Utah mink found near infected fur farm confirmed as first known Covid-19 case in a wild animal
The US Department of Agriculture (USDA) has confirmed the first known case of the coronavirus in a wild animal, a mink. In an alert to the International Society for Infectious Diseases, US officials said a wild mink had tested positive around an infected mink farm in Utah during the screening of wildlife around fur farms with outbreaks.
Farmed mink are known to be susceptible to the virus, with cases reported at fur farms in the US and Europe. But this is the first known detection of the coronavirus in a “free-ranging wild mink.” It is unclear how the wild mink may have come into contact with infected mink on a farm.
“The USDA National Veterinary Services Laboratories (NVSL) has confirmed SARS-CoV-2 (the virus that causes Covid-19) by real-time RT-PCR and sequencing of a nasal swab collected from a free-ranging, wild mink sampled in Utah. To our knowledge, this is the first free-ranging, native wild animal confirmed with SARS-CoV-2. APHIS (Animal and Plant Health Inspection Service) has notified the World Organisation for Animal Health (OIE) of this detection in a wild mink as part of the epidemiological study in the surrounding area of the infected farm,” read a statement. It added, “The USDA ASPIS conducted wildlife surveillance for SARS-CoV-2 in meso-carnivores and other species around infected mink farms in Utah, Michigan, and Wisconsin, between August 24-October 30, 2020. Surveillance was conducted as part of “one health” investigations involving the Centers for Disease Control and Prevention (CDC), the United States Geological Survey (USGS), and State Departments of Agriculture, Natural Resources, and Health.”
There is currently no evidence that Covid-19 is circulating or has been established in wild populations surrounding the infected mink farms. Several animals from different wildlife species were sampled, but all others tested negative, noted officials. “The sequence of the viral genome obtained from the wild mink sample at NVSL was indistinguishable from those obtained from the farmed mink,” they explained.
Thomas DeLiberto and Susan Shriner from USDA-ASPIS explained that the American mink is a “semiaquatic species of mustelid,” native to North America. “The high susceptibility of this mustelid species to SARS-CoV-2 has become apparent in mink farming countries; most outbreaks reported so far are from Denmark, Netherlands, and the US. This susceptibility has also been demonstrated experimentally. Though escapees from fur farms are known to have become self-sustaining in some countries, so far, no Covid-19 cases have been reported from such animals,” they added.
The USDA has recommended that to prevent the potential establishment of a “virus reservoir,” efforts to prevent coronavirus introduction into and spread within the large North American wild mink population, as well as elsewhere, are warranted.
Since June 2020, Danish authorities have reported an extensive spread of SARS-CoV-2 on mink farms in Denmark. Global health experts are investigating the potential risk the animals may pose to people after Denmark decided to cull its farmed mink population of 17 million.
“On 4 November 2020, Denmark decided to cull all farmed mink in Denmark. This decision was made following information that it had not been possible to prevent the spread of infection from farm to farm, or from animals to humans, and mink are acting as a reservoir and contributing to the ongoing transmission in Denmark,” stated the World Health Organization (WHO). It added, “By November 25, mink on all 289 affected mink farms, and farms within an assigned zone, were culled. Additionally, mink farming has been banned in Denmark until December 31, 2021, including import and export of live mink.”
Mink have previously been reported to be infected with SARS-CoV-2, including in two outbreaks on large mink farms in the Netherlands in April 2020. Additionally, the Netherlands have reported human infections with mink-associated SARS-CoV-2 strains. To date, eight countries, namely Denmark, Lithuania, Netherlands, Spain, Sweden, Italy, and Greece, and the US have reported coronavirus in farmed mink to the World Organisation for Animal Health (OIE).
In its risk assessment, the WHO stated it is expected that all viruses, including SARS-CoV-2 change over time. It noted that while public health and social measures implemented by Denmark have led to positive developments, recent findings of other mink-associated variants among human cases in mid-Jutland and the detection of some 200 human cases among workers are of concern.
“SARS-CoV-2 strains, which are infecting mink and subsequently transmitted back to humans, may have acquired unique mutations to adapt to the mink host. Advanced laboratory studies are required to fully understand the impact of novel variants of SARS-CoV-2 on viral properties such as transmissibility, clinical presentation, and effectiveness of diagnostics, therapeutics, and vaccines. These studies are long, complex, and are done in close collaboration with various research groups,” said the agency on December 3.