Canine Influenza Virus: Should You Be Worried?

Like all vaccines, evaluate the risks, benefits, and efficacy

Like all vaccines, evaluate the risks, benefits, and efficacy

The Canine Influenza vaccine is a relatively new vaccine (approved in 2009) for a disease that has been recognized since 2004. Canine flu appears in most dogs like regular kennel cough. Twenty percent of dogs can be infected with no clinical signs. Five percent mortality has been documented. Dogs do die of this and some can get pretty sick with bacterial pneumonia; this can occur in previously healthy young dogs. Pneumonia usually shows up 10-12 days after exposure.  Of course, most dogs affected are not typically the healthiest of the crowd. And in some situations, it can spread. I would think that by now, it’s endemic and immunity is more prevalent.

It appears that infection after casual contact with an infected dog is not a major concern, as the virus is not shed at high levels and is not readily transmitted. Three to four days of continuous contact (like that seen in boarding kennels, for example) is needed for an infected dog to transmit the virus to a susceptible dog. It also appears that co-infection with other respiratory disease agents may be needed for dogs to show signs of the flu. Dogs that play in dog parks or participate in outdoor activities are unlikely to contract the flu virus in these environments.

After exposure to the virus, dogs start shedding the virus in secretions within 24 hours. They stop shedding the virus by 7 days after exposure. Clinical signs usually start by day 2-5 after exposure. Coughing, when present, can last for 30 days.

In one study of 700 dogs, the vaccine was reaction-free, most likely meaning without immediate reactions like fevers and injection site pain. The vaccine has not been in widespread use as of yet to determine further side effects; and of course, like most vaccines, it is difficult to connect chronic problems with any one vaccine that has been given. This is a killed vaccine with an adjuvant (like the rabies vaccines).

Currently we are suggesting that clients consider this vaccine only if their dogs will be at high risk for Canine Influenza (H3N8). Outbreaks have been noted recently in Chicago, also less recently in Delaware, and are mostly from crowded boarding facilities and shelters. Accordingly, if your dog will be boarding, showing, doing obedience trials, or being placed in other situations of prolonged contact with many dogs at once, you might want to consider this vaccine – or simply work on beefing up the immune system like we humans do during flu season.  Two doses given three weeks apart are required for the vaccine, and immunity does not occur until two weeks after the second dose.

Similar to the human flu vaccine, this vaccine, while effective at inducing immunity, does NOT prevent infection. In other words, dogs can still contract the virus and spread it to other dogs, although the amount of virus that is shed is reduced. Like the human flu vaccines, it may reduce the severity of an infection.

Based on the more recent findings that co-infection with Bordetella (commonly called ‘Kennel Cough’) and Parainfluenza (commonly included in many canine vaccines) may contribute to flu symptoms, vaccination with these (the simple intranasal vaccine) may help prevent clinical flu disease. Other viruses and bacteria can be responsible for these co-infections, but vaccines are not on the market for these agents.