The conclusion is not quite as hard as nails, but most likely a mink with Covid-19 has infected an employee at a mink farm in North Brabant. This is evident from a study commissioned by the Ministry of Agriculture, Nature Management and Fisheries. That is a world first. It would be the first time that the new coronavirus SARS-CoV-2 has been caught from an animal to human infection.
Research leader Arjan Stegeman, veterinary epidemiologist at the Faculty of Veterinary Medicine at Utrecht University, emphasizes that the conclusion has not yet been established. “It is not without reason that Minister Schouten used the word plausibly in her letter to the House of Representatives about this.”
But the combination of genetic research and an inventory of the circumstances makes it very plausible that the employee was infected by minks, says Stegeman. “The hereditary code of the virus that we found in the employee is more closely related to that of the virus in mink than the now known codes of the virus in humans. This person had only been working at the company for a few weeks. That also corresponds to the scenario. Thirdly, our research showed that people in the barn are exposed to the virus, for example through dust particles that can be easily inhaled. ”
The research team wants to further substantiate the findings by also determining as many virus sequences as possible from Covid-19 patients in the vicinity of the breeding farms. “Then we hope to see how the mink viruses are rooted in viruses in people in the region. But that research is not yet complete. ”
The investigation began after two mink farms found that the animals were infected with SARS-CoV-2 on April 26. On May 7, minks were also infected with the virus at two other companies. All these companies are located in the east of the province of Noord-Brabant, where there were also many human infections at the beginning of the epidemic.
Transfer from mink to mink
More conclusions can be drawn from the genetic sequences of the viruses that the team mapped in collaboration with the virology group of Erasmus MC’s Marion Koopmans, says Stegeman. “The variation in viruses on one mink farm is much greater than the variation we see, for example, in an outbreak in a nursing home. This means that there must have been a transfer from mink to mink. We also see that the virus infections in the first two companies came from a very different source to humans. ”
Three companies are in the same place in the genetic family tree of the virus. There is a clear link between two of those companies. The other company is investigating whether feral cats may have transmitted the virus. Stegeman: “For cats, a mink barn is a land of lazy, they love mink food and can easily access it in the barn. Although the companies are fenced, cats always find a way to get in. ”
Eleven feral cats were caught on the farm “with some difficulty”, three of which had antibodies against the virus in their blood. The virus itself was no longer found. “These cats have been spayed or neutered before being released. That helps prevent them from spreading over a wide area. ”
Infectious animal disease
In response to the research results, Minister of Agriculture Carola Schouten (ChristenUnie) has decided to designate infection with SARS-CoV-2 in mink as an infectious animal disease. This not only means that the infection becomes obliged to report, but also that far-reaching measures can be taken if necessary, such as in the most extreme case the removal of infected companies. All mink companies are now legally required to have their animals tested for antibodies to see if they have had the virus.
“As long as the infection is actively circulating in the animals, and which therefore excrete viruses, there is a risk for people in the immediate vicinity,” says virologist Marion Koopmans. “It is no different than around a human patient.” For this reason, all employees of mink farms must wear personal protection.
“It is expected that this infection will blow through the farms,” says Koopmans, “and that if many animals have built up immunity, it will stop spreading.”
But whether that is the case, the research will have to show, says Stegeman: “We have to be alert that it stops. Currently, the risk of mink contamination to humans is still negligible, compared to the risk of infecting other people. Out of the three and a half million infections worldwide between people, there is now one from mink to human. But soon, in the tail end of the epidemic, you don’t want a reservoir of viruses left in mink farms. ”