What was assumed to be caused by influenza A (H3N8) virus by just about everyone, including the Centers for Disease Control and Prevention (CDC), the canine influenza outbreak in the Midwest has turned out to be something quite different, according to researchers from Cornell University and the University of Wisconsin.
Laboratory scientists say, after additional testing, the outbreak is being caused by a virus closely related to Asian strains of influenza A H3N2 viruses, currently in wide circulation in southern Chinese and South Korean dog populations since being identified in 2006.
The outbreak in the Midwest had been attributed to the H3N8 strain of virus, which was identified in the U.S. dog population in 2004 and has been circulating since. The H3N2 virus had not been previously detected in North America. The outbreak in Chicago suggests a recent introduction of the H3N2 virus from Asia.
H3N2 has caused infection and respiratory illness in cats. There is no evidence that it can be transmitted to humans.
Veterinary professionals are advised that diagnostic testing of samples from sick pets can be done using a broadly targeted Influenza A matrix reverse transciptase-polymerase chain reaction assay (Rt-PCR). The canine-specific Influenza A H3N8 Rt-PCR in use in several laboratories will not detect this virus. Serology is also currently not available as the H3N2 virus is different enough from H3N8 that antibodies may not cross react. However, an H3N2-specific serologic assay is under development and will be available soon, Cornell researchers note.
It is not known if the current vaccine will provide any protection from this new virus. It does protect against H3N8, which is in circulation in some areas. Other preventive advice remains the same: In areas where the viruses are active, avoid places where dogs congregate, such as dog parks and grooming salons.
Owners of symptomatic dogs and cats should consult their veterinarians about testing and treatment.