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The decision this week by the Danish government to kill millions of mink over coronavirus concerns, effectively wiping out a large domestic industry, has highlighted simmering concerns among scientists and conservationists about the vulnerability. from animals to pandemic virus, and what infections in animals might mean for humans.
The most worrying possibility is that the virus could mutate in animals and become more transmissible or more dangerous to humans. In Denmark, the virus has passed from humans to mink and back to humans, and mutated in the process. Mink are the only animals known to have transmitted the coronavirus to humans, except for the initial spillover event of an unknown species. Other animals, such as cats and dogs, have been infected through exposure to humans, but there are no known cases of people infected through exposure to their pets.
The versions of the virus that have mutated in mink and spread to humans are not more transmissible or cause more serious illness in humans. But one of the variants, so far found in 12 people, was less susceptible to antibodies in lab tests. Danish health authorities feared that the effectiveness of vaccines under development might be diminished for this variant and decided to take all possible measures to stop its spread. This involved killing all the mink in the country and effectively locking down the northern part of the country, where the mutated virus was found. The UK has banned travelers from Denmark who are not UK citizens.
The World Health Organization and scientists outside of Denmark said they had yet to see evidence that this variant would have an effect on vaccines. They did not, however, criticize Denmark’s decision to slaughter its mink population.
Mink are not the only animals that can be infected with the coronavirus. Genetically modified dogs, cats, tigers, hamsters, monkeys, ferrets and mice have also been infected.
Dogs and cats, including tigers, seem to suffer from few adverse effects. The other animals, which are used in laboratory experiments, exhibited varying responses. However, farmed mink have died in large numbers in Europe and the United States, perhaps in part due to the overcrowded conditions on these ranches, which could increase the level of exposure.
Public health experts fear, however, that any species susceptible to infection will become a reservoir for the virus to re-emerge at any time and infect humans. The virus would probably mutate in other animal species, as has been shown in mink. While most mutations are probably harmless, SARS-CoV-2 could likely recombine with another coronavirus and become more dangerous. Conservation experts are also concerned about the effect on already struggling animal species.
One approach to studying sensitivity has been to look at the genomes of the animals and see which ones have a genetic sequence that encodes a protein on cells called the ACE2 receptor, which allows the virus to attach itself. A team of researchers studied the genomes of more than 400 animals. Another group carried out a similar study on primates, which are often infected with human respiratory viruses.
“One of the premises of this research was that we thought that great apes would be very at risk because of their close relationship with humans, genetically,” said Amanda D. Melin, anthropologist at the University of Calgary and author. of the study of primates.
But, she added, she and her colleagues also wanted to consider “all other primates and their potential risk.” In addition to studying genomes, the team also computerized the interaction of the virus spike protein with different ACE2 receptors.
The findings of the two articles are mutually reinforcing, revealing that old world monkeys and all apes are most at risk. Both papers were published as non-peer reviewed studies earlier this year.
Dr. Melin and her colleagues spoke with representatives from wildlife sanctuaries and zoos about the need to be careful. Many of these facilities have increased restrictions for interactions between humans and primates.
Zarin Machanda, of Tufts University, who studies chimpanzee behavior at the Kibale Chimpanzee Project in Uganda, said the reserve had increased its safety precautions due to the pandemic.
“We are always careful with respiratory viruses,” she says, because these viruses are the leading cause of death in Kibale chimpanzees. Even the common cold can be fatal.
Chimpanzees have suffered from outbreaks of other coronaviruses. Normally, humans in Kibale maintain a minimum distance of two dozen feet from chimpanzees; that has been increased to 30 feet or more. Local workers stayed on the reserve, rather than commuting between their communities. And the project reduced the hours spent on field studies. All of these measures were led by the Ugandan government.
Tony Goldberg, a veterinarian at the University of Wisconsin, Madison, and head of the Kibale EcoHealth Project, said he has witnessed the devastation caused by respiratory disease in chimpanzees. A fatal outbreak in 2013 in the reserve was found to be the result of human rhinovirus C, the most common cause of the common cold worldwide. Until then, it had never been seen in chimpanzees.
“The last thing we need is for SARS-CoV-2 to travel to an animal reservoir where it could reemerge,” Dr Goldberg said.
Other researchers are studying species ranging from belugas to deer mice for signs of the coronavirus. Kate Sawatzki, animal surveillance coordinator for a companion animal and other animal testing project at the Cummings School of Veterinary Medicine at Tufts University, said: “To date, we have tested 282 samples of wild animals from 22 species, mainly bats, in rehabilitation centers in New England. , and we’re happy to report that none have been positive. “
They also tested 538 pets, including households with people with Covid-19, and none showed signs of an active virus. However, said Dr Sawatzki, the lab also performed blood tests for antibodies, showing exposure, and they found antibodies there, as is common in humans. The animals appeared to be infected but did not get sick or transmit the virus.
So far, mink in Denmark is the only known case of the virus infecting an animal, molting and transferring to humans. Emma Hodcroft of the University of Basel, Switzerland, traces various mutated versions of the coronavirus as it spread in Europe and has reviewed scientific information released by Danish health authorities. She said she applauded the government’s decision to act quickly and kill the mink: “Many countries have hesitated and waited before acting, and it can be incredibly damaging in the face of SARS-CoV-2, like we see it.
But she did not approve of the way the information was published, particularly in the government press briefing on Wednesday, which warned of a serious threat to potential human vaccines, but did not provide any details on this concern. “The communication of science could have been much clearer and led to less concern in the world,” said Dr Hodcroft.
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