Natural SARS-CoV-2 infection in farmed minks

Introduction: In 2020, the first disease outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in farmed minks Methods: To better understand the dynamics of viral spread and disease progression after natural infection, this study investigates the pathology, immunohistochemistry, virology, serology, proteomics, and the presence of Aleutian Disease Virus (ADV) in minks from an infected farm. A total of 45 minks were divided into four groups based on clinical health status and time of sampling: found dead before culling (FD, Results: Histopathological examination revealed that interstitial pneumonia was the most prominent SARS-CoV-2-related finding across all four groups, with more severe lesions seen in the FD and FDc groups. Histopathological changes were supported by viral antigen expression in the nose, trachea, and lungs, as well as in extra-respiratory tissues such as the intestine, spleen, and lymph nodes, in all groups. Highest viral RNA levels were found in nasal and throat swabs and nose and lung tissues. Lower levels were detected in the spleen, liver, and intestine, especially in the FDc animals. Serology confirmed the presence of SARS-CoV-2 specific antibodies in all groups, whereas immune-related proteomics on whole blood did not show a significant difference between the groups. Based on qPCR, over 57% of minks were co-infected with ADV. Discussion: Minks naturally infected with SARS-CoV-2 exhibit severe lung pathology and high viral loads across multiple organs. Additionally, severe lung lesions are also observed in animals without clinical signs, suggesting a potential zoonotic risk and viral spread in the absence of any clinical signs.