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. 2022 Jan 21:8:805004.
doi: 10.3389/fvets.2021.805004. eCollection 2021.

SARS-CoV-2 Outbreak on a Spanish Mink Farm: Epidemiological, Molecular, and Pathological Studies

Juan José Badiola  1 , Alicia Otero  1 , Eloisa Sevilla  1 , Belén Marín  1 , Mirta García Martínez  1 , Marina Betancor  1 , Diego Sola  1 , Sonia Pérez Lázaro  1 , Jenny Lozada  1 , Carolina Velez  2 , Álvaro Chiner-Oms  3 , Iñaki Comas  4 , Irving Cancino-Muñoz  3 , Eva Monleón  1 , Marta Monzón  1 , Cristina Acín  1 , Rosa Bolea  1 , Bernardino Moreno  1
Affiliations

SARS-CoV-2 Outbreak on a Spanish Mink Farm: Epidemiological, Molecular, and Pathological Studies

Juan José Badiola et al. Front Vet Sci. .

Abstract

Farmed minks have been reported to be highly susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and may represent a risk to humans. In this study, we describe the first outbreak of SARS-CoV-2 occurred on a mink farm in Spain, between June and July 2020, involving 92,700 animals. The outbreak started shortly after some farm workers became seropositive for SARS-CoV-2. Minks showed no clinical signs compatible with SARS-CoV-2 infection throughout the outbreak. Samples from 98 minks were collected for histopathological, serological, and molecular studies. Twenty out of 98 (20.4%) minks were positive by RT-qPCR and 82 out 92 (89%) seroconverted. This finding may reflect a rapid spread of the virus at the farm with most of the animals overcoming the infection. Additionally, SARS-CoV-2 was detected by RT-qPCR in 30% of brain samples from positive minks. Sequencing analysis showed that the mink sequences were not closely related with the other mink SARS-CoV-2 sequences available, and that this mink outbreak has its probable origin in one of the genetic variants that were prevalent in Spain during the first COVID-19 epidemic wave. Histological studies revealed bronchointerstitial pneumonia in some animals. Immunostaining of viral nucleocapsid was also observed in nasal turbinate tissue. Farmed minks could therefore constitute an important SARS-CoV-2 reservoir, contributing to virus spread among minks and humans. Consequently, continuous surveillance of mink farms is needed.

Keywords: SARS-CoV-2; Spain; antibodies; mink; polymerase chain reaction; sequence.

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Conflict of interest statement

This study received funding from Banco Santander S.A. and University of Zaragoza. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Maximum-likelihood phylogeny constructed using the genomic sequences obtained from mink samples and all the complete sequences processed by the SeqCOVID consortium at 15/09/2021. (A) Phylogeny tree; (B) A zoomed view of the phylogeny, focusing on the SEC3 clade.
Figure 2
Figure 2
Gross and microscopic pulmonary lesions in minks infected with SARS-CoV-2. (A) Gross lesions are characterized by irregular dark areas of consolidation in the lungs of infected minks (left). Right panel shows the lungs from a non-infected, healthy mink not presenting dark consolidated areas. (B) Perivascular inflammatory infiltrates and bronchointerstitial pneumonia with alveolitis are observed in one positive mink (H-E, x100). (C) Thickened alveolar walls by inflammatory infiltrates in one positive mink (H-E, x50). (D) Normal histological features in the lung of a mink negative for SARS-CoV-2. (E) Marked proliferation of T lymphocytes in the lung interstitium of one positive mink, confirmed by immunohistochemistry using an anti-CD3 antibody (x50). (F) Magnified capture of (E) showing immunopositive T lymphocytes (x100).
Figure 3
Figure 3
Immunohistochemical detection of SARS-CoV-2 nucleoprotein in mink tissues. (A) Detection of SARS-CoV-2 N protein in the olfactory epithelium (x400). (B) Immunodetection for N protein was also detected in olfactory neurons (x400). (C) No immunopositivity was detected in brain samples although viral RNA was amplified by RT-PCR in three animals (x100).
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