Canine influenza or dog flu was first identified in early 2005 after the outbreak of an epidemic of a dog respiratory system disease in the greyhound racetracks in Florida. A major outbreak of the disease was next reported in New York State, and by 2006 it had spread to 22 states of the USA and was believed to affect almost 16% of the dogs, with a mortality rate of 7%.
The canine influenza virus (CIV) belongs to the same family as the equine influenza virus, which has been around since the last forty years. It is understood that the contagion occurred on the same racing tracks used for greyhound as well as horse racing.
When inflicted with canine influenza, almost 80% of the dogs show mild symptoms, and the other 20%, although infected, do not show any visible symptoms.
Mild dog flu manifests as cough that may last for up to a month and is often accompanied by a greenish discharge from the dog nose. Severe manifestation of the disease is characterized by high fever and pneumonia. The pneumonia, however, is not caused by CIV, but is a secondary infection caused by bacteria. Without proper treatment, pneumonia in such cases leads to hemorrhagic pneumonia, and an inflammation of blood vessels proves to be fatal in almost 50% of the instances.
Any infection of the canine respiratory system, especially in dogs that have been vaccinated against kennel cough, should be first checked for canine flu. This is more important in areas that have earlier reported instances of canine influenza. Although laboratory tests of a serum sample can help in confirming the prevalence of CIV, the confirmation on its own does not make any significant difference to the treatment, since there is no drug available to lessen the duration of the disease.
Antibiotics are ineffective against viruses, and this holds true for the canine influenza virus, also. In most dogs, symptoms of canine flu disappear over time, and only supportive and preventive treatment is required. Suspected cases, however, should always be evaluated for prevalence of any signs of pneumonia.
Dogs do not have a natural immunity to CIV because of a lack of previous exposure. Canine flu is a contagious disease and it is almost certain to infect once a dog has been exposed to it. Once having contacted the virus, dogs normally attain immunity for almost one year.Sources