In late April - in Netherlands: COVID-19 In Farmed Mink - we looked at preliminary reports released by the Netherlands' National Institute for Public Health - RIVM, on the detection of SARS-CoV-2 at two mink farms - located roughly 5 km apart - in the south-central part of the country.
While SARS-CoV-2 has already established itself in humans, the concern is - should SARS-CoV-2 find other suitable animal reservoirs - it could make it much harder to control, and could conceivably even provide the virus with additional opportunities to evolve and adapt to mammalian hosts.
Over the summer we'd see hundreds of mink farms affected in The Netherlands, Denmark, Spain, and even the United States (see USDA APHIS Confirms SARS-CoV-2 in Farmed Mink in Utah), and even some evidence suggesting mink-to-human transmission may have occurred (see COVID-19: Back To The Mink Farm).
Details remain limited, although it appears that this mutated virus has already been detected in humans. We have a couple of (translated) announcements from the Danish government, which appears to be taking these developments quite seriously.
Our first stop is this statement from the Danish Veterinary and Food Administration.
All mink must be killed as a result of COVID-19
The Statens Serum Institut has found a mutated form of corona virus in mink. It poses such a serious danger to public health that the government has decided that all mink in Denmark must be killed. (Article published by coronasmitte.dk) News , Published: November 4, 2020
The mutated form of the virus that Statens Serum Institut has found, showed reduced sensitivity to antibodies and it is a variant of the virus that can migrate from mink to humans. There is a risk that a future vaccine will not have an effect on the mutated form of virus.
And there is a risk that the mutated form of virus could spread to other countries.
Therefore, the government has decided that it is necessary to kill all mink in Denmark, including the breeding animals, even though it is a serious decision for the country's mink farmers. At the same time, the authorities will announce a number of additional restrictions tomorrow, which will apply to the population in a number of municipalities in North Jutland and Himmerland.
The Government has therefore decided that the situation is now so serious that both the infected herds and the herds in the immediate vicinity of the infected herds must be killed.
Efforts to kill mink throughout the country will be coordinated through the National Operating Staff (NOST). The police and the Armed Forces, together with the Danish Veterinary and Food Administration, will intensify the killing of the animals.
Mink breeders who kill their animals themselves will receive increased compensation.
November 3, 2020MFVM has requested SUM for a risk assessment in relation to human health, if mink breeders follow killing of infected animals or fur in the 2020 season, mink production will continue into 2021 as normal. Only an assessment of risk is needed, not suggestions for possible solutions.
As of 2 November 2020, SARS-CoV-2 infection has been found on 191 mink farms. This development has taken place despite intensive efforts by the authorities with regard to to limit infection.
At the same time, infection is seen with new types of SARS-CoV-2 virus that adapts to mink (mink variants) in the local population, and there is a strong geographical and temporal correlation between numbers positive mink farms and the incidence of infection among humans.
Mink with SARS-CoV-2 makes a great reservoir of viruses, which is a major occupational risk associated with mink breeding in infected areas, and it has not succeeded in limiting further spread to the surrounding community.
Because of the changes that occur in the spike protein in several of the mink variants of the virus, there is a risk that vaccines targeting the spike protein will not provide optimal protection against the new viruses, occurring in mink, and the immunity from past COVID-19 infection may provide less protection against the new virus variants.
If mink production continues in Denmark, so that in 2021 a large one will be re-established population of mink, it is considered highly probable that this population will be susceptible to infection. In addition, SARS-CoV-2 is still expected to be in circulation among people and no significant immunity in the population until the majority of the population is vaccinated.
Thus, there is a significant risk of recurrence of infection among mink and people who have been seen in Western Denmark in 2020. This is considered to involve a great risk for public health, both by causing greater disease burden among humans, and by a large virus reservoir in mink increases the risk of recurrence of new virus mutations, which vaccines do not provides optimal protection against.
Overall, the herd immunity obtained by vaccination or past infection, risk of being weakened or absent. At the same time, it must be expected to mean a significant deterioration of our opportunities to maintain epidemic control in Denmark, which can entail that one must introduce further restrictions and limitations on community life, etc.
Conclusion: A continued mink breeding during an ongoing COVID-19 epidemic involves one significant risk to public health, including the possibilities for preventing COVID-19 with vaccines.
This risk assessment goes on to describe the mutations to COVID-19's spike protein.
Virus mutations are small changes in virus genetic material that occur continuously in connection with that virus copies itself. The more viruses that are copied, the more likely they are to occur mutations. A virus's genetic material, and thus any mutations, can be uncovered by whole genome sequencing (WGS). Several mink variants of SARS-CoV-2 have been seen examples of changes in the spike protein. The spike protein is essential, taking humans after one natural infection forms antibodies to the spike protein, and the potential COVID-19 vaccine candidates are also based on this protein. Therefore, there is a risk that the effect of spike-based anti-COVID19 vaccines may be affected when changes occur in this part of the genetic material.
The presence of an extensive reservoir of virus in mink poses a serious threat to public health, as viruses spread from animals to humans. The risk of mutations makes this risk particularly serious. Mutations in the spike protein also occur in viruses in humans worldwide) unrelated to mink farms, but not or very rarely the same mutations which occurs in mink. However, it has been shown that the current vaccine candidates will be able to cover them variations of viruses that have emerged among humans over the spring.
Concerns about changes in the spike protein in mink variants of SARS-CoV-2 were raised by the State Serum Institute when the first mutations were detected. Among the mink varieties, seven have been seen different mutations in the Spike protein and examples of up to 4 different changes in Spike the protein in the same virus. A specific virus with 4 changes in the genes for spike protein has been detected in five North Jutland mink farms and in 12 patient samples, of which 4 with direct connection to three of these farm (cluster 5).
Preliminary studies suggest that this virus exhibits decreased susceptibility to neutralizing antibodies from several people with a history of infection. This is proven in a laboratory experiments, where it is seen that the particular mink virus is not inhibited to the same extent in the growth of antibodies from humans that have been infected with a non-mink-related variant of SARS-CoV2. Ongoing studies will further uncover the issue. Additional variants are identified by sequencing but not yet investigated for neutralization.
This is worrying, as it could potentially affect the efficacy of a future COVID-19 vaccine against infection with new mink variants, and involve a risk of impaired immunity to these after over COVID-19 infection, which is important for the individual and for herd immunity in society.
What is clear is the Danish government is taking these developments seriously.
We should learn a good deal more about the scope and extent of the threat posed by these recently detected COVID-19 variants in the days to come.