Lucerne Veterinary Hospital Blog
Canine Influenza: An Update
Two years ago, a novel strain of the canine influenza virus alarmed the boarding facilities and animal shelters of Chicago by its rapid spread through the canine community. Veterinary hospitals saw increased numbers of dogs with high fevers, coughing, and sneezing. 1500 dogs became ill within 2 months, with 8 fatalities from pneumonia. Since the 2015 Chicago outbreak, there have been a few small outbreaks and a smattering of cases in several states. As of last month however, there is a new outbreak happening in eight states in the southeastern US, which seemingly stemmed from a dog show in Florida.
This newer influenza virus is an H3N2 strain, a mutation of an avian influenza virus originating in Asia. This is in contrast to H3N8, which is a mutated equine strain that has been present in the US since at least 2004. This new strain of influenza has proven to be more contagious than the old one, and also faster-spreading. In part this is because infected dogs remain contagious for 3 weeks (1 week longer than usual), even without necessarily showing any symptoms, and patients also produce as much as 100 times the number of viral particles.
At this time this new canine influenza virus poses no threat to humans, although it has been shown to be able to infect cats (though this is rare). Since dogs in the United States do not have any immunity to this virus, virtually all exposed become infected, with 80% showing signs such as coughing, sneezing, nasal discharge, high fever, decreased appetite, and lethargy. Most dogs are only mildly affected, but some can develop a life-threatening pneumonia. The overall mortality rate, however, is low at less than 1% so far in the US, with young, old, or debilitated patients at risk for greater morbidity and mortality.
A vaccine for the older flu strain (H3N8) was approved in 2009, and does not have any efficacy against the new influenza virus. Two companies have released a vaccine for the newer flu strain. There is no vaccine known to protect against both types of influenza virus.
In our area, it is still not currently recommended that all pets be vaccinated against canine influenza due to the limited risk of infection for most dogs. For dogs who are traveling around the country (especially to the southeast) and who may be exposed to many other dogs, vaccination may be warranted. This may include dogs who compete in national dog shows, or who are visiting locations affected by an outbreak. Both vaccines are given as a series of two boosters several weeks apart, and then boostered annually. While vaccination can greatly protect dogs, it does not grant complete immunity.
At this time, the influenza virus does not seem to be a great risk to dogs residing in Maine, but vaccination with both strains may be worthwhile for pets who are in contact with dogs from around the country. Consult with your veterinarian if you are unsure if the canine influenza vaccines would be warranted for your dog. Continue to monitor your pet for any respiratory signs and let your veterinarian know if you notice any.