Influenza viruses of an assortment of varieties have been the subject of concern for humans, wildlife, and domestic animals for many decades. Dogs were largely felt to be exempt from "the flu" until 2004 when a new canine influenza virus, clearly stemming from the equine influenza virus, was isolated from several groups of Florida racing greyhounds. The problem seemed confined to the racing industry until 2005 when cases involving pet dogs began appearing in boarding facilities.
In the last weeks of September 2005 and continuing into October, numerous warnings to dog owners about a new lethal canine disease swept the Internet. Some of these warnings contained legitimate information while others contained half-truths or information that was simply wrong. Let's sort out the facts from the theories from the misinformation.
Here is an FAQ regarding this relatively new virus that has come to be considered part of the kennel cough complex.
What is Canine Influenza?
|Group of influenza viruses
Let's start with what an influenza virus is. Influenza viruses represent a specific type of virus. There are actually three types (genera) of influenza viruses: type A (including the canine influenza virus), type B, and the less closely related type C. They produce fever, joint pain, and respiratory signs with which we are all familiar. Death is unusual but stems from respiratory complications and is most common in the very old and very young.
On its surface the virus has an assortment of proteins that determine its strain or subtype, and it is against these surface proteins that our bodies mount an immune response. If a viral strain mutates and sufficiently changes its surface proteins, a new strain is created. A new strain is one where the susceptible population has no immunity and infection can spread rapidly.
Unless a mutation occurs as described, influenza virus strains are specific to host species. Human influenza only infects humans. Equine influenza only infects horses. Canine influenza only infects dogs.
Molecular studies indicate that canine influenza represents a mutation from the equine influenza virus. Canine influenza was first confirmed in a racing greyhound in 2004 and has largely been a concern of the racing greyhound industry, particularly in Florida.
Starting in April 2005, the canine influenza virus has been seen in pet populations of many states besides Florida.
What Happens to the Sick Dogs?
Infection rate is high (depending on which report one reads) but 20-50% will simply make antibodies and clear the infection without any signs of illness at all.
The other 50-80% will get symptoms of the "flu:" they will have fevers, listlessness, coughing, and a snotty nose. Most dogs will recover with supportive treatment (antibiotics, perhaps nebulization/humidification, etc.). A small percentage of dogs will get pneumonia. These dogs are at risk for death, and support becomes more aggressive: hospitalization, intravenous fluid therapy, etc. Most of these dogs will recover as long as they receive proper care. Mortality rate is 5-8%
The incubation period is 2 to 5 days and the course of infection lasts 2 to 4 weeks. Because this is an emerging disease, few dogs will have immunity to it.
The point is not to ignore a coughing dog.
Do not allow your dog to socialize with coughing dogs. If your dog develops a cough, see your veterinarian.
If your dog develops a snotty nose, listlessness, and a cough don't be surprised if your veterinarian wants to look at chest radiographs and considers hospitalization.
How is the Disease Transmitted?
Dogs that are infected will shed virus in body secretions whether or not they appear to be sick. Virus transmission can occur from direct contact with an infected dog or with its secretions. Kennel workers have been known to accidentally bring the virus home to their own pets. The virus persists on toys, bowls, collars, leashes etc.
How are Sick Dogs Treated?
Fevers are treated with anti-pyretic medications or cool water baths. Pneumonia results from secondary bacterial infections (i.e. bacteria invading the lung after the virus has damaged the tissue and compromised its ability to defend itself). Pneumoniain dogs is virtually always secondary in this way, meaning that an initial condition damages the lung and allows bacterial invaders to settle in, and treatment is similar regardless of the cause.
One treatment that might be different in this disease versus other pneumonias or respiratory diseases is oseltamivir (Tamiflu). This is an antiviral medication used in treating human influenza and it is helpful only if used early in the course of infection or in prevention of infection in exposed dogs. For more details on this medication click here.
Can Dogs get Reinfected?
After a dog has recovered from canine influenza, immunity appears to last at least 2 years.
How are Dogs Tested for Canine Influenza?
In a perfect world there would be a simple test that could be performed on a single sample and yield unequivocal results, but there are two main ways to confirm canine influenza infection.
