A recent survey conducted by a team of scientists from France reveals that pets living with confirmed coronavirus disease 2019 (COVID-19) patients have a high prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. The study is currently available on the bioRxiv* preprint server.
Since the emergence of the COVID-19 pandemic, the majority of studies have indicated that there is only human to human transmission of SARS-CoV-2 via respiratory droplets. Although no definitive evidence is there yet to support the zoonotic transmission of SARS-CoV-2, previous studies have shown that household dogs and cats are susceptible to other alpha- and beta-coronaviruses. Moreover, epidemiological and biological characteristics of coronaviruses suggest that there are possibilities of pathogen spillover. Given these observations, it is crucial to understand if pets are susceptible to catch the infection from their SARS-CoV-2 positive owners.
High prevalence of SARS-CoV-2 antibodies in pets from COVID-19+ households. Image Credit: Chaay_Tee / Shutterstock
Current study design
In the current study, the scientists conducted a serological survey between May 2020 and June 2020 on pets living with SARS-CoV-2 positive patients. The survey was conducted in two regions of eastern France with similar epidemiological status and healthcare policies.
The scientists created three experimental groups. 1. A COVID-19 positive household group with pets (dogs and cats) who were living with at least one SARS-CoV-2 positive. 2. Symptomatic patients; the unknown status household group included pets living with owners of unknown status. 3. The control group, including pets that were sampled before the COVID-19 pandemic. To exclude the possibility of antibody cross-reactivity, they included serum samples of ten cats with feline infectious peritonitis virus infection.
They conducted three different antibody detection tests using serum samples collected from the pets. The results revealed the presence of SARS-CoV-2 immunoglobulin G molecules (IgGs) against the nucleocapsid (N) protein and S1 and S2 subunits of the spike (S) protein. Moreover, SARS-CoV-2-specific neutralizing antibodies were detected using a retrovirus-based pseudoparticle assay. The pets having positive results in sero-neutralization assay or in all three antibody detection assays were considered SARS-CoV-2 seropositive. Since none of the pets in the control group showed seropositive status in antibody detection assays or sero-neutralization assay, the scientists believed that the positivity criteria they followed in the study ensured 100% specificity.
Of 47 pets tested in the COVID-19 positive household group, 10 displayed the presence of anti-SARS-CoV-2 antibodies (21%). However, there was no significant difference in seropositivity between dogs and cats. In the unknown status household group, a total of 38 pets were tested, of which only one had antibodies against SARS-CoV-2. This indicates that the seroprevalence of SARS-CoV-2 antibodies is significantly higher in COVID-19 positive households than in unknown status households. Moreover, the scientists analyzed that the risk of having SARS-CoV-2 infection was eight times higher in pets living with confirmed COVID-19 patients than those living with owners of unknown status.
Because anti-N antibody tests are known to provide underestimated information about SARS-CoV-2 seropositivity than anti-S antibody tests in the general population, the scientists believed that the actual percentage of seropositive pets in the current study would have been 53%, as estimated from the anti-S antibody test results.
The significantly high prevalence of anti- SARS-CoV-2 antibodies in pets living with COVID-19 patients indicates that the pets might have got the infection from their owners. However, the study cannot give a definitive answer on whether seropositive pets were actually infected with SARS-CoV-2.
Considering that pets are infected with SARS-CoV-2, the current study findings generate an open question if animals can contribute to the COVID-19 pandemic because of animal-to-human pathogen spillover. The study also emphasizes that people living in close contact with animals should take necessary precautions to contain possible zoonotic transmission of SARS-CoV-2.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.