Canine influenza
Coming Soon to an Dog Near You!
Another winter in lovely New England is approaching and with it – the dreaded flu season. Unless you have been living under a rock, you have likely heard of the H1N1 virus, otherwise known as “swine flu.” Did you or your family decide to get vaccinated? Have you been home sick with the flu already? News anchors love talking about this stuff. Vaccine shortages, new outbreaks, or debates on vaccine safety are hot topics right now. So I’ve decided to jump on the flu bandwagon too. This month, I’m going to be writing about the flu, more specifically Canine Influenza. I’m not very familiar with this topic either, so we both get to learn something new this month!
Canine influenza (H3N8) is relatively new on the dog scene. The first recognized outbreaks occurred in racing greyhounds in Florida in early 2004. Since then, it has been spreading steadily. We luckily have not had any outbreaks in this area yet. Scientists believe the virus is related to an equine (horse) influenza virus that has adapted to cause illness and to spread between dogs. It is now considered to be a dog-specific H3N8 virus and it is highly contagious. Because this is a newly emerging disease, almost all dogs are susceptible, regardless of breed or age. Dogs, just like people, have little immunity to a disease to which they have never been exposed. Nearly 100% of exposed dogs will become infected, but only 80% may show clinical signs. This is important because any exposed dog should be considered an infectious risk, even without clinical signs, and therefore be quarantined from other dogs. The incubation period of this disease is 2-5 days after exposure. Infected dogs will start shedding the virus 2-4 days before any clinical signs, so dogs are infectious before you even know they are sick! But viral shedding only occurs for 7 days following exposure, which is a relatively short shedding period. This short life cycle is helpful for rescues and shelters trying to manage outbreaks.
Thankfully, the majority of dogs (~80%) only display mild clinical signs. These include low-grade fever, soft, moist or dry cough lasting 10-30 days, and purulent/mildly bloody nasal discharge. Some dogs may progress to developing a high fever (104-106) and pneumonia. A few dogs have died from this disease, but the overall death rate has stayed low (approximately 1-5%). So how do you tell if your dog has the flu? Well, this is can be a bit tricky. The clinical signs are non-specific and can be due to a number of diseases. A history of being boarded, traveling from endemic areas, or exposure to a shelter or rescue may make one suspicious of the flu. If your dog is well-vaccinated, other respiratory diseases such as canine distemper or kennel cough are less likely. And if only one dog is affected in a population, it is unlikely to be the flu. Remember, when the flu comes to an area, most dogs will develop signs. Therefore, one sick dog does not make you suspicious of the flu. Seeing thirty sick dogs with a cough and fever would be a little fishier. How the disease responds to treatment may also give you a clue. This is a viral infection. Viruses laugh in the face of antibiotics. Only bacteria are susceptible to antibiotics, so a poor response to antibiotics would more likely indicate a viral disease.
Testing to confirm the diagnosis can be done a few ways. Serology is most commonly used. This involves taking a blood sample during the acute infection and then again 2-3 weeks later. If there is a significant rise in the viral titer, the diagnosis can be confirmed. One obvious disadvantage is that this test cannot accurately determine active infection. It can only confirm a presumptive diagnosis. Two other tests, the Flu antigen ELISA and PCR, can be run on nasal swabs and are most sensitive during the first few days before and after the onset of signs. False negatives can occur after the onset of signs, so these tests are most useful in shelter or rescue situations to determine a dog’s exposure status. They are not always helpful in a hospital setting if a dog has been sick for more than several days.
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If you have ever had the flu, you should know the basic treatment plan is mainly supportive - maintaining hydration and controlling any fever. Antibiotics are often used to help treat secondary bacterial infections in mild cases. Cough suppressants should be avoided if the cough is productive. In more severe cases, dogs often need to be hospitalized and administered intravenous fluids and antibiotics. Cultures may be performed in cases of pneumonia to determine the best antibiotics to use. What about Tamiflu? I’m sure you have heard this drug mentioned in regards to treating H1N1 in humans. Unfortunately, it should not be used to treat influenza in our dogs for a number of reasons. First, Tamiflu (or oseltamivir) needs to be started within 48 hours of infection and we rarely recognize canine influenza that early. We don’t know the appropriate dose or duration of use in dogs either. But most importantly, this is a drug that represents the primary line of defense for human influenza pandemics and it should be held in reserve for the protection of human health.
Prevention and control are incredibly important in dealing with this disease. Again, unless you have been living under a rock, you have probably seen a step-up in the control of the H1N1 virus. Hand sanitizers are everywhere. Strangers shoot you a dirty look if you don’t cough into your elbow. News anchors are giving us lessons on how to wash our hands. Limiting the spread of any influenza virus is crucial. Shelters, rescues and boarding facilities are often ground zero of H3N8 outbreaks simply because of the numbers of dogs they see. But any dog show, agility competition, dog park or veterinary hospital are susceptible spots for an outbreak. Any dog in a facility at the time a case is identified should be considered exposed or at risk. These dogs need to be quarantined for two weeks from other naïve (or unexposed) dogs. This is a relatively short period of time compared to other infectious diseases that have longer incubation and shedding periods (such as canine distemper). Most shelters cannot afford to simply shut down for two weeks during an outbreak, but there are various ways of limiting the spread of the disease. Facilities can maintain separate wards and use strict isolation protocols to manage outbreaks.
A new vaccine for H3N8 has been developed by Intervet/Schering-Plough and is currently available. It was developed from an inactivated virus and it has been shown to reduce the incidence and severity of the disease. This vaccine can be given to dogs 6 weeks and older in a series of two subcutaneous injections, 2-4 weeks apart. Thereafter, it is given yearly as part of a dog’s routine preventative care. Now, don’t go rushing out and bug your veterinarian to vaccinate your dog for H3N8. Most veterinarians in this area do not carry this vaccine yet nor do many of us advocate vaccinating at this time. Remember, we have not seen this disease in this area. It may be some time before it rears its ugly head. However, if you are going to be travelling to an area that does have this disease, you should contact your veterinarian about possibly vaccinating your dog for H3N8. As canine influenza starts coming closer, we will likely start recommending every dog be vaccinated for it, especially those in an at-risk population (boarding, showing, traveling, etc). Talk with your veterinarian if you have any questions about vaccinating your dog.
Now, it is first and foremost up to you as dog owners to be responsible and protect your own dogs. These days, dogs are shipped from all over the country. Not everyone you adopt or buy a dog from may be reputable or will tell you about exposure status. It is important to monitor your dogs for any signs of contagious disease and keep them away from other dogs for at least two weeks. If you board your dog, send it to doggie daycare, or participate in any dog group activities, your dog is at risk for contracting this disease. I mentioned before that this disease has not made it up to our area yet, but it is only a matter of time. If you have the flu, you are supposed to stay home from work and not infect everyone else. The same goes for your dog, ok? Keep them home and away from other dogs – even if that means missing that fun doggie meet-up. You don’t want to be responsible for getting other dogs sick! And if your dog is showing any flu-like symptoms, please contact your veterinarian. Dogs can’t talk and tell us they feel lousy. It is up to us to catch any signs of illness early so they can be properly treated. Swine flu can knock you out for a week or more. Being stuck on the couch watching daytime TV is no fun for us and it’s no fun for our dogs. Be proactive about your dog’s health and protect them against the flu.
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