Mink cages (in Denmark 2020): constant source of infection?
Photo: Mads Claus Rasmussen / dpa
An outbreak of bird flu on a Spanish mink farm has experts worried.
They see signs that the H5N1 virus is adapting to mammals and could become more dangerous to humans as a result.
The pathogens had previously been found in other mammal species such as raccoons, foxes, martens or seals, said Thomas Mettenleiter, President of the Friedrich Loeffler Institute for Animal Health, the dpa news agency.
So far, however, there have been individual events in which the virus has passed from a bird to a mammal.
With the outbreak in Spain last October, however, it could be that “the pathogen really spread from mammal to mammal – i.e. from mink to mink”.
Other researchers also consider this to be possible or probable.
The events in Spanish mink breeding could have been an indication of a further adaptation step of the virus, says Mettenleiter.
The first animals died on a farm in the northwestern region of Galicia in autumn 2022, Science magazine reported.
At first, veterinarians assumed that the coronavirus was the trigger.
But tests showed that the H5N1 virus had led to the deaths.
As a result, the farm's more than 50,000 mink were killed and their carcasses destroyed.
The employees did not become infected.
A few days ago, an analysis of the case was published in the magazine »Eurosurveillance«.
The largest outbreak of avian influenza ever documented is currently rampant among birds.
It extends over several continents.
This gives the pathogen more opportunities to spread to mammals.
In addition, the cramped conditions in which the mink were kept were conducive to such a possible spread among these animals, says Mettenleiter.
The event in Spain was “definitely a warning signal”.
Mink breeding as breeding ground for mutations?
Tom Peacock, a virologist at Imperial College London, was even more drastic.
"This is incredibly worrying," he told Science magazine.
For him, this is “a clear mechanism for how an H5 pandemic could start”.
Since the receptors to which the virus docks in the airways of birds are rarer in mammals, they are usually spared the infection, according to Science.
However, they could become ill, for example, by ingesting wild bird droppings or preying on infected birds, Hualan Chen, a virologist at the Harbin Veterinary Medical Research Institute in China, told Nature magazine.
Spread among mammals, on the other hand, indicates a greater risk to public health.
According to the "Science" report, it is not known how easily the virus found in mink can also infect humans or spread among them.
However, several mutations were found in virus samples from four animals.
One of them contributes to the H5N1 virus being able to multiply better in mammalian tissue.
The bird flu outbreak highlights the risks of mink farming once again.
Even the corona virus, which was brought into mink farms by humans, has spread rapidly among the animals.
Researchers fear the mink industry could become a constant source of infection and a breeding ground for viral mutations.
Bird flu has been plaguing Europe on a regular basis for years.
While the pathogen in connection with bird migration in the past occurred in this country mainly in the cold season, there have recently been infections throughout the year.
The currently dominant virus is considered harmless to humans.