PCR testing is a method of testing involving amplifying small samples of DNA to make them more easily detectable. A nasal swab is used for the sample but timing is crucial; the sample must be obtained 3 to 4 days after the onset of symptoms. Because timing is difficult, this method is not commonly recommended.
Here, a blood sample is tested for antibodies against canine influenza virus and the antibody level is compared to that from a second sample taken later. The first sample is drawn within one week of the onset of symptoms and the second sample is drawn 2 to 3 weeks later. If the second sample shows a four-fold increase in antibody level, this indicates a true infection has occurred. This inconveniently means that diagnosis cannot be confirmed for several weeks after the dog has gotten sick. A single sample with antibodies only indicates that the dog has been exposed to influenza and does not clarify whether the infection is current, recent or in the long past.
Negative test results are not felt to rule out a diagnosis of canine influenza infection.
Does Vaccination against Kennel Cough (Bordetella) or Parainfluenza offer any Protection against Canine Influenza?
No. These are all completely different infections; however, a vaccine specifically for canine influenza has been released. While this type of vaccine does not completely prevent infection it does minimize the symptoms experienced from infection. Such a vaccine would be helpful for dogs that kennel frequently or for shelters where influenza has been a problem in the past.
Can People Get Infected?
People cannot get infected by this virus. Influenza viruses are specific for their host species and require a dramatic mutation in order to jump species.ï¿½ One should not be concerned about getting an influenza infection from a dog, horse, or any other species other than a fellow human being.
Questions we have received:
Q: A friend sent us a news story about the "dog flu," and now we're worried. It sounds really awful, and we want to know how to protect our pet. What do you advise? -- R.P., via e-mail
A: We checked with Dr. Melissa Kennedy, a clinical virologist at the University of Tennessee Veterinary Teaching College and infectious disease and immunology consultant for the Veterinary Information Network.
"Canine influenza virus (CIV) is a contagious viral disease spread most commonly among dogs with close contact or shared airspace, much like our influenza," she said. "Pet dogs at home are at very low risk. Dogs that board or frequently commingle with other dogs could be at risk."
What kind of risk are we talking about? "CIV is generally a mild disease, with typical symptoms of cough, some lethargy, fever and perhaps nasal discharge," said Kennedy. "As with the human influenza, there is a risk for secondary bacterial infections, which can be serious. This risk is highest among puppies and elderly dogs, where immunity may not be as good as in healthy adult animals."
Bottom line from Dr. Kennedy: "For most pet dogs, and probably most cases, it causes mild disease."
She confirmed that canine influenza is probably one of many causes of "kennel cough," although she used its more correct medical name, canine respiratory disease complex. "There are several viral and bacterial agents that may play a role in this disease complex, of which canine influenza virus is one," she said.
We asked her about the new vaccine, just approved in June. It's a killed virus vaccine and does not actually prevent infection with CIV. Nor does it protect your dog from becoming ill, although it might make his symptoms less severe (or not). And it also doesn't mean your dog, sick or not, can't infect other dogs, even after he's been vaccinated.
She said she does not consider the new canine influenza vaccine a "core" vaccine that should be given to every dog, but rather a tool that might be helpful in shelters, kennels or other environments where dogs are housed in close quarters and high numbers. She also agreed that vaccinated dogs, who can still be infected, could carry the disease home to other dogs.
Of course, influenza viruses are tricky things, and can mutate rapidly and unpredictably, so anything we say about CIV today could be wrong tomorrow. This virus could become nastier, or less nasty, over time; we really don't know. But for the moment, it's basically no bigger danger to our dogs than kennel cough is, which is to say, in most cases it will cause mild symptoms (or none). Yet in some dogs, particularly the very young, very old and immune-compromised, it can cause more severe illness and even death.
It can also be a real threat in crowded environments such as shelters or anywhere dogs are kept together in a confined space, and the new vaccine may have a role to play in those kinds of settings. But the average couch-sitting, yard-playing, park-walking pet probably isn't going to benefit from this vaccine, and probably isn't at much risk of severe illness from the virus, either -- anymore than we humans are from the common cold. -- Christie Keith
Schering Plough Animal Health's H3N8 Vaccination
Center for Disease Control (CDC) Media Briefing on Canine Influenza
UF College of Veterinary Medicine Veterinary Advisory on the Canine Influenza Virus
UC Davis School of Veterinary Medicine FAQ on Canine Influenza