History

The presence of an influenza virus capable of transmission from dog to dog was first identified in January 2004 in a population of racing greyhounds acutely afflicted with respiratory disease at a racetrack in Florida. Eight of the 22 infected dogs died from pulmonary hemorrhage. An H3N8 influenza virus was subsequently identified as the cause. Canine influenza virus (CIV) has now been documented in 30 states. As infected dogs travel the country the virus is expected to spread.

The Virus

The CIV (H3N8) subtype has not been found to be contagious to humans or cats. Unlike human flu viruses, there has been no evidence that new new strains of the CIV are developing annually.

Shedding of the virus by an infected dog begins before the clinical signs are noted and, on  average, will last 5 days. The virus is is spread by aerosol transmission of respiratory secretions via sneezing or coughing. Direct contact with the respiratory secretions or contact with freshly contaminated surfaces will also serve as a source of exposure.

Clinical Signs

Being a relatively new virus, most dogs have never been exposed to CIV. They therefore lack a natural or aquired (from previous exposure or vaccination) immunity to protect them from the virus. Consequently, most dogs exposed to the virus are likely to develop clinical signs of infection.

Signs of CIV infection typically develop within 2-3 days of virus exposure. The clinical signs of CIV infection are similar but may be more severe to those of 'kennel cough'. Lethargy, anorexia, nasal discharge, low grade fever and a persistant, dry non-productive cough are common clinical manifestions of the illness. Some dogs may develop pneumonia. The presence of secondary bacterial infections can exacerbate the severity of the illness. Cases of severe pneumonia, pulmonary hemorrhage, and death, which were noted in early outbreaks of the disease, appear to be uncommon in the pet population. Signs can persist for weeks.


Treatment

Treatment is supportive in nature, similar to treatment for 'kennel cough'.

Prevention

In May 2009 the USDA  approved a killed adjuvanted whole virus vaccine produced by Intervet. A field trial performed in 700 vaccinated dogs failed to demonstrate any side effects. Efficacy trials have demonstrated the vaccine to significantly reduce the severity and duration of clinical signs of illness and reduce the amount of and duration of virus shedding (i.e. degree and period of  contagiousness). The vaccine will not prevent infection. Vaccinated dogs may still show mild clinical signs.