Dutch officials have begun culling mink from farms that have been linked to SARS-CoV-2 outbreaks after a number of employees and animals have tested positive for the virus, in an effort to ensure that mink farms do not become “virus reservoirs” and a threat to public health.

Culling is expected to be completed within a week, though it is not clear how many animals will be impacted. The measure has been declared an “effective measure for infected farms” after infected mink was first reported on April 26. In late May, Dutch officials began investigating a case where a human may have been infected with Covid-19 from a mink. Most recent figures have found evidence of coronavirus-infected minks from seven farms at nine locations. The government adds that it appears the virus can circulate on mink farms for a long time, presenting a risk to both human and animal health. Research conducted by the Dutch government found that there appears to have been transmission from mink to human, and that mink infections can be asymptomatic.

Early warning testing has since identified new outbreaks and more are expected to be confirmed in the weeks ahead, wrote the ministers for Health, Welfare, and Sport and Agriculture, Nature, and Food Quality in a letter to parliament.

Earlier this month, the government introduced a transport ban and ban on admitting visitors to mink sheds after determining that the risk of the virus being transmitted from minks to humans outside of the sheds remain “negligible,” according to a government announcement. Officials add that mink kits are born in the spring and though previously infected mothers pass antibodies to their kits, maternal immunity decreases over time which may result in five to six times as many susceptible animals on the farm as when the outbreak first began.

The Animal Welfare Committee is overseeing to ensure that the animals are killed humanely and farmers are entitled to compensation and mental health resources if they so need it. The government is also considering a voluntary option for farmers who want to end their farming practice in advance of the 2024 mink farming ban. Farms that wish to remain in operation and have not seen infections are required to have a “lengthy period of isolation” and strict hygiene protocols. Officials are also addressing expanding testing to farm works.

In rare situations, pets around the world have also contracted SARS-CoV-2 but experts argue that the risk of reverse transmission remains low. Both dogs and cats – including several lions and tigers at a New York zoo – have become infected with the virus and spread it to other felines.