Infection, recovery and re-infection of farmed mink with SARS-CoV-2

Rasmussen, Thomas Bruun; Fonager, Jannik; Sværke Jørgensen, Charlotte; Lassaunière, Ria; Hammer, Anne Sofie; Quaade, Michelle Lauge; Boklund, Anette; Lohse, Louise; Strandbygaard, Bertel; Rasmussen, Morten; Michaelsen, Thomas Yssing; Mortensen, Sten; Fomsgaard, Anders; Belsham, Graham J.; Bøtner, Anette

Mink, on a farm with about 15,000 animals, became infected with SARS-CoV-2. Over 75% of tested animals were positive for SARS-CoV-2 RNA in throat swabs and 100% of tested animals were seropositive. The virus responsible had a deletion of nucleotides encoding residues H69 and V70 within the spike protein gene. The infected mink recovered and after free-testing of the mink, the animals remained seropositive. During follow-up studies, after a period of more than 2 months without virus detection, over 75% of tested animals scored positive again for SARS-CoV-2 RNA. Whole genome sequencing showed that the virus circulating during this re-infection was most closely related to the virus identified in the first outbreak on this farm but additional sequence changes had occurred. Animals had much higher levels of anti-SARS-CoV-2 antibodies after re-infection than at free-testing. Thus, following recovery from an initial infection, seropositive mink rapidly became susceptible to re-infection by SARS-CoV-2. Article Summary Line Following widespread infection with SARS-CoV-2 of mink on a farm, all tested animals had seroconverted and the farm was then tested free of infection; however, less than 3 months later, a further round of infection affected more than 75% of tested animals.