They look so cute and cuddly! I’m not talking about the Giant Microbes SARS CoV2 toys (gosh they do make great bugs, don’t they?!). No, I’m talking about mink! Well I like them…But personally, I think mink coats look better on mink!
Maybe Covid-19 is going to finally put an end to the production of fur coats… I can but hope. What am I talking about? This is a microbiology blog, not a rant against animal fur in fashion… or is it?
So last week, before all the vaccine shenanigans (Congrats to Oxford; at least their vaccine interim results are published in the Lancet not just the BBC!), I was going to write a blog about Covid-19 and mink. So, what was this all about?
Last week it was reported that there was a new strain of SARS CoV2 which had transferred from mink into humans, and that there was no protection even if you had had Covid-19. The way it was reported would have us all believing that another new pandemic was about to start….
Maybe Covid-19 is going to finally put an end to the production of fur coats… I can but hope. What am I talking about? This is a microbiology blog, not a rant against animal fur in fashion… or is it?
So last week, before all the vaccine shenanigans (Congrats to Oxford; at least their vaccine interim results are published in the Lancet not just the BBC!), I was going to write a blog about Covid-19 and mink. So, what was this all about?
Last week it was reported that there was a new strain of SARS CoV2 which had transferred from mink into humans, and that there was no protection even if you had had Covid-19. The way it was reported would have us all believing that another new pandemic was about to start….
What are mink?
Mink are small carnivorous mammals in the family Mustelidae, along with ferrets, weasels and otters. We don’t have a native mink in the UK; the European mink apparently never made it to these shores. However, we do have American mink though, after they were imported for fur farming in 1929. Shortly after that they became naturalised either because of escapees or deliberate releases from fur farms by animal activists. They were first reported to be breeding wild in 1956. Fur farming was big business in the UK (400 known fur farms in the UK at its peak in the 1950s), although fur started to “go out of fashion” towards the end of the last century and was finally banned in the UK in 2000. Ecologically mink cause an issue (like most introduced species!) as they prey on our native water vole which is now a priority species according to the UK Biodiversity Action Plan; apparently in pre-Roman times water voles were our commonest small mammal! Whatever the reason we now have wild mink in the UK…and mink can get Covid-19!
Is it a surprise that mink can have SARS CoV2?
It should come as no surprise that mink can be infected with SARS CoV2. One of the best animal models for investigating the transmission of coronaviruses, including SARS CoV2, is the ferret. Ferrets can be infected with SARS CoV2, but do not become that unwell, and so they are “good” for studying how the virus transmits between individuals. Coincidentally mice are a “rubbish” model unless they have been genetically altered, as normal mice aren’t able to be infected with SARS CoV2.
So, if ferrets can be infected with SARS CoV2 then it is reasonable to assume that the related mink can also be infected. The most likely way mink first become infected is from us humans! But it turns out mink actually get quite sick with SARS CoV2 infection, so this makes it relatively easy to track cases of infection within the mink farms. So what!? I know we don’t have fur farms in the UK, but the Netherlands do…
April 2020 – Netherlands
Back in April of this year it was reported that there had been cases of Covid-19 associated with mink farms in the Netherlands, and this has subsequently been reported in the journal Science. So far mink on 16 farms have been infected, plus 67 out of 98 farm workers have tested positive for SARS CoV2 infection, either by PCR or antibody tests.
The investigators in the Netherlands compared the mink outbreak variants to human isolates, 1775 national and 34 local isolates, and found no exact matches. Although these are new variants, it should be reassuring as it suggests there has only been local transfer from humans to mink and back to humans; there has been no sustained wider transmission of the mink-related variants.
Another reassuring aspect of these outbreaks was that there was no particular variant of SARS CoV2 that predominated, there was a large diversity in the viruses, the number of mutations were small (maximum 12 nucleotide mutations) and the clinical presentation of the human cases was the same as other non-mink related cases.
Meanwhile in Denmark…!
June 2020 – Denmark
From June to November there have been 5 big clusters of SARS CoV2 infection in 200 mink farms, mainly from the North Jutland area of Denmark. Denmark has about 17 million mink in farms for the fur trade (that’s a lot of animals being farmed for their “fashionable” pretty fur).
Within Denmark there has been an ongoing study looking to see if there have been any human cases associated with mink farming. Isolates of viruses from patients across Denmark have been genetically sequenced and compared to those from mink. This has identified 214 cases of Covid-19 in humans associated with mink farms.
