Influenza on Dutch mink farms in 2011

Abstract

In the middle of May 2011 three farms in the Netherlands claimed increase of mortality of the young pups round the age of 15 days old. The three farms were scattered over The Netherlands. Employees of the diseased farms even as the farmer and his family were suffering from influenza like symptoms. The pups at the 3 farms feel bad and show pumping breath like the acute form of plasmacytosis. The mortality of the pups at the 3 farms run from 11% to 30%. The lungs of the pups at the obduction were very red and were sinking in water. Histological research prove that the pups had an acute interstitial pneumonitis, perhaps caused by a viral infection. Bacteria were not found. Immunohistochemical stains for influenza type A were positive in the lungs of these pups. The PCR influenza A H1N1 was positive in all three cases. In the ELISA test for influenza antibodies from blood samples of ad random chosen adult females at the diseased farms run from 21.8% to 97.3% positives. The ELISA test demonstrated that 72% of 25 selected farms scored positive in this test. The positive females run from 2.7% to 97.3%. Sixty percent of these farms had no clinical symptoms with the pups. Retesting in August of 25 females who lost one or more pups at the diseased farms, demonstrated that mothers were 64% to 96% positive reactors in the ELISA test. Positive reacting pups in the ELISA test were running from 6% to 12%. Till this moment it is not yet clear where the infection at the stroked farm came from and why the farms with minks with positive Elisa for influenza had no clinical problems.