New developments in Midwestern canine influenza outbreak

New laboratory tests show that a strain of canine influenza virus (CIV) associated with more than 1,000 sick dogs throughout the Midwest, including one dog in Madison, is virtually identical to an Asian strain of the virus and is not a mutated form. A week ago, initial tests at the Wisconsin Veterinary Diagnostic Laboratory (WVDL) and Cornell University identified the strain as H3N2, which has previously only been seen in Asia and is different than the H3N8 strain circulating in North America. Genetic sequencing conducted at the National Veterinary Service Laboratory in Ames, Iowa, now confirms that the H3N2 strain found in the Midwest is almost identical to its Asian counterpart and was likely brought to the United States by an infected animal. "This means there is no evidence of genetic reassortment," says Kathy Toohey-Kurth, virology section head at WVDL. "This is good news because mutations are unpredictable, and we would not necessarily know what the safety implications are for humans or other animals." There is no evidence at this time that the H3N2 CIV strain can infect humans; it is distinctly different from human seasonal influenza H3N2 strains. However, the Asian H3N2 CIV strain has been reported to infect domestic cats. "No cats have reported positive in the United States at this time," says Keith Poulsen, WVDL diagnostic and case outreach and clinical assistant professor at the UW-Madison School of Veterinary Medicine (SVM).