Naturally occurring Influenza A virus subtype H1N2 infection in a Midwest United States mink (Mustela vison) ranch


Influenza A virus (FLUAV) causes acute respiratory disease in humans and a variety of animal species. The virus
tends to remain within the species of origin; nonetheless, naturally occurring cross-species transmission of FLUAV has been
periodically documented. Multiple cross-species transmissions of FLUAV have been reported from companion animals and
captive wild animals, neither of which is historically considered as natural hosts of FLUAV. In the fall of 2010, mink (Mustela
vison) inhabiting a 15,000-head mink farm in the Midwest United States experienced persistent severe respiratory distress and
nose and/or mouth bleeding. Mink losses averaged approximately 10 animals per day. Six dead mink at 6 months of age were
submitted to the Iowa State University Veterinary Diagnostic Laboratory for diagnostic investigation. Gross and microscopic
examinations revealed that all 6 mink had hemorrhagic bronchointerstitial pneumonia. Hemolytic Escherichia coli was isolated
from lungs, probably accounting for hemorrhagic pneumonia. All animals tested negative for Canine distemper virus and
Aleutian mink disease virus. Interestingly, FLUAV of H1N2 subtype, which contained the matrix gene of swine lineage, was
detected in the lungs. Serological follow-up on mink that remained in the ranch until pelting also confirmed that the ranch had
been exposed to FLUAV of H1 subtype (δ clade). The case study suggests that FLUAV should be included in the differential
diagnosis when mink experience epidemics of respiratory disease. Since the source of FLUAV appeared to be uncooked turkey
meat, feeding animals fully cooked ration should be considered as a preventive measure.