The studies done in Denmark have also looked to see if there are any mutations occurring in the SARS CoV2 virus; mutations might have implications for increased infectivity in humans or break through of natural or vaccine induced immunity. This is really important because if the virus is able to mutate in a particular way it might be able to bypass the hosts’ immune system causing recurrent infections or make a promising vaccine ineffective. In a way this is what Influenza Virus does every year, and why we have outbreaks of “Flu” every winter (and why we have a new flu vaccine every year… have you had yours yet?!)
Yep you guessed it, they found mutations! The media and even some scientific papers have called these “new strains of coronavirus”… but hang on!!! They are not. They are all “variants of SARS CoV2”; variants means “slightly different in form or function” (e.g. Cheddar, Wensleydale and Stilton are all variants of hard cheese). Whereas strain means, “a genetic difference… a specific type, quality, or character” (e.g. goats cheese is not cow’s milk cheese, brie is soft cheese, and Roquefort is ewe’s milk). The different strains of “coronaviruses” are SARS, MERS, SARS CoV2; the mink mutations are variants of the SARS CoV2 virus. A new strain is different and has pandemic potential whereas a variant is still the same virus and still “recognisable” as the original virus.
So far Denmark has seen 2 important mutations. One mutation increases the affinity of SARS CoV2 for the host cell’s ACE2 receptor which allows the virus to “enter the cell”. As the ACE2 receptor in mink is slightly different to that of human’s, the virus has mutated to a new variant that then allows it to better access into the mink’s cells. It is thought that this mutation leads to increased ability for SARS CoV2 to spread in mink. When this mutated variant transfers back to human’s it has also been found to be better able to bind to human ACE2 as well, which potentially makes this variant more infectious in humans.
The other variant they found in the Denmark mink has 4 mutations. These particularly mutations affect the spike protein which helps the virus “bind to host cells”. These spike proteins alter the body’s immune response which may not recognise the new variant as these spike proteins are the main target for both natural and vaccine induced antibodies against SARS CoV2. They found that in 9 patients who had previously recovered from Covid-19 this mutation appeared to make the virus 4 times less susceptible to their naturally derived antibodies. This means with another host (the mink) we could see repeated infections from mink to humans and repeated outbreaks due to sporadic reintroductions of “antibody resistant” virus. But I’m not going near mink!? But you never went near a bat either! It only needs one human to acquire the antibody resistant variant SARS CoV2 and spread it for there to be another outbreak. A resistant outbreak could be a big problem. So far 12 human cases of this antibody resistant variant have been identified in people with close contact with mink farming. Fortunately, their disease has followed the same course as the original Covid-19 cases, no better no worse.
At first glance it looks worrying that there are new variants of SARS CoV2 cropping up in animals in Europe but let’s just think about it for a moment. This virus will mutate over time; it’s a natural process. All life mutates eventually; humans are said to have a common ancestor “Lucy” and look how wonderfully genetically diverse we all are now. Viruses just do it faster! I wonder how different a SARS CoV2 isolate from a patient today in Texas would compare to an isolate from a patient in Denmark… if both isolates had a common ancestor in April and the virus mutated at the currently accepted rate of about 1 nucleotide every 2 weeks, the isolates could be 16-20 nucleotides different already… mink coat or Texan Stetson? Take your pick.
Originally the Danish Government wanted to cull all the 17 million mink in mink farms across the country but apparently this is now on hold because the Government do not have the legal right to order this, funny, money has got in the way! In the meantime the outbreak continues….
Why worry about mink?
Okay, so we can worry about mink being infected with SARS CoV2 and this making them sick and causing their suffering. The evidence of spill back from mink into humans is another worry, especially if the virus is undergoing mutation in the mink which might affect its ability to cause disease in humans. This is a good reason to take this seriously, but there is another concern.
What happens if a more common animal becomes infected from mink in mink farms? There will be lots of rodents such as rats and mice that could potentially become infected if the virus becomes modified in a mink host to make it possible to cross another species barrier. This hasn’t happened yet; remember mice can’t get SARS CoV2, but it is theoretically possible. This might then lead to a surge in cases if the source of infection is as common as a mouse… mice don’t physically distance and I’ve never seen one wearing a face mask! We would then be dealing with a zoonotic infection with an uncontrolled host, with bidirectional movement between humans and vector, and this would be a nightmare scenario. Cases of Covid-19 would soar.
But don’t panic, we’re not there yet.
