Abstract
SARS-CoV-2 infection outbreaks in minks have serious implications associated with animal health and welfare, and public health. In two naturally infected mink farms (A and B) located in Greece, we investigated the outbreaks and assessed parameters associated with virus transmission, immunity, pathology, and environmental contamination. Symptoms ranged from anorexia and mild depression to respiratory signs of varying intensity. Although the farms were at different breeding stages, mortality was similarly high (8.4% and 10.0%). The viral strains belonged to lineages B.1.1.218 and B.1.1.305, possessing the mink-specific S-Y453F substitution. Lung histopathology identified necrosis of smooth muscle and connective tissue elements of vascular walls, and vasculitis as the main early key events of the acute SARS-CoV-2-induced broncho-interstitial pneumonia. Molecular investigation in two dead minks indicated a consistently higher (0.3–1.3 log10 RNA copies/g) viral load in organs of the male mink compared to the female. In farm A, the infected farmers were responsible for the significant initial infection of 229 out of 1,000 handled minks, suggesting a very efficient human-to-mink transmission. Subsequent infections across the sheds wherein animals were being housed occurred due to airborne transmission. Based on a R0 of 2.90 and a growth rate equal to 0.293, the generation time was estimated to be 3.6 days, indicative of the massive SARS-CoV-2 dispersal among minks. After the end of the outbreaks, a similar percentage of animals were immune in the two farms (93.0% and 93.3%), preventing further virus transmission whereas, viral RNA was detected in samples collected from shed surfaces and air. Consequently, strict biosecurity is imperative during the occurrence of clinical signs. Environmental viral load monitoring, in conjunction with NGS should be adopted in mink farm surveillance. The minimum proportion of minks that need to be immunized to avoid outbreaks in farms was calculated at 65.5%, which is important for future vaccination campaigns.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new member of the Betacoronavirus genus (Coronaviridae family), responsible for the coronavirus disease 2019 (COVID-19), a human disease which most likely has emerged as a spill-over from wild animals and became a pandemic through widespread human-to-human transmission [1,2]
SARS-CoV-2 infection outbreaks in minks were first reported on April 2020
As this condition is important for both minks and humans, we investigated natural infection outbreaks in 2 mink farms at different breeding stages
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new member of the Betacoronavirus genus (Coronaviridae family), responsible for the coronavirus disease 2019 (COVID-19), a human disease which most likely has emerged as a spill-over from wild animals and became a pandemic through widespread human-to-human transmission [1,2]. The viral receptor-binding domain recognizes ACE2 from various animal species, including species belonging in the Mustelidae family [4]. European (Mustela vison) and American (Neovison vison) minks are members of the weasel family (Mustelidae). Their susceptibility, as well as their capability to transmit SARS-CoV-2 has been confirmed via experimental infection studies in ferrets [9,10] and subsequently, through outbreaks in American minks. Natural SARS-CoV-2 infection in farmed American minks was first reported on April 2020, in the Netherlands [11,12]. Thenceforth, the number of SARS-CoV-2 infection cases recorded in minks farmed
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