Canine Influenza

by Dr. Jean Hofve, DVM

Yes, dogs can get the flu, but fortunately not the H1N1 virus that’s been getting so much attention lately. Similar to the human form, canine flu is a contagious respiratory disease in dogs which is thought to be a mainly airborne virus, most likely transmitted by an infected dog coughing or sneezing on another. In otherwise healthy dogs, statistics show that the canine flu is a fairly mild disease with most dogs recovering completely in two to three weeks.

The canine influenza virus (CIV) was first noted in greyhounds about 5 years ago. CIV appeared quite dangerous at the time, with many deaths (now known to be due to secondary pneumonia arising from the conditions in which the greyhounds lived and worked). In the vast majority of dogs CIV produces only mild, self-limiting respiratory signs: coughing, sneezing, runny nose, and fever, for up to 3 weeks. It is similar to kennel cough in that antibiotics do not affect the course of the disease.

The canine flu is very contagious; and like human flu, it is most contagious during the 2-4 day incubation period before signs of illness appear, making prevention difficult. It is typically found in shelters, kennels, and other facilities where many dogs (especially puppies) are housed together.

A vaccine against CIV recently received conditional approval. However, again like human flu vaccines, it does neither prevents infection nor prevents symptoms. At best, it may reduce the severity and duration of illness, and it may reduce viral shedding by an infected dog. Because it is a killed vaccine, a 2-shot series is required, with 2-4 weeks between inoculations. Immunity develops slowly; so the vaccine doesn’t really take effect until 3-4 weeks after the first shot. Giving the vaccine after a dog has been exposed to the virus is therefore useless.

The CIV vaccine is considered non-core, and vaccination is not recommended for most dogs. Some boarding kennels are requiring vaccination for CIV; such requirements are not based on science, but on fear. CIV spreads through respiratory secretions and contaminated objects (kennel surfaces, food and water bowls, collars and leashes), and by people moving between infected and uninfected dogs without using proper precautions. The virus remains alive and infectious on surfaces for up to 48 hours, on clothing for 24 hours, and on hands for 12 hours. Good hygiene and isolation of infected dogs will limit, if not eliminate, transmission.

CIV, like many other viruses, is most likely to infect young puppies, and older dogs who already have other health problems. The best defense is a healthy immune system—that is, one that is well supported with great nutrition, appropriate exercise, and good stress management.

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