An outbreak of the highly contagious Canine Influenza Virus began in April 2023 when an infected dog brought in from Oklahoma to a Golden Valley, Minnesota Humane Society and promptly infected of of its occupants. The cases total is now up to 300, but since these are only confirmed cases via testing, that number is likely much higher. In an age where it is increasingly commonplace to travel with their dogs, there are growing concerns of a potential nationwide outbreak and calls to have dog immunized against the virus with the two strain (H3N8, H3N2) vaccine.
My home state of Florida was the ground zero of the first records Canine Influenza outbreak in 2004 with H3N8 first identified in racing greyhounds. The next major outbreak was H3N2 in Chicago and there have been smaller outbreaks of each strain across the country since. The current Minnesota outbreak is H3N2.
Canine influenza is transmitted through droplets or aerosols containing respiratory secretions from coughing, barking and sneezing dogs. Dogs in close contact with infected dogs in places such as kennels, groomers, day care facilities and shelters are at high risk of infection. Canine Influenza can also be spread indirectly through objects (e.g., kennels, food and water bowls, collars and leashes) or people that have been in contact with infected dogs. It is important to clean and disinfect objects that have been in contact with an infected dog to avoid exposing other dogs to the virus. People who have been in contact with an infected dog should wash their hands and their clothing to avoid spreading the virus.
The virus can remain viable (alive and able to infect) on inanimate surfaces for up to 48 hours, on clothing for 24 hours, and on hands for 12 hours. It essential to implement biosecurity protocols and disinfection procedures to reduce the risk of disease transmission.
H3N8 has an incubation period of 1 to 5 days, with clinical signs in most cases appearing 2 to 3 days after exposure. Dogs infected with H3N2 may start showing respiratory signs between 2 and 8 days after infection. Given this window, it is very possible that infected dogs could travel out of state unknowingly spreading the disease not yet exhibiting signs of illness. Dogs are actually most contagious during the incubation period and shed the virus even though they are not showing clinical signs of illness. Some dogs may show no signs of illness and have a subclinical infection, yet still shed the virus.
Virtually all dogs exposed to Canine Influenza virus become infected, with approximately 80% developing clinical signs of disease. The approximately 20% of infected dogs that do not exhibit clinical signs of disease can still shed the virus and spread infection. Like other mammalian influenza viruses, Canine Influenza virus causes acute respiratory infection in dogs. There is no canine influenza “season”, and outbreaks can occur at any time of the year. Canine Influenza virus infection often at first is similar to kennel cough, which is caused by one or more bacterial or viral infections, including Bordetella bronchiseptica, adenovirus type 2, and parainfluenza virus.
The main difference between kennel cough and Canine Influenza is that Canine Influenza cough is more severe and lasts longer, there is commonly mucus coming from the nose with a lot of sneezing, and pneumonia often results from infection. The mortality rate of kennel cough is much lower than Canine Influenza, with Canine Influenza having a mortality rate of just under 10% of cases.
Treatment is with broad spectrum antibiotics to treat secondary bacterial infection, non-steroidal anti-inflammatory drugs to treat fever, and fluids to keep the patient hydrated. Prevention really is the best strategy to combat disease with the highly effective 2 strains vaccine manufactured by Zoetis and Merck. I would advise not waiting for you area to experience an outbreak before having your dogs immunized. The vaccine experienced prolonged back orders earlier this year due to supply chain issue, so it remains in limited supply. Case in point clinics in Minnesota are sold out of the vaccine the within a day of receiving the inventory.