Uncertainty surrounding the implications of the discovery of a Covid-19 mink variant in humans led Denmark, the world’s largest producer of mink fur, to launch a nationwide cull earlier this month.
The slaughter was triggered by research by Denmark’s public health agency, the Statens Serum Institut (SSI), which showed that a variant of mink called C5 was more difficult for antibodies to neutralize and posed a threat potential for vaccine efficacy.
Denmark, the Netherlands, South Africa, Switzerland, the Faroe Islands, Russia and the United States have all reported cases of mutations linked to mink.
Despite a political backlash, the slaughter continued and farmers have until midnight Thursday to slaughter all the mink in the country. However, the dispute over the slaughter forced the resignation of Danish Agriculture Minister Mogens Jensen.
SSI director Kåre Mølbak also said he would step down. It was SSI’s findings on reduced antibody effectiveness that led to the slaughter order. Mølbak told local media he was retiring because he was 65 and denied it was related to mink slaughter.
So far, there had been no widespread reports of mink variants in humans outside of Denmark. But scientists uploading information about virus sequencing and variants to Gisaid, a global database initiative, said there were signs of mink variants around the world.
“We knew there were these mink variants in seven countries, but we only had about 20 genomes of each, which is very few. Then last week, the Danes uploaded 6,000 genomic sequences and with those we were able to identify 300 or more of the mink variant Y453F in viruses that infected humans in Denmark, ”said François Balloux, director of University of London Institute of Genetics (UCL).
Asked about the implications of the results, Balloux said it was an indication of the need to slaughter farmed mink. “A larger host reservoir means more infections in humans. The main point here, I think, is that while the mutation isn’t scary, there are still very good reasons to get rid of the mink tank. We just don’t need it. In Denmark, he added, they have a lot of mink, “more than three times as many as humans”.The prevalence of Danish mink mutations is evident in the Gisaid database. “Denmark has 329 F variant sequences, which match roughly as many individuals, although there may be duplicates,” said Professor Seshadri Vasan from York University, who analyzed the database. data for mink variants. “The Netherlands have six. South Africa and Switzerland have two each, while the Faroe Islands, Russia and Utah [US] have one each. ”
Asked how the spread could have happened, Vasan said that given that some of the human and mink F variants came from samples taken in Denmark in June, it could be that “the movement of people, of animals or goods could have propagated variant F to other countries ”.
But, since the Gisaid database only includes incomplete patient information and no travel history – and some samples lack collection dates – he said it was impossible to say exactly how and when. the spread has taken place, although local scientists may be in a better position to understand.
Last month, Vasan and his team released a comprehensive model to improve the collection and sharing of information about anonymized patients with the aim of improving data quality.
Viruses are known to mutate, but variants alone are not necessarily a problem. More importantly, said UCL microbiologist Prof Joanne Santini, we still don’t know whether this mutation first occurred in mink or in humans.
In a joint email to the Guardian this week, Santini and her colleague at UCL, Bioethicist Professor Sarah Edwards said the Sars-CoV-2 Y453F variant in the spike protein is “unlikely to present a serious risk for the expected efficacy of current candidate vaccines. , or in itself constitutes a new threat to public health ”.
If, however, the variant originated in mink and spread to humans, “then we should doubt our ability to manage outbreaks in apparently confined livestock once detected.”
The constant mutations could also be a cause for concern. The email added that “several additional variants of the spike protein could indeed have worrying implications on the degree of infection of the virus for humans and also for animals”, potentially posing “new threats to the virus. ‘expected efficacy of our candidate vaccines’.
“The first observations of CSIRO [Commonwealth Scientific and Industrial Research Organisation] scientists demonstrate the possible implications for the wider spread of Sars-CoV-2 variants between humans and animals, ”she said.
Although Denmark is the only country to order a nationwide mink slaughter, others, including the Netherlands, Spain and, more recently, Greece, are killing mink with Covid-19. On Tuesday, Reuters reported that mandatory testing of mink had started in Poland, despite industry fears that the testing could lead to a nationwide slaughter.
On the commercial side, the Danish slaughter had immediate effects. Last week, the Danish Breeders Association and the world’s largest fur auction house, Kopenhagen Fur, announced a “controlled shutdown” over the next three years, while Danish thinktank estimates assess the cost of mink farm closures to around DKK 3 billion (£ 360 million).
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