Canine Influenza Virus (CIV)

As early as the 1920s influenza was shown to be caused by a virus. There are however, three genetically very distinct types of influenza viruses: Influenza A Virus: This is by far the most pathogenic type and is responsible for pandemics such as the Spanish flu outbreak in 1918, Asian flu in 1957, Hong Kong flu in 1968 and the Swine flu in 2009 that was caused by the mysterious re-emergence of a 1918-like virus. Influenza A viruses infect several species including birds, pigs, horses, humans and now unfortunately dogs. There are many serotypes of the virus that are classified based on antibody reactivity to two proteins present on the surface of each virus particle – hemagglutinin (H) and neuraminidase (N). To date 16 different H and 9 N molecules have been identified. Interestingly, all H and N serotypes are found in wild aquatic birds which are therefore believed to be the natural host for influenza A and act as reservoirs for the transmission to other species. However, transmission from an intestinal virus of birds growing at 42oC to an upper respiratory tract infection of mammals where the temperature is approximately 33oC requires the virus to undergo many complex, incompletely genetic changes.