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Dog Flu, Canine Influenza

By California, Health and Human Services

October 2005 - Canine influenza, (dog flu) (canine flu) is a newly emerging virus that can cause a contagious respiratory infection in all dogs, regardless of breed or age. It was first isolated from ill racing greyhounds last year and has recently been associated with respiratory illness in some pet dogs in California.

What are the signs dog flu?

Many dogs exposed to the virus will not develop any clinical signs of illness. When dogs are ill with canine influenza, (dog flu), the signs are similar to a common disease known as “kennel cough.” The most common sign is a cough that persists for 10-21 days, longer than typical “kennel cough.” Affected dogs may also have a nasal discharge and a low-grade fever. A much smaller percentage of dogs develop a more severe disease with signs of pneumonia and a high fever. These dogs may require supportive care and hospitalization. If dogs receive medical attention early on, the fatality rate is very low.

Can I catch dog flu?

No, it is extremely unlikely that people can get canine influenza, (dog flu) from their pets. There are no known cases of canine influenza, (dog flu) infecting humans. Kennel attendants working closely with sick dogs have not reported any respiratory illness. Public health agencies are continuing to monitor this situation closely.

Is this similar to Avian Influenza (bird flu)?

No, this virus is very different from the one causing avian influenza that has killed birds and people in Asia.

What should I do if I think my dog has canine influenza, (dog flu)?

Contact your local veterinarian if your dog develops a persistent cough lasting more than several days or develops a thick, yellow nasal discharge. If your dog is coughing, keep it isolated from other dogs, and do not take it out to parks or areas where other dogs could get exposed.

How do I protect my dog?

Keep your dogs away from other dogs that are coughing or look ill. Wash your hands well after handling or petting any sick dog. The current “kennel cough” (Bordetella) vaccine does not protect against canine influenza, (dog flu). Veterinary researchers are currently developing a canine influenza, (dog flu) vaccine.

Veterinary Public Health Section/DCDC, MS 7308, P.O. Box 997413, Sacramento, CA 95899-7413 (916) 552-9740

Canine Influenza

By Mar Vista Animal Medical Center, Los Angeles, CA

In the last couple of 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 contain legitimate information while others contain half-truths or information that is simply wrong. We would like to take this time to sort out the facts from the theories from the misinformation.  Here is what we hope is a helpful FAQ:

What is Dog Flu?

Let's start with what an influenza virus is. Influenza viruses are a group of viruses. There are 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.

The virus has on its surface an assortment of proteins which 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 2003 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 the pet populations of many states outside of Florida, hence the recent barrage of email, news reports etc.

What Happens To Sick Dogs?

Infection rate is high but (depending on which report one reads) 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 actually get pneumonia. These dogs are those at risk for death and support becomes more aggressive: hospitalization, intravenous fluid therapy etc. Most of these dogs will recover as well, as long as they receive proper care.  Mortality rate is 5-8%

The incubation period is 2-5 days and the course of infection lasts 2-4 weeks. Because this is an emerging disease, few dogs will have immunity to it and there is currently no vaccine. This means that any dog is a candidate for infection.

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 cough do not be surprised if your veterinarian wants to look at chest radiographs and considers hospitalization.

How is Dog Flu 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 bring the virus home accidentally 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). Pneumonia in the dog is virtually always secondary in this way (meaning that an initial condition damages the lung allowing bacterial invaders to settle in) and treatment is similar regardless of the cause.

One treatment that might be different in this disease vs. other pneumonias or respiratory disease is oseltamivir (Tamiflu®).  This is an antiviral medication used in treating human influenza and is helpful only if used early in the course of infection or in prevention of infection in exposed dogs.

Can A Dog 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?

Several emails circulating indicated that veterinarians should submit sterile pharyngeal swabs (throat cultures) for testing, and this is not true and not useful. The most reliable test is a test for antibodies against the influenza virus (a blood test). Ideally, a second sample is submitted approximately 2 weeks later. The change in antibody titer is what clinches the diagnosis. Serum samples are sent to the Animal Health Diagnostic Center at Cornell University, and one should expect about a week for results to come in.  After October 1, 2005, this testing is no longer free of charge.  Your veterinarian's office will be able to determine costs.

There are two other tests which the laboratory at Cornell also runs. They are interested in throat cultures from dogs with high fevers and minimal other clinical signs. These dogs may be very early in the course of infection and at a time where the virus can be isolated. (Later in the course, when symptoms are more obvious, virus isolation is not possible and the culture is not useful after this brief initial window of opportunity.). Such testing is currently done at no charge (though there may be a shipping fee for the sample).

The other test is virus isolation from lung tissue of any dogs that have died of hemorrhagic pneumonia. This testing is also done at no charge (though there may be a shipping fee for the sample)

Does Vaccination Against Kennel Cough (BORDELTELLA) OR PARAINFLUENZA offer Any Protection Against Canine Influenza?

No. These are all completely different infections; however, work on the development of a canine influenza vaccine is underway.

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." One should not be concerned about getting an influenza infection from a dog, horse, or any other species other than a fellow human being.

Many emails and bulletins circulated have overblown the facts of this infection and created some panic among dog owners.

The way to look at the situation is similar to the way one would look at the flu for oneself.

Dogs can get their own flu. Some dogs get very sick and some do not.

Sick dogs need veterinary care to get through their infection.

Some dogs die from this infection just as some people die from the flu.


Center for Disease Control (CDC) Media Briefing on Canine Influenza:

UF College of Veterinary Medicine Veterinary Advisory on the Canine Influenza Virus : Canine flu factsheet

State of California, Health and Human Services Agency

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Updated: Dec 21 2013