We conducted a case-control study with patients that sought medical care with COVID-19 symptoms. They were asked wether they owned pet cats and/or dogs to evaluate the exposition to SARS-CoV-2 and the associated risk of having a pet in their residences.
From 8th March to 31st November 2021, patients with flu-like/respiratory syndrome symptoms seeking medical care at a primary healthcare center in Cidade Estrutural (city nearby Brasilia, Distrito Federal, Brazil) were invited to participate in our study about COVID-19 incidence. All patients agreeing to participate signed consent instruments, were interviewed, and had nasopharyngeal samples collected using a swab for SARS-CoV-2 detection by RT-qPCR. The survey included questions about socio-demographic descriptors and the presence of pets in their residences.
RT-qPCR assays were performed with SARS-CoV-2 RNA isolated from nasopharyngeal swab samples. Nucleic acid extraction was conducted with the EXTRACTA 32 kit (MVXA-P016 FAST) in a Loccus automated extractor following manufacturer’s instructions. SARS-CoV-2 was detected by the RT-qPCR Allplex™ 2019-nCoV Assay (Seegene Inc.) for the amplification of genes E, RdRP and N, as well as an internal control gene, according to the manufacturer's protocol. RT-qPCR results were considered positive (SARS-CoV-2 RNA detected) when the internal control and at least two genes were amplified, negative (SARS-CoV-2 RNA not detected) when the internal control and none or only one gene was amplified, and inconclusive when the internal control did not amplify. Inconclusive results were repeated one time.
The inclusion criteria were: 1) answering the question of whether there were any pets in their residences, and if they did, specified which kind, and 2) having a positive or negative result in the SARS-Cov-2 detection test. Those who did not meet these criteria were excluded.
Sample characteristics were described with descriptive statistics. Odds Ratio (and its respective 95% confidence interval) of having a pet dog/cat in relation to being SARS-CoV-2-positive in RT-qPCR were then calculated.
All procedures were conducted in accordance with the ethical standards for research with human participants following the recommendations of the institutional and national research committees, and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Research Ethics Committee of the Faculty of Medicine at University of Brasília (CEP-FM/UnB, CAAE 39892420.7.1001.5558; CAAE 40557020.6.3001.5553) and Fundação de Ensino e Pesquisa em Ciências da Saúde (FEPECS/SES/DF, CAAE 40557020.6.3001.5553).