Human ELISA Detects anti-SARS-CoV-2 Antibodies in Cats: Seroprevalence and Risk Factors for Virus Spread in Domestic and Stray Cats in Bulgaria

Abstract

The aim of this study was to verify whether the human DR-ELISA for the detection of anti-SARS-CoV-2 antibodies can be applied in cats, and to assess the risk factors that determine the spread of the virus among the cat population in Bulgaria. The study included 92 serum samples collected from 68 domestic and 24 stray cats aged from 3 months to 20 years of age in the period of January–June 2021. The samples originated from three regions in Bulgaria and from three places of inhabitance. DR-ELISA based on peroxidase-labeled SARS-CoV-2 N protein was employed to detect IgA, IgG and IgM antibodies in the samples. Subsequently, the results were compared with a commercially available multi-species ELISA kit. There was high seroprevalence (83.33%) in stray cats and 41.18% in domestic cats, confirmed by the human and veterinary ELISA kit. The positive cases in the regional cities were 42.86%, in small towns 50% and in villages 78.26%. Cats under 7 years had a five times higher risk than those over 7 years (p = 0.001). The risk was seven times higher for stray cats than for domestic cats (p = 0.001). In addition, the results indicate that the risk was the highest for cats in villages (p = 0.006) compared to cats in other places of inhabitance. This study demonstrates that human DR-ELISA may be successfully applied to monitor the circulation of SARS-CoV-2 in cats and other susceptible species. Cats might serve as sentinel animals for tracking the virus in nature and in inhabited areas (strays) and to discover asymptomatic cases in humans/owners.

SARS-CoV-2 Infection and Clinical Signs in Cats and Dogs from Confirmed Positive Households in Germany

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Retrospective Analysis of the Spread of SARS-CoV-2 in the Mediterranean Part of Bulgaria, During the First Wave of the Pandemic

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“…20,21 An important part of controlling the spread of respiratory viruses is the availability of reliable diagnostic assays. The serological diagnosis of SARS-CoV-2 utilizes assays with different characteristics (antibody types and quantity), based on various principles, such as quick antigen tests based on nanoparticles, 29,30 qualitative and quantitative ELISA, immunofluorescence, [31][32][33] electrochemiluminescence assay 34 and automated systems. 35,36 Different serological tests also have different informativeness depending on the team and the combination of antibodies they prove.…”

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“…Our previous study validated and applied nested (n) One-Step RT PCR for SARS-CoV-2 detection in swab samples [ 51 ] and sera from cats [ 52 ]. The assay showed high sensitivity, as it was able to detect low concentrations of virus RNA.…”