Mink are small carnivorous mammals in the family Mustelidae, along with ferrets, weasels and otters. We don’t have a native mink in the UK; the European mink apparently never made it to these shores. However, we do have American mink though, after they were imported for fur farming in 1929. Shortly after that they became naturalised either because of escapees or deliberate releases from fur farms by animal activists. They were first reported to be breeding wild in 1956. Fur farming was big business in the UK (400 known fur farms in the UK at its peak in the 1950s), although fur started to “go out of fashion” towards the end of the last century and was finally banned in the UK in 2000. Ecologically mink cause an issue (like most introduced species!) as they prey on our native water vole which is now a priority species according to the UK Biodiversity Action Plan; apparently in pre-Roman times water voles were our commonest small mammal! Whatever the reason we now have wild mink in the UK…and mink can get Covid-19!
Is it a surprise that mink can have SARS CoV2?
It should come as no surprise that mink can be infected with SARS CoV2. One of the best animal models for investigating the transmission of coronaviruses, including SARS CoV2, is the ferret. Ferrets can be infected with SARS CoV2, but do not become that unwell, and so they are “good” for studying how the virus transmits between individuals. Coincidentally mice are a “rubbish” model unless they have been genetically altered, as normal mice aren’t able to be infected with SARS CoV2.
So, if ferrets can be infected with SARS CoV2 then it is reasonable to assume that the related mink can also be infected. The most likely way mink first become infected is from us humans! But it turns out mink actually get quite sick with SARS CoV2 infection, so this makes it relatively easy to track cases of infection within the mink farms. So what!? I know we don’t have fur farms in the UK, but the Netherlands do…
April 2020 – Netherlands
Back in April of this year it was reported that there had been cases of Covid-19 associated with mink farms in the Netherlands, and this has subsequently been reported in the journal Science. So far mink on 16 farms have been infected, plus 67 out of 98 farm workers have tested positive for SARS CoV2 infection, either by PCR or antibody tests.
The investigators in the Netherlands compared the mink outbreak variants to human isolates, 1775 national and 34 local isolates, and found no exact matches. Although these are new variants, it should be reassuring as it suggests there has only been local transfer from humans to mink and back to humans; there has been no sustained wider transmission of the mink-related variants.
Another reassuring aspect of these outbreaks was that there was no particular variant of SARS CoV2 that predominated, there was a large diversity in the viruses, the number of mutations were small (maximum 12 nucleotide mutations) and the clinical presentation of the human cases was the same as other non-mink related cases.
Meanwhile in Denmark…!
June 2020 – Denmark
From June to November there have been 5 big clusters of SARS CoV2 infection in 200 mink farms, mainly from the North Jutland area of Denmark. Denmark has about 17 million mink in farms for the fur trade (that’s a lot of animals being farmed for their “fashionable” pretty fur).
Within Denmark there has been an ongoing study looking to see if there have been any human cases associated with mink farming. Isolates of viruses from patients across Denmark have been genetically sequenced and compared to those from mink. This has identified 214 cases of Covid-19 in humans associated with mink farms.
The studies done in Denmark have also looked to see if there are any mutations occurring in the SARS CoV2 virus; mutations might have implications for increased infectivity in humans or break through of natural or vaccine induced immunity. This is really important because if the virus is able to mutate in a particular way it might be able to bypass the hosts’ immune system causing recurrent infections or make a promising vaccine ineffective. In a way this is what Influenza Virus does every year, and why we have outbreaks of “Flu” every winter (and why we have a new flu vaccine every year… have you had yours yet?!)
Yep you guessed it, they found mutations! The media and even some scientific papers have called these “new strains of coronavirus”… but hang on!!! They are not. They are all “variants of SARS CoV2”; variants means “slightly different in form or function” (e.g. Cheddar, Wensleydale and Stilton are all variants of hard cheese). Whereas strain means, “a genetic difference… a specific type, quality, or character” (e.g. goats cheese is not cow’s milk cheese, brie is soft cheese, and Roquefort is ewe’s milk). The different strains of “coronaviruses” are SARS, MERS, SARS CoV2; the mink mutations are variants of the SARS CoV2 virus. A new strain is different and has pandemic potential whereas a variant is still the same virus and still “recognisable” as the original virus.
So far Denmark has seen 2 important mutations. One mutation increases the affinity of SARS CoV2 for the host cell’s ACE2 receptor which allows the virus to “enter the cell”. As the ACE2 receptor in mink is slightly different to that of human’s, the virus has mutated to a new variant that then allows it to better access into the mink’s cells. It is thought that this mutation leads to increased ability for SARS CoV2 to spread in mink. When this mutated variant transfers back to human’s it has also been found to be better able to bind to human ACE2 as well, which potentially makes this variant more infectious in humans.
