Canine Influenza Virus: a fact sheet

1. What is canine influenza virus?

Canine influenza is a highly contagious respiratory infection of dogs caused by a novel influenza A subtype H3N8 virus. It is theorized that a similar influenza virus of horses mutated into a form that has been found to infect dogs. It is NOT the same influenza virus as the “Swine Flu” H1N1 that become a recent concern among young children and ill adults.

2. Where does CIV occur?

CIV has been documented in respiratory disease outbreaks involving thousands of dogs in shelter facilities, boarding facilities, pet stores, and veterinary clinics in at least 30 states in the U.S. Communities that are currently particularly affected with this virus are in Florida, Colorado, Pennsylvania, New Jersey, and New York.

3. What type of infection does CIV cause?

CIV causes an acute respiratory infection, and is part of the complex of viruses and bacteria associated with canine infectious respiratory disease (CIRD) or kennel cough. CIV infection alone can cause CIRD, but also occurs in co-infections with other canine respiratory pathogens such as parainfluenza virus, adenovirus, distemper virus, herpes virus, canine respiratory coronavirus, Bordetella bronchiseptica, Mycoplasma spp, and Streptococcus zooepidemicus.

4. Who is susceptible to CIV infection?

The risk for CIV infection is highest when large numbers of dogs are housed together in close confinement, such as boarding/training kennels, shelter facilities, dog shows, and racing greyhound kennels. Because CIV is a novel pathogen, dogs of any breed, age, or vaccination status are susceptible to infection due to lack of pre-existing immunity.

5. How is CIV transmitted?

As with other respiratory pathogens, CIV is highly contagious and is spread by direct dog-to-dog contact, aerosols of respiratory secretions, and contact with contaminated environments or people. The most efficient transmission occurs by direct contact with infected dogs and by aerosols generated by coughing and sneezing. Virus can also contaminate kennel surfaces, food and water bowls, collars and leashes, and the hands and clothing of people who handle infected dogs.

6. What are the clinical signs?

Canine influenza typically causes an explosive onset and spread of “kennel cough” in most dogs in the shelter within a short period of time, usually less than 2 weeks. There may be a sudden increase in prevalence of acute respiratory disease in the population, severity of illness, or a prolonged to complete lack of response to therapies that are generally effective for other causes of infectious canine respiratory disease.

Most exposed dogs develop a transient fever, cough, sneezing, and nasal discharge. The cough can persist for several weeks, even with antibiotic therapy appropriate for Bordetella bronchiseptica. Secondary bacterial infections cause purulent nasal discharge and even pneumonia in a few cases. Most dogs have the mild form of the disease, while less than 20% will develope the more serious form than can possibly lead to death.

Approximately 20% of exposed dogs will have a subclinical infection with no clinical signs, yet they shed virus that can infect other dogs. Therefore, all exposed dogs in the facility should be considered an infectious risk, whether or not they are showing signs of respiratory infection.

7. What is the incubation time and how long are dogs contagious?

The incubation period is 2-4 days from exposure to onset of clinical signs. Peak viral shedding from the respiratory tract also occurs for 2-4 days after virus exposure. Since the peak shedding period overlaps with the incubation period, infected dogs may be most contagious prior to showing obvious clinical signs. Virus shedding occurs for up to 7 days in most dogs, and to 10 days in some dogs. Once virus replication and shedding ceases, the dog is no longer contagious. Therefore, it is unlikely that dogs pose a significant infectious risk 10 to 14 days after onset of clinical signs.

8. How is CIV infection diagnosed?

Virtually all the viral and bacterial respiratory pathogens in CIRD cause similar clinical signs of coughing, sneezing, and nasal discharge. Therefore, CIV cannot be diagnosed based on clinical signs. Selection of diagnostic tests is based on the period of peak virus shedding. Dogs that have had clinical signs for 1-3 days may have samples sent to a laboratory for DNA “PCR” testing which costs between $130-180. Positive tests are reliable, however, negative test results do not always mean the pet is not infected since many dogs do not have detectable virus any longer at the time they are first presented to the veterinarian with clincal signs of coughing.
After 7 days of clinical signs, virus shedding has significantly decreased and may not be detectable by PCR. Serology becomes a useful test at this point due to development of antibodies. Serology is the most reliable diagnostic test for confirmation of CIV infection and should be performed in conjunction with PCR-based tests. However, it is not useful for diagnosis of acute infection since antibodies are generally not detectable for the first 10 days. Serology on paired acute and convalescent samples should be performed to confirm canine influenza.

9. What is the treatment for CIV infection?

There is no specific anti-viral therapy for CIV infection. Treatment consists of supportive therapy based on clinical signs. Broad spectrum bactericidal antibiotics should be used for secondary bacterial infections indicated by productive cough, purulent nasal discharge, and pneumonia.

10. Is there a vaccine for CIV?

At this time, a new vaccine that aids in the control of disease by decreasing clinical signs and severity of the disease has become available. The vaccine has received conditional liscensing from the USDA that supports a reasonable expectation of efficacy. Safety was established in trials involving more than 700 dogs. The vaccine requires an initial 2 injection series followed up with once a year boosters.

Which dogs should be vaccinated for canine influenza?

Dogs with similar risk factors for “kennel cough” should be considered possible candidates for the CIV vaccine, such as dogs taken to pet stores, doggie daycare, boarding facilities, veterinary clinics.

11. How is CIV infection managed?

Important management strategies for reducing spread of CIV infection within a premise include isolation of sick and exposed dogs, biosecurity measures such as changing of clothes and hand washing after handling affected dogs, and effective sanitation. All exposed dogs with and without clinical signs should be quarantined for a minimum of 14 days. The quarantined population should be separated from other populations by a physical barrier and managed with strict biosecurity procedures, including the use of PPE (gown, gloves, booties). Personnel managing the quarantined population should not visit the housing area for unexposed dogs or common use areas. If this is not possible, then personnel should manage the unexposed population first. Influenza A viruses usually do not persist in the environment for more than 48 hours and are inactivated by detergents and disinfectants such as diluted bleach, quaternary ammonium compounds or potassium peroxymonosulfates. All potential fomites should also be cleaned and disinfected.

Addendum: As of January, 2010 several cases of ferretts and 2 cats in Iowa and Utah and a dog in New York that have contracted flu like illnesses and pneumonia, with 1 cat death in Oregon have been attributed to the H1N1 “Swine Flu” aka North American Novel influenza virus. This information indicates that influenza upper respiratory viruses have the capacity to become infective under certain circumstances in non traditional species. Prudence dictates that persons with flu like clinical symptoms take the same infection control practices around their pets as they should do with other family members.