Canine Influenza can be caused by two different virus strains H3N8 and H3N2. H3N8 was discovered in Florida in 2004 and can also be found in horses. H3N2 was first identified in Chicago in 2015 and can affect other species such as pigs and birds.
Both viruses are very contagious among dogs and are spread through saliva and respiratory secretions. Nose to nose contact between dogs is an excellent way for the virus to spread. It can also be spread through sharing blankets, toys, dishes and grooming tools. Owners can spread the virus with their hands by petting a sick dog then touching their own dog.
Symptoms of canine influenza include coughing, runny nose and eyes. Sometimes infected dogs will also be lethargic with a decreased appetite. Most cases are mild with the cough resolving within a couple of weeks. Influenza causes death in very few dogs, approximately 1-5% of those infected. Pneumonia may develop in dogs with pre-existing heart or lung disease, elderly dogs or those with a compromised immune system.
Once exposed to the virus symptoms will develop in 2-4 days. It is during this incubation period that animals are most contagious which allows for rapid spread of the virus as it is not known yet that the dog is sick. Infected dogs can continue to shed the virus for up to 20 days.
Treatment is mainly supportive with rest and ensuring the patient is eating good quality food and drinking water. Sometimes antibiotics may be prescribed to treat secondary bacterial infection. If pneumonia develops chest x-rays and blood work are required as well as hospitalization and broad spectrum antibiotic therapy.
Canine Influenza can be diagnosed with PCR if a nasal swab is taken within the first few days of onset of clinical signs as this is when the virus load is the highest. After this period antibody levels must be measured for accurate results. Two samples are taken 2-3 weeks apart, a significant rise in antibody levels indicates active infection.
An influenza vaccine is available, but like the human flu shot it is not 100% protective. Dogs who are vaccinated should have milder symptoms for a shorter period of time and would be less likely to develop pneumonia. Vaccination could be considered if you live or plan to travel with your dog to an area where canine flu is known to exist, if you take your dog to dog shows, dog parks or doggy daycare. Dogs with heart or lung disease may also benefit from vaccination.
At this time canine influenza is not known to cause any disease in humans.
Written by: Dr. Dana Cini, DVM