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Within a week, the outbreak had spread to 10 farms and the first reports of mammalian viral adaptions (PB2-E627K) began to emerge (see Preliminary Sequencing Of H5N1 In Fur Farms). In addition to blue foxes, mink and raccoons were also listed as infected.
For the first few weeks, despite international expressions of concern (see PNAS: Mink Farming Poses Risks for Future Viral Pandemics), Finnish authorities declined to order the culling of infected animals. Fur farms are big business in that part of the world, and have a strong lobby.
A little more than a week later (Aug 8th), Finland's Institute for Health and Welfare (THL) released a strong statement urging the Food Authority to take more decisive actions, warning:On August 1st, the food safety authority announced the decision to cull all of the mink housed at 3 H5N1 affected farms, stating that `Decisions to cull other animals will be made on a case-by-case basis'.
Although mink is considered to be the most problematic animal species in terms of avian influenza virus infections, there are also risks associated with bird flu epidemics in dense, large animal populations of foxes and other fur-bearing animals, that the virus becomes more adaptable to mammals.
A week later Ruokavirasto pledged to test all of the fur farms in the country (n > 400), but stated it would take months to complete. Since then, the number of official reported infected farm remains at 26, and we've seen few updates over the past 3 weeks.
Today, more than two months into this crisis, the Food Agency announced the decision to cull all animals on infected farms, regardless of their species, following the detection of worrisome mammalian adaptation in foxes and raccoons.
(translation)
The Food Agency orders all animals to be euthanized from fur farms infected with bird flu
13 September 2023
The Food Agency orders all foxes and raccoons to be euthanized from fur farms that have been found to be infected with bird flu. All minks have already been ordered to be killed from breeding farms. The reason for terminations is to protect people's health.
Sequencing studies have been carried out on avian influenza viruses isolated from fur farms, in which the virus's genome and the changes occurring in it are investigated. Sequence analysis supports the indications that the viruses have also spread from fur animals to other fur animals in animal shelters, not only from birds to fur animals. In addition to droplet infection, infection from animal to animal can occur as a contact infection via animal secretions (especially saliva), feed or contaminated bedding and care equipment. It is not necessarily possible to find out the route of infection after the fact.
The longer viruses can circulate in mammals, the greater the risk of mutations that can cause infections in humans as well. So far, worrisome mutations that facilitate the transmission of the virus to a mammal have been identified in the genome of six viruses isolated from fur farm animals. Mutations have been found in minks, foxes and raccoons. Research on virus strains in fur farms continues in cooperation with the EU bird flu reference laboratory.
The symptoms of animals infected with bird flu can vary from severe to very mild, and the infection can also be asymptomatic in animals. This is why it is important to start inspections also in fur farms where no symptomatic animals have been found. In fur farms infected with avian flu, demonstrating freedom from infection with sufficient certainty would require taking such a large number of samples from the fur farm that it is not practically possible to do so. Latent infections in asymptomatic animals would cause an occupational health and safety risk for workers during skinning, and the risk of infection to humans would continue even after the skinning season.
The Food Agency's new cull decisions concern approximately 115,000 animals, of which 109,000 are foxes and 6,000 raccoons. In addition, the Food Agency has previously ordered the cull of approximately 135,000 animals, of which 50,000 are minks, 79,000 foxes, and 6,000 raccoons. at a fur farm in Ostrobothnia. Of these 11 shelters, all the animals have been ordered to be euthanized so far, and some of the animals from five shelters. In addition, 10 shelters have not yet been closed down. Now all the remaining animals in these shelters are ordered to be euthanized.
Termination decisions concerning foxes and raccoons were previously made on the basis of a case-by-case assessment. The evaluation was influenced by how widely and with how strong the symptoms of infection have been found at the shelter.
More information:
Head of department Terhi Laaksonen, tel. 029 520 4530 (animal disease control)
Research professor Tuija Gadd, tel. 029 520 4183 (virological studies)
E-mails: firstname.surname@ruokavirasto.fi
The concern, particularly with high density animal farms, is that it provides the virus with an ideal environment to spread from mammal to mammal. Long chains of infection (see graphic below) can provide the virus with additional opportunities to adapt to a new host species, furthering its evolution.
While fur farms aren't the only place where these conditions exist (see Study: Seroconversion of a Swine Herd in a Free-Range Rural Multi-Species Farm against HPAI H5N1 2.3.4.4b Clade Virus), mink (along with foxes and raccoons) are particularly susceptible to influenza A viruses and they are usually raised in extremely close quarters facilitating transmission.
We aren't getting daily updates on their testing progress, but with more than 400 fur farms to test, they've probably only sampled a small fraction of the susceptible population.
And even if a farm tests clean today, that doesn't prevent the virus from gaining entry tomorrow. With rising levels of H5N1 in the environment - even with better biosecurity - fur farms make for excellent flu factories.
