An outbreak of SARS-CoV-2 with high mortality in mink (Neovison vison) on multiple Utah farms

Abstract

The breadth of animal hosts that are susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and may serve as reservoirs for continued viral transmission are not known entirely. In August 2020, an outbreak of SARS-CoV-2 occurred in multiple mink farms in Utah and was associated with high mink mortality and rapid viral transmission between animals. The outbreak's epidemiology, pathology, molecular characterization, and tissue distribution of virus within infected mink is provided. Infection of mink was likely by reverse zoonosis. Once established, infection spread rapidly between independently housed animals and farms, and caused severe respiratory disease and death. Clinical signs were most notably sudden death, anorexia, and increased respiratory effort. Gross pathology examination revealed severe pulmonary congestion and edema. Microscopically there was pulmonary edema with moderate vasculitis, perivasculitis, and fibrinous interstitial pneumonia. Reverse transcriptase polymerase chain reaction (RT-PCR) of tissues collected at necropsy demonstrated the presence of SARS-CoV-2 viral RNA in multiple organs including nasal turbinates, lung, tracheobronchial lymph node, epithelial surfaces, and others. Whole genome sequencing from multiple mink was consistent with published SARS-CoV-2 genomes with few polymorphisms. The Utah mink SARS-CoV-2 strain fell into Clade GH, which is unique among mink and other animal strains sequenced to date and did not share other spike RBD mutations Y453F and F486L found in mink. Localization of viral RNA by in situ hybridization revealed a more localized infection, particularly of the upper respiratory tract. Mink in the outbreak reported herein had high levels of virus in the upper respiratory tract associated with mink-to-mink transmission in a confined housing environment and were particularly susceptible to disease and death due to SARS-CoV-2 infection.

The origins and molecular evolution of SARS-CoV-2 lineage B.1.1.7 in the UK

“…Further, it is unlikely that a variant so effective at spreading in the human population would have evolved in a non-human population; as the mutations required to be successful in a human population may well be different due to differences in cell receptors, as well as behaviour. Common mutations appear in animal populations, such as N501T and Y453F in mink across different continents (Eckstrand et al 2021;Lu et al 2021), but are rarely found in human infections, and not in any of the VOCs. While it would be possible for a two-step evolutionary process wherein there is first some adaptation in an animal population, allowing the crossing of a fitness valley, followed by spillover and human adaptation through conventional transmission, it would once again be difficult to explain the intermediate sample we observe through this transmission process.…”

Household transmission of SARS-CoV-2 from humans to pets in Washington and Idaho: burden and risk factors

“…Respiratory or fecal swabs: RNA extraction and SARS-Cov-2 reverse transcriptase (RT) real-time PCR was performed as described [18]. Following initial viral detection by PCR, three dog samples and one cat sample were submitted to University of Minnesota Genomics Center (Oakdale, MN 55128) for whole genome sequencing (WGS) [19].…”

Susceptibility of wild canids to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

“…In the vast majority of cases, non-human animals seem to experience subclinical or mild disease following infection with SARS-CoV-2. There are exceptions -infected mink, large felids in zoos, and the occasional pet dog or cat have presented with signs of a respiratory infection, including coughing, sneezing, ocular/nasal discharge, and increased respiratory effort (30)(31)(32). More severe disease has also been observed, with a report out of the United Kingdom hypothesizing that SARS-CoV-2 infection may be linked to myocarditis in pet dogs and cats (18), and mink farms reporting increased mortality during SARS-CoV-2 outbreaks (30).…”

“…There are exceptions -infected mink, large felids in zoos, and the occasional pet dog or cat have presented with signs of a respiratory infection, including coughing, sneezing, ocular/nasal discharge, and increased respiratory effort (30)(31)(32). More severe disease has also been observed, with a report out of the United Kingdom hypothesizing that SARS-CoV-2 infection may be linked to myocarditis in pet dogs and cats (18), and mink farms reporting increased mortality during SARS-CoV-2 outbreaks (30). Thus far, only a few animal species have demonstrated the ability to transmit virus to naïve conspecifics (deer mice, cats, ferrets, raccoon dogs, and white-tailed deer), and mink are the only animals that have definitively infected humans (33)(34)(35).…”