reference of the studies. The upper category (’PCR’ and’Serology’) indicates the detection method, molecular or serological, respectively. The right axis indicates the study of cats with known (conditionally selected) COVID-19 positive owners (Table 2) and the study of cats without known COVID-19 positive owners (Table 3).