Netherlands: COVID-19 In Farmed Mink

#15.224

Almost four weeks ago, in Susceptibility of Ferrets, Cats, Dogs & Other Domestic Animals to SARS-CoV-2, we looked at the experimental infection of a variety of farmed animals and household pets with the novel coronavirus.  The authors wrote:

We found that SARS-CoV-2 replicates poorly in dogs, pigs, chickens, and ducks, but efficiently in ferrets and cats. We found that the virus transmits in cats via respiratory droplets.

Given their similarity to ferrets - and since we've seen mink, and mink farms, infected with a variety of novel flu viruses over the past couple of decades - in the postscript I wrote:

Another species I would have liked to have seen included in this study are mink. They are extensively farmed in China - and around the world - and like ferrets, are highly susceptible to a number of human viral respiratory infections. A few of many studies we've looked at include:

Nature: Semiaquatic Mammals As Intermediate Hosts For Avian Influenza

That Touch Of Mink Flu (H9N2 Edition)

Vet. MicroB.: Eurasian Avian-Like Swine Influenza A (H1N1) Virus from Mink in China

Earlier this week, the Netherlands' National Institute for Public Health - RIVM, released the following (translated) statement 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 the primary risk of contracting the virus is (by far) from another person, the RIVM has recommended some stringent measures (closing the roads to cyclists and pedestrians within 400 meters of the farms, testing air samples, etc.) out of an abundance of caution. 

First their report, then I'll return with more.

COVID-19 detected on two mink farms

News item | 04/26/2020 | 11:17

Two mink farms in Gemert-Bakel and Laarbeek have detected contaminations of COVID-19 in different minks. The minks showed various symptoms including respiratory problems. Investigations have been launched to determine the source of the infections. Because some employees had symptoms of the coronavirus at both companies, it is assumed that people are infected with animals. Previous research shows that ferrets, and therefore also minks, are susceptible to COVID-19 contamination. There are currently no indications that farm animals or pets play a role in the spread of COVID-19.

Minister Schouten of Agriculture, Nature and Food Quality has immediately announced measures. As of today, a reporting obligation has been introduced for mink farmers, veterinarians and persons in research institutions. If there are respiratory problems and increased mortality in minks, this must be reported to the NVWA. To prevent possible spread of the virus to other farms, both animals and manure must not leave an infected farm. Since other animals in livestock farming do not appear to be susceptible to the virus, a notification requirement is now only imposed for minks.

Contamination from person to person

It is important to know how the disease develops on the infected farms. This knowledge can be used to better understand the disease and its course in animals and humans.

Therefore, samples are collected from sick and healthy animals. These will be used for further investigation. While it is not expected that the virus will spread over longer distances, air and dust samples are also taken in the vicinity of the company as a precaution. These are being examined to see whether virus can be detected in this. The Lower House will be informed as soon as more information is available about the outcome of this investigation.

According to RIVM, based on current knowledge about COVID-19, the mink companies do not pose a risk of further spread to humans. Human to animal contamination is possible, but the impact of this mink contamination on human health is currently negligible. Human to human contamination is the driving force behind the current corona pandemic.

Precaution

There is currently no reason to believe that the virus spreads in these mink farms in any other way than it does between humans. As a precautionary measure, RIVM advises against cycling or walking within a radius of approximately 400 meters around the infected mink farm until the results of the research on the air and dust samples are known. It was decided to close the public road in this radius around the company for pedestrians and cyclists until the results of the research are known. The mayors of both municipalities will soon take this measure.

Documents

Letter to parliament Infection of minks with SARS-CoV-2

Letter to the Lower House of Minister Schouten (LNV) about mink infection with SARS-CoV-2.

Parliamentary Paper: Letter to Parliament | 04/26/2020

Although medium distance transmission (from hundreds of yards to a few km) of the virus is considered unlikely, we have seen past evidence of `viral plumes' emanating from avian flu infected poultry farms, with the virus carried on tiny dust particles (desiccated chicken manure, feathers, etc.) propelled aloft by exhaust fans.

• In 2019, we saw a report suggesting that long-distance airborne transmission may have been a factor in the spread of avian flu among Iowa's farms in the spring of 2015 (see Nature: Airborne Transmission May Have Played A Role In Spread Of U.S. 2015 HPAI Epizootic).

• In 2018, in Frontiers: Two Studies On The Epidemiology of Avian Influenza Viruses, we looked at a study that detected airborne HPAI viruses during the 2016-17 H5N8 epizootic in France, which saw more than 400 farms affected.  

• In 2012's Barnstorming Avian Flu Viruses? we looked at a study in the Journal of Infectious Diseases called Genetic data provide evidence for wind-mediated transmission of highly pathogenic avian influenza that found patterns that suggested farm-to-farm spread of the 2003 H7N7 in the Netherlands due to the prevailing wind.

• Another study of the same outbreak, Modelling the Wind-Borne Spread of Highly Pathogenic Avian Influenza Virus between Farms (PloS One 2012), found that wind borne transmission could have accounted for up to 24% of the transmission over distances up to 25 km.

• And lastly, to these studies we can numerous anecdotal reports of people living near, or walking past, live poultry markets in China contracting avian flu without direct contact with birds (see J. Infection: Aerosolized H5N6 At A Chinese LBM (Live Bird Market)).

Despite the low risks of seeing the same thing with these two mink farms, when dealing with a novel virus, it is alway prudent to cover all of the bases.

While SARS-CoV-2 susceptible mink pose far less of a concern than if the virus had an affinity for pigs, or poultry, or companion animals - it is important to monitor other potential hosts for the virus - as they could provide additional opportunities for the virus to adapt and evolve outside of our view.

The last thing we want is to be blindsided by this virus a second time.