INTRODUCTION
The world is currently fighting an extremely small organism, SARS-CoV-2, the causative virus of the disease that has caused a global pandemic known as COVID-19. SARS-CoV-2, a member of the family Coronaviridae, is a single-stranded enveloped RNA virus. Coronaviruses (CoVs), such as SARS-CoV-2, can emerge from wildlife hosts and infect humans and domestic and/or livestock animals (Dhama et al., 2020; Shi et al., 2020; Hu et al., 2021). Thus, they can cause epidemic or pandemic outbreaks, with low, medium, or high morbidity and mortality. Sequence analyses suggest that SARS-CoV-2 could have originated from bat CoVs, highlighting interspecies transmission of CoVs (Boni et al., 2020; Guo et al., 2020; Guo et al., 2021), although the intermediate host is currently unknown.
Studying the zoonotic aspects of SARS-CoV-2 might aid in the development of a strategy for virus detection and the control of viral dissemination. To date, natural infection with SARS-CoV-2 has been reported in cats, dogs, mink, otter, pet ferrets, lions, tigers, pumas, snow leopards, gorillas, white-tailed deer, fishing cat, Binturong, South American coati, spotted hyena, Eurasian lynx, Canada lynx, hippopotamus and hamster (COVID-19 - OIE - World Organisation for Animal Health; Jo et al., 2021; Decaro et al., 2020a; Delahay et al., 2021; Fenollar et al., 2021; Gortázar et al., 2021; Palmer et al., 2021; Clayton et al., 2022).
However, it has not been detected in farm animals, such as buffaloes, goats, sheep, horses, rabbits, hens, pigs, or cows, despite contact with their SARS-CoV-2-positive human breeders for at least 2 weeks (Cerino et al., 2021). The unknown zoonotic potential of this virus is a cause of concern for pet owners and farmers.
In April 2021, we investigated cattle on a farm, at which 13/20 farmworkers previously had COVID-19-associated disease, and one of them had died, for the presence of SARS-CoV-2 and BCoV. The farm is located in Ariano Irpino, the first city in the Campania region (Southern Italy) to be locked down and declared a red zone in March 2020.
This study is the first to describe natural SARS-CoV-2 infection in cattle. We hypothesise that this may represent a case of inverse zoonosis, that is human-to-animal transmission, which may lead to new reservoirs for the virus as well as the development of new viral variants that are potentially dangerous to humans and/or animals.
MATERIALS AND METHODS