ABSTRACT
Highly pathogenic avian influenza (HPAI) has caused widespread mortality in both wild and domestic birds in Europe 2020-2023. In July 2023, HPAI A(H5N1) was detected on 27 fur farms in Finland. In total, infections in silver and blue foxes, American minks and raccoon dogs were confirmed by RT-PCR. The pathological findings in the animals include widespread inflammatory lesions in the lungs, brain and liver, indicating efficient systemic dissemination of the virus. Phylogenetic analysis of Finnish A(H5N1) strains from fur animals and wild birds has identified three clusters (Finland I-III), and molecular analyses revealed emergence of mutations known to facilitate viral adaptation to mammals in the PB2 and NA proteins. Findings of avian influenza in fur animals were spatially and temporally connected with mass mortalities in wild birds. The mechanisms of virus transmission within and between farms have not been conclusively identified, but several different routes relating to limited biosecurity on the farms are implicated. The outbreak was managed in close collaboration between animal and human health authorities to mitigate and monitor the impact for both animal and human health.
Subject(s)
Animals, Wild , Charadriiformes , Disease Outbreaks , Influenza A Virus, H5N1 Subtype , Influenza in Birds , Phylogeny , Animals , Influenza in Birds/virology , Influenza in Birds/epidemiology , Finland/epidemiology , Influenza A Virus, H5N1 Subtype/genetics , Influenza A Virus, H5N1 Subtype/pathogenicity , Influenza A Virus, H5N1 Subtype/isolation & purification , Animals, Wild/virology , Charadriiformes/virology , Disease Outbreaks/veterinary , Farms , Orthomyxoviridae Infections/veterinary , Orthomyxoviridae Infections/virology , Orthomyxoviridae Infections/mortality , Orthomyxoviridae Infections/epidemiology , Foxes/virology , Birds/virology , Mink/virologyABSTRACT
Since mid-July 2023, an outbreak caused by highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b genotype BB is ongoing among farmed animals in South and Central Ostrobothnia, Finland. Infections in foxes, American minks and raccoon dogs have been confirmed on 20 farms. Genetic analysis suggests introductions from wild birds scavenging for food in farm areas. Investigations point to direct transmission between animals. While no human infections have been detected, control measures are being implemented to limit spread and human exposure.
