Over 1,000 cases and five deaths have been attributed to the recent Canine Influenza outbreak in Chicago during 2015. Increasingly, I have been asked my thoughts and opinions on the subject and if dogs should be vaccinated for this virus.
Canine Influenza Virus (H3N8)*
Canine influenza virus can be spread by direct contact with aerosolized respiratory secretions from infected dogs, by contact with contaminated objects, and by people moving between infected and uninfected dogs.
The number of dogs infected with this disease that die is very small. Some dogs have asymptomatic infections (no symptoms at all), while a few have severe infections. Severe illness is characterized by the onset of pneumonia, so infected dogs have a fever whereas those with plain kennel cough are typically without a fever. Although this is a relatively new cause of disease in dogs and nearly all dogs are susceptible to infection, about 80 percent of dogs will have a mild form of disease. If the dog is one of those that harbors Streptococcus organisms in their upper respiratory tract or lungs (uncommon), then the combination with canine influenza virus can be serious, and 2-3 % of these dogs can die.
Testing to confirm canine influenza virus infection is available at veterinary diagnostic centers. The tests can be performed using respiratory secretions collected at the time of disease onset or using two blood samples; the first collected while the animal is sick and the second 2 to 3 weeks later.
Available since 2009; the vaccine requires 2 doses 3 weeks apart and annual boosters. The Canine Influenza vaccine is considered a “lifestyle” vaccine and should be assessed according to your dog’s individual risk factors. Does your dog play at a dog park with other animals? Is he boarded in a kennel? Does he attend doggy daycare? Does your geographic location have increasing outbreaks or incidences of a particular disease? All of these factors should come into play when deciding whether to vaccinate your pet against the lifestyle vaccines.
The Chicago Outbreak of 2015
Chicago has a very dense dog population that is largely walked and attends dog-friendly venues such as parks, daycares and stores. Chicagoans say they can take their dogs anywhere! Unfortunately, while the disease is being reported all over the city and the suburbs, it is unknown what neighborhoods are the most affected. This is critical in determining whether or not your dog should or should not receive the vaccine or if your dog has already been exposed but is asymptomatic. Dogs that are asymptomatic can still be carriers and infect other dogs that may have compromised immune systems.
I agree with my veterinary colleagues and the Cook County Department of Animal Control and Rabies Control that all dogs should be restricted from dog-friendly areas and activities for at least the next 2-3 weeks to see if the outbreak will hopefully subside. When walking your dog, please do not allow your dog to say “hello” to the neighbor’s dog as well.
In this instance, dog caregivers in the Chicago area are encouraged to have an in-depth discussion with their veterinarians about the canine flu vaccine based upon the exposure risk where they live. If it is a high exposure area or depending on your dog’s lifestyle, he probably has already been exposed and the vaccine could be less effective. If you live in a low exposure area and do not take your pet to dog-friendly areas, vaccinating your dog may not be needed, unless you have special concern about the risk of his contracting the virus and spreading it to his dog friends.
When we released this statement, the veterinary and immunology communities believed this strain of Canine Influenza was H3N8. Cornell University issued a press release on April 12, 2015 that states that the ongoing canine influenza in the Chicago area is due to the H3N2 subtype of canine influenza, not the H3N8 subtype that has been seen in the U.S. previously. This is the first identification of the H3N2 subtype outside of Asia. At this time, it is not known if the currently available H3N8 vaccines will provide any cross-immunity to dogs exposed to the H3N2 subtype.
I do stand by my statement that dogs should be restricted from dog-friendly areas and activities until we know more about this outbreak.
*Extracted and adapted from Centers of Disease Control, http://www.cdc.gov/flu/canine/, 4.9.2015