Canine influenza, also known as dog flu, is a highly contagious respiratory disease affecting dogs. It is a Type A influenza virus. Two different strains of canine influenza virus have been identified thus far: an H3N8 virus and an H3N2 virus.
Influenza viruses are constantly changing and giving rise to new strains that can infect different species. Both strains of canine influenza which have been identified can be traced back to influenza strains known to infect species other than dogs, and at some point, these viruses acquired the ability to infect dogs and to be transmitted from dog to dog.
Canine influenza H3N8 viruses originated in horses. H3N8 equine influenza (horse flu) viruses have been known to exist in horses for more than 40 years, and there is now a dog-specific, or canine, H3N8 virus. Canine H3N8 influenza was first identified in the US in 2004 in racing greyhounds and has since been detected in dogs across other regions.
Canine influenza H3N2 viruses originated in birds. Canine influenza A H3N2 viruses were first detected in dogs in South Korea in 2007 and have also been reported in dogs in China, Thailand and Canada. It is thought that the virus likely arose through the direct transfer of an avian influenza virus (possibly from among viruses circulating in live bird markets) to dogs. Canine H3N2 influenza was first identified in the US in 2015 and the H3N2 canine viruses reported in the US have been almost genetically identical to canine H3N2 viruses previously reported only in Asia.
Transmission of H3N2 canine influenza viruses from infected dogs to cats has also been reported.
At this time there is no evidence that canine influenza affects humans, nor that it has pandemic potential.
Canine influenza is transmitted among dogs through respiratory droplets produced during coughing, barking and sneezing from infected dogs, or through contact with contaminated surfaces. Dogs in close contact with infected dogs (such as at kennels, groomers, shelters etc) are at increased risk of infection.
Canine influenza can also be spread indirectly through people who have been in contact with infected dogs, and via contaminated objects such as food and water bowls, collars, leashes and bedding. It is therefore important to clean and disinfect objects that have been in contact with an infected dog, and to separate infected dogs from other pets in the home or shelter.
Signs of canine influenza in dogs include cough, runny nose, fever, lethargy, eye discharge and decreased appetite, but not all dogs will show symptoms. Most dogs recover within two to three weeks, but some dogs may develop secondary bacterial infections which may lead to pneumonia and sometimes death.
Treatment consists of supportive care including keeping the dog hydrated and comfortable. Broad-spectrum antibiotics may be prescribed by your veterinarian if a secondary bacterial infection develops. Vaccines to protect dogs against both H3N8 and H3N2 canine flu are available. Your veterinarian can provide additional information about these vaccines and whether you should consider vaccinating your dog.
Copyright © Kristel-Marie Ramnath 2023