What is Canine Influenza Virus?

Canine influenza is a highly contagious respiratory infection in dogs caused by a novel influenza A subtype H3N8 virus.

Where does CIV occur?

CIV has been documented in respiratory disease outbreaks involving thousands of dogs in shelter facilities, boarding facilities, pet stores, grooming facilities, and veterinary clinics in at least 25 states in the US.

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.

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, grooming facilities, dog shows, and racing kennels. Because CIV is a novel pathogen, dogs of any breed, age, or vaccination status are susceptible to the infection due to lack of pre-existing immunity.

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.

What are the clinical signs?

Canine influenza typically causes an explosive onset and spread of “kennel cough” in most dogs within a short period of time, usually less than two weeks. There is a sudden increase in prevalence of acute respiratory disease in the population, severity of illness, or a prolonged 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.

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

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 respiratory tract also occurs for 2-4 days after virus exposure. Since 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 ti 14 days after onset of clinical signs.

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 testing is based on the period of peak virus shedding.

For dogs with clinical signs for 1 to 3 days, nasal and pharyngeal swabs should be collected for detection of virus by PCR. IDDEXX has developed a canine respiratory pathogen PCR panel that detects the nucleic acid of 7 respiratory pathogens, including CIV, parainfluenza