Canine Influenza

Just as you and I are susceptible to catching the seasonal flu, so are our beloved dogs. While both humans and dogs are susceptible to influenza, there are many different strains of influenza, none of which can pass from humans to dogs or vise versa. So, if you are suffering from the flu, don’t worry about getting your dog sick; it ain’t gunna happen.

There are three types of influenza; influenza A, influenza B, and influenza C. Like our seasonal flu and the H1N1 pandemic of 2010, the canine influenza virus is also a strain of influenza A, the subtype being H3N8.

There are also strains of influenza that effects birds, seals, and horses; this is how we ended up with canine influenza.

In January of 2004, the first cases of canine influenza was reported at a Florida dog racing track. The equine flu carried by race horses was transmitted to the dogs at the race track. This is what is known as antigenic shift or, the process that allows viruses to jump from one species to another species.

From American Veterinary Medical Association: “CIV represents a very rare event in adaptive evolution; the entire genome of the H3N8 equine influenza virus was transferred to dogs, and the virus adapted to the canine species to emerge as a new canine-specific virus. Although the virus spreads readily from dog to dog, there is no evidence to support that it can be transmitted from dogs to humans.”

The time between exposure to the influenza pathogen and when a dog starts to exhibit symptoms (called the incubation period) is roughly two to four days. Unfortunately, during this time when the infected dog is showing no symptoms is also the time when there is more viral shedding, meaning the dog is most contagious at this time.

A dog can be exposed to the virus by means of respiratory secretions from an infected dog (such as sneezing or simple respiration). Transmission of the virus can also take place by means of infected items like toys, water and food bowls, collars, leashes, clothing, and other items in which a dog may come into contact.

Viruses are masters of survival. A common virus that causes most all gastroenteritis (stomach flu), norovirus, can actually survive on hands cleaned with alcohol based hand sanitizer. The canine influenza virus can survive on human hands for approximately 12 hours. The virus can survive on clothing for 24 hours and on surfaces for 48 hours.

So far, its hard to determine the prevalence of the virus since the symptoms seems to mimic those of kennel cough (infectious tracheobronchitis). A dog infected with CIV may show symptoms of lethargy; low fever; runny nose; soft, moist cough. A minority of infected dogs exhibit a dry hacking cough which would be more closely resemble kennel cough.

Since the symptoms for CIV and kennel cough are so similar, a diagnosis cannot be made by clinical signs alone. Only a blood test can accurately determine whether or not a dog is infected with CIV.

If you happen to fall ill and discover that your illness is viral (as opposed to bacterial), there really isn’t any treatment other than supportive treatment. A physician might prescribe Tamiflu but, more than likely, he/she will tell you to get a lot of rest and drink plenty of water. Similarly, dogs will be required to get rest and fluids to aide in their recovery.

Infected dogs should be closely monitored as there is a chance that dogs can acquire a secondary bacterial infection which could include pneumonia.

The canine influenza virus is one that is very virulent, meaning it is highly contagious. In fact, nearly every dog that comes into contact with the virus will become infected, while nearly 20% of infected dogs will not demonstrate symptoms.

The terms morbidity and mortality are used in pathology (the study and diagnosis of disease) and epidemiology and can case a bit of confusion. So let me break it down: Morbidity rate describes the percent of subjects who, when exposed to the pathogen, will contract the pathogen. Mortality rate demonstrates the percent of infected subjects that will die due to illness.

The canine influenza virus has a morbidity rate of 80% (this is very high due to CIV being a new virus and dogs not having immunity), and the mortality rate 1-5% (low for influenza).

It should be noted that mortality is higher amongst dogs with secondary infections such as pneumonia.

As we discussed, the CIV is quite virulent but, it’s not exactly widespread. This virus remains active in pockets of the United States where dogs are confined to tight spaces such as shelters, dog parks, kennels, boarding facilities, veterinarian clinics, etc. As of September 2011, the virus has been found in 38 states which include: WA, OR, CA, ID, WY, NV, UT, AZ, CO, NM, KS, OK, TX, AR, IA, WI, IL, FL, GA, AL, SC, NC, TN, KY, WV, VA, OH, PA, DE, MD, NJ, NY, CT, RI, MA, NH, VT, and ME.

Currently there exists an effective vaccine for CIV. The vaccine has shown to significantly reduce the severity and duration of the influenza virus so, dogs that have become vaccinated and still become infected with the virus will have considerably reduced symptoms.

The American Veterinary Medical Association describes the CIV vaccine on their website:

“The canine influenza vaccine is a “lifestyle” vaccine, and is not recommended for every dog. In general, the vaccine is intended for the protection of dogs at risk for exposure to the CI virus, which include those that either participate in activities with many other dogs or are housed in communal facilities, particularly where the virus is prevalent. Dogs that may benefit from canine influenza vaccination include those that receive the kennel cough (Bordetella/parainfluenza) vaccine, because the risk groups are similar. Dog owners should consult with their veterinarian to determine whether their dog’s lifestyle includes risks for exposure to the CI virus, and if the vaccine is appropriate for their dog.”

I have spotted several blogs that seem distrustful of the CIV vaccine and will tell you not to vaccinate your dog due to supposed “lack of safety”. At the bottom of this article I link to a few extensive studies regarding the excellent safety and effectiveness of the CIV vaccine. As I quoted from the AVMA, consult your veterinarian when making a choice to vaccinate your dog as not all dogs require that vaccine (dogs that don’t socialize or do not have a risk for exposure).

References and Resources:

http://www.avma.org/public_health/influenza/canine_bgnd.asp

http://www.snopes.com/critters/crusader/dogflu.asp

http://www.doginfluenza.com/Owners/SpreadOfCIV.asp

PubMed articles showing strong efficacy for CIV vaccine:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3122572/

http://www.ncbi.nlm.nih.gov/pubmed/20037964

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2430215/

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