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Infectious Diseases, Shawn K. Wayment, DVM

Canine Influenza Virus (H3N8) Update

What it is:  Canine Influenza Virus (CIV) is a very contagious virus in the Influenza A family that is closely related to the Equine Influenza A strain. It has been proposed that the equine virus adapted or evolved and emerged as a new canine-specific variety. The H and N nomenclature is important because these are the glycoproteins in the outer layer of the virus that the host (dog, human, horse, etc) cells produce antibodies against (natural infection with the virus &/or response to vaccinations).

The very first reported or recognized outbreak with the canine version of the H3N8 virus was in January 2004 in racing greyhounds from a Florida racetrack. Subsequently, the virus has been confirmed and documented in 30 states. CIV is very prevalent in the states of Florida, Colorado, New York and Pennsylvania.

Transmission: CIV is extremely contagious from dog to dog and can be transmitted through aerosolized secretions from the dog’s respiratory tract, contaminated objects (i.e. food and water bowls, tack and kennel surfaces, etc), and from our own hands and clothing. The CIV has been shown to be able to infect dogs from contaminated surfaces and human clothing for up to 24 hours. CIV is extremely contagious to dogs because it is a new emerging virus and there is very little natural immunity in our (naive) canine population from vaccinations or natural infections.

The incubation period is between 2 and 5 days from the time the dog is exposed to the CIV before they begin showing any clinical signs of influenza. It is very important to understand that dogs are the most contagious to other dogs during this incubation period before they’re even displaying any outward signs of disease. Infected dogs can shed or spread the virus for 7 to 10 days from the onset of clinical signs.
Because our canine population is naïve to CIV, virtually all dogs exposed to the virus will become infected; however, only about 80% will develop clinical signs. This means that roughly 20% will become infected and not display any outward evidence that they have CIV. Clinical signs include productive coughing, high fevers of 104 to 106 degrees F (normal dog temp. is 101 to 102.8 F), severe green nasal discharge, and clinical signs of pneumonia. The cough in some dogs is very similar to kennel cough caused by the bacterial infection from Bordetella bronchiseptica, but the cough tends to persist for 10 to 21 days even when the dog is being treated with antibiotics. It’s very important to note here that CIV is highly contagious but has a very low mortality rate 1 to 5% (and it appears to this author that mortality is over represented in racing greyhounds).

Diagnosis: CIV is most reliably diagnosed today by detecting antibodies to the H3N8 glycoproteins. These can be detected in an infected dog’s blood as early as 7 days after the onset of clinical signs. Veterinarians typically look at blood samples for antibodies at the onset of clinical disease and a second sample a few weeks later to watch for a rise in the antibody titer to the CIV virus. A single sample only confirms exposure to the virus or vaccination for that virus. Serological testing is currently being performed at Cornell University’s Veterinary Diagnostic Laboratory. Nasal or pharyngeal swabs and tissues samples can also be submitted to labs to aid in the diagnosis by PCR (detects viral RNA) testing and viral culture, which is less effective than the antibody serology.

Treatment: Is limited to supportive care as with most viral infections. Supportive care includes good nutrition, good housing conditions, antibiotics to prevent secondary bacterial infections, and maintaining good hydration (possibly via IV fluids).

Prevention: In kennels, boarding facilities and shelters the virus is easily killed with the commonly used disinfectants such as bleach and benzalkonium chloride solutions. Good hygienic protocols should be established by thoroughly cleaning all surfaces, bowls, and cages between usages. Remember that the virus can remain viable for 24 hours on clothing and surfaces. Wash hands, change your clothing, and disinfect all surfaces if there is any chance you have come in contact with an infected dog. Isolate sick or exposed dogs from others for a minimum of 14 days.

Vaccination: In May of 2009, the USDA approved a conditional license to Intervet/Schering Plough Animal Health Corporation for their H3N8 Canine Influenza Vaccine. The vaccine contains inactivated wholes portions of CIV subtype H3N8. The Canine Influenza Vaccine is consider a “life style” vaccine and is not recommended for every dog. Many states do not include it as one of their “Core” recommended vaccinations. The vaccine is intended as an aid in the control of the disease associated with CIV infections. Like many vaccinations, it may not prevent the CIV infection altogether but may significantly reduce the clinic signs of the disease, reduce shedding of the virus, and decrease the duration of the disease. Researchers also found that the incidence and severity of the lung disease was significantly reduced when dogs were vaccinated.
Dogs can be vaccinated (subcutaneously) as early as 6 weeks of age and need a booster in 2 to 4 weeks after the initial vaccine and then can be given annually as determined by you and your veterinarian. Due to the conditional licensing status with the USDA, the manufacturer of the H3N8 Influenza vaccine must continue to submit data obtained to support the products performance, safety, and efficacy.
We, as sporting dog owners, should always consult with our veterinarian to see if any vaccination is appropriate for our bird dog’s lifestyle. It’s very important to understand a few things about vaccines. First of all, there is no guarantee that being vaccinated with any vaccine will insure immunity towards that disease…H3N8 included. Furthermore, vaccinations for our bird dogs do not have to be FDA approved but rather USDA approved which does not have the stringent rules (FDA’s) applied to getting them to the pet industry. Manufacturers have to demonstrate that the vaccine they are marketing must be first and foremost safe for the animal and secondly they have to provide some evidence that the vaccine is effective towards that disease.



Running Dog


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