Comparative analysis of serological assays and sero-surveillance for SARS-CoV-2 exposure in US cattle (preprint)

Coronavirus disease-2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continues to pose a significant threat to public health globally. Notably, SARS-CoV-2 demonstrates a unique capacity to infect various non-human animal species, documented in captive and free-living animals. However, experimental studies revealed low susceptibility of domestic cattle (Bos taurus) to ancestral B.1 lineage SARS-CoV-2 infection, with limited viral replication and seroconversion. Despite the emergence of viral variants with potentially altered host tropism, recent experimental findings indicate greater permissiveness of cattle to SARS-CoV-2 Delta variant infection compared to other variants, though with limited seroconversion and no clear evidence of transmission. While some studies detected SARS-CoV-2 antibodies in cattle in Italy and Germany, there is no evidence of natural SARS-CoV-2 infection in cattle from the United States or elsewhere. Since serological tests have inherent problems of false positives and negatives, we conducted a comprehensive assessment of multiple serological assays on over 600 cattle serum samples, including pre-pandemic and pandemic cattle sera. We found that SARS-CoV-2 pseudovirus neutralization assays with a luciferase reporter system can produce false positive results, and care must be taken to interpret serological diagnosis using these assays. We found no serological evidence of natural SARS-CoV-2 infection or transmission among cattle in the USA. Hence, it is critical to develop more reliable serological assays tailored to accurately detect SARS-CoV-2 antibodies in cattle populations and rigorously evaluate diagnostic tools. This study underscores the importance of robust evaluation when employing serological assays for SARS-CoV-2 detection in cattle populations.

Systemic infection of SARS-CoV-2 in free ranging Leopard (Panthera pardus fusca) in India (preprint)

We report patho-morphological and virological characterization of SARS-CoV-2 in naturally infected, free ranging Indian Leopard (Panthera pardus fusca). Whole genome sequence analysis confirmed infection of Delta variant of SARS-CoV-2, possibly spill over from humans, but the case was detected when infection level had dropped significantly in human population. This report underlines the need for intensive screening of wild animals for keeping track of the virus evolution and development of carrier status of SARS-CoV-2 among wildlife species.