The other variant they found in the Denmark mink has 4 mutations. These particularly mutations affect the spike protein which helps the virus “bind to host cells”. These spike proteins alter the body’s immune response which may not recognise the new variant as these spike proteins are the main target for both natural and vaccine induced antibodies against SARS CoV2. They found that in 9 patients who had previously recovered from Covid-19 this mutation appeared to make the virus 4 times less susceptible to their naturally derived antibodies. This means with another host (the mink) we could see repeated infections from mink to humans and repeated outbreaks due to sporadic reintroductions of “antibody resistant” virus. But I’m not going near mink!? But you never went near a bat either! It only needs one human to acquire the antibody resistant variant SARS CoV2 and spread it for there to be another outbreak. A resistant outbreak could be a big problem. So far 12 human cases of this antibody resistant variant have been identified in people with close contact with mink farming. Fortunately, their disease has followed the same course as the original Covid-19 cases, no better no worse.
At first glance it looks worrying that there are new variants of SARS CoV2 cropping up in animals in Europe but let’s just think about it for a moment. This virus will mutate over time; it’s a natural process. All life mutates eventually; humans are said to have a common ancestor “Lucy” and look how wonderfully genetically diverse we all are now. Viruses just do it faster! I wonder how different a SARS CoV2 isolate from a patient today in Texas would compare to an isolate from a patient in Denmark… if both isolates had a common ancestor in April and the virus mutated at the currently accepted rate of about 1 nucleotide every 2 weeks, the isolates could be 16-20 nucleotides different already… mink coat or Texan Stetson? Take your pick.
Originally the Danish Government wanted to cull all the 17 million mink in mink farms across the country but apparently this is now on hold because the Government do not have the legal right to order this, funny, money has got in the way! In the meantime the outbreak continues….
Why worry about mink?
Okay, so we can worry about mink being infected with SARS CoV2 and this making them sick and causing their suffering. The evidence of spill back from mink into humans is another worry, especially if the virus is undergoing mutation in the mink which might affect its ability to cause disease in humans. This is a good reason to take this seriously, but there is another concern.
What happens if a more common animal becomes infected from mink in mink farms? There will be lots of rodents such as rats and mice that could potentially become infected if the virus becomes modified in a mink host to make it possible to cross another species barrier. This hasn’t happened yet; remember mice can’t get SARS CoV2, but it is theoretically possible. This might then lead to a surge in cases if the source of infection is as common as a mouse… mice don’t physically distance and I’ve never seen one wearing a face mask! We would then be dealing with a zoonotic infection with an uncontrolled host, with bidirectional movement between humans and vector, and this would be a nightmare scenario. Cases of Covid-19 would soar.
But don’t panic, we’re not there yet.
November 2020 – Sweden
Just to bring this even more up to date, this week in the news it was announced that 13 out of 40 mink farms in Sweden now also have cases of SARS CoV2 infection in their animals… watch this space…. Oh, and by the way there are lots of countries which still commercially farm mink; Spain, Italy and the USA to name but a few… and there have already been SARS CoV2 outbreaks at mink farms in Utah and Wisconsin in the USA. Fortunately, fur farming has been banned in the UK since 2000.
In the meantime, Denmark has been added to the travel ban in the UK. Any patients who have returned from Denmark admitted to UK hospitals are to be tested for SARS CoV2 on admission and Day 5. They are to be cared for in negative pressure single occupancy rooms, and if they test positive they are to be transferred to a “specialist infectious diseases centre” by which we assume the Department of Health mean a High Level Isolation Unit (HSIU) but they’re not clear… let’s just hope I’m not on call again when the first case comes through….
Just to bring this even more up to date, this week in the news it was announced that 13 out of 40 mink farms in Sweden now also have cases of SARS CoV2 infection in their animals… watch this space…. Oh, and by the way there are lots of countries which still commercially farm mink; Spain, Italy and the USA to name but a few… and there have already been SARS CoV2 outbreaks at mink farms in Utah and Wisconsin in the USA. Fortunately, fur farming has been banned in the UK since 2000.
In the meantime, Denmark has been added to the travel ban in the UK. Any patients who have returned from Denmark admitted to UK hospitals are to be tested for SARS CoV2 on admission and Day 5. They are to be cared for in negative pressure single occupancy rooms, and if they test positive they are to be transferred to a “specialist infectious diseases centre” by which we assume the Department of Health mean a High Level Isolation Unit (HSIU) but they’re not clear… let’s just hope I’m not on call again when the first case comes through….
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