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

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.

Household transmission of SARS-CoV-2 from humans to dogs in Washington and Idaho: burden and risk factors (preprint)

Background: SARS-CoV-2 is believed to have emerged from an animal reservoir as a zoonotic pathogen. Over the course of the current pandemic, evidence has mounted that infected humans can transmit the virus to animals including household pets, however the frequency of and risk factors for this transmission remain unclear. We carried out a community-based study of pets in households with one or more confirmed SARS-CoV-2 case among the human residents, and report here on interim findings from sampling of dogs. Methods: Data collection included a survey of human and animal demographic and clinical variables, features of their shared environment, and human-animal contact; blood collection from animals for serology for anti-SARS-CoV-2 antibodies; and nasopharyngeal sampling for PCR testing for SARS-CoV-2. Results: Sampling consisted of 67 dogs from 46 households. Nasopharyngeal PCR testing results were available for 58 dogs, and serological testing results were available for 51. Clinical signs consistent with COVID-19 were reported in 14 dogs (23.7%, 95% CI 0.13, 0.35), and SARS-CoV-2 antibody testing using viral receptor binding domain ELISA was positive in 22 dogs (43.1%, 95% CI 0.30, 0.57). All PCR tests of nasopharyngeal swabs were negative. Survey respondents commonly reported close human-animal contact, and the majority of households were aware of and adopted measures to mitigate human-to-animal transmission of SARS-CoV-2 following diagnosis. While no statistically significant associations were detected between human-animal contact variables and either seropositivity or COVID-19 like illness in dogs, positive trends were found for sharing beds with humans and the number of SARS-CoV-2 positive humans in the corresponding household. Reported measures taken by the household to mitigate transmission showed a protective trend, and COVID-19 like illness in a dog was positively associated with seropositivity in that dog. Discussion: These data indicate that human-to-animal transmission of SARS-CoV-2 in households is common, in a study population characterized by close human-animal contact. They also indicate that infected pets often manifest signs of COVID-like illness. While nasopoharyngeal sampling of dogs in this study has not to date demonstrated positive PCR results, this could be due to delays in sampling. Household members reported taking precautions to protect pets from SARS-CoV-2 infection, indicating an opportunity for further measures to reduce transmission of SARS-CoV-2 between people and animals sharing households.