SARS-CoV-2 in Animal Companions: A Serosurvey in Three Regions of Southern Italy

Several animal species have been found to be susceptible to SARS-CoV-2 infection. The occurrence of infection in dogs and cats living in close contact with owners deserves particular attention from public health authorities in a One Health approach. In this study, we conducted serological screening to identify SARS-CoV-2 exposure in the sera from dogs and cats in three regions of southern Italy sampled during the years 2021 and 2022. We collected 100 serum samples in 2021 (89 from dogs and 11 from cats) and 640 in 2022 (577 from dogs and 63 from cats). Overall, the ELISA positivity rate was found to be 2.7% (20/740), with higher seroprevalence in dogs. Serum neutralization tests confirmed positivity only in two samples collected from dogs, and the assays, performed with serologically distinct SARS-CoV-2 variants, showed variant-specific positivity. This paper shows that monitoring SARS-CoV-2 exposure in animals might be affected by the viral antigenic evolution, which requires continuous updates to the serological tests used. Serological surveys are useful in understanding the true extent of exposure occurring in specific animal populations, not suffering the same limitations as molecular tests, and could help in identifying the infecting virus if tests able to characterize the immune response are used. The use of variant-specific validated serological methods should always be considered in serosurvey studies in order to determine the real impact of emerging variants on animal populations and its implications for veterinary and human health, as well as to identify potential reservoirs of the virus and its evolutionary changes.

A longitudinal observational study in two cats naturally-infected with hepadnavirus

Hepatitis B virus (HBV) is a major cause of liver disease in humans including chronic hepatitis and hepatocellular carcinoma. Domestic cat hepadnavirus (DCH), a novel HBV-like hepadnavirus, was identified in domestic cats in 2018. From 6.5 %-10.8 % of pet cats are viremic for DCH and altered serological markers suggestive of liver damage have been identified in 50 % of DCH-infected cats. DCH DNA has been detected in association with characteristic lesions of chronic hepatitis and with hepatocellular carcinoma in cats, suggesting a possible association. In this study longitudinal molecular screening of cats infected with DCH was performed to determine if DCH can cause chronic infections in cats. Upon re-testing of sera from five DCH-positive animals, 2-10 months after the initial diagnosis, three cats tested negative for DCH on two consecutive occasions using quantitative PCR. Two other cats remained DCH-positive, including an 8-month-old female cat re-tested four months after the initial positive result, and a 9-year-old male cat, which tested positive for DCH on six occasions over an 11-month period. The latter had a history of chronic hepatopathy with jaundice, lethargy and elevated serum alanine transaminase levels (ALT). During the period of observation, DCH titers ranged between 1.64 × 10⁵ and 2.09 × 10⁶ DNA copies/mL and ALT was persistently elevated, suggesting chronic infection. DCH DNA was not detected in oral, conjunctival, preputial and rectal swabs from the two animals collected at several time points. Long-term (chronic) infection would be consistent with the relatively high number of viremic cats identified in epidemiological investigations, with the possible association of DCH with chronic hepatic pathologies and with what described with HBV in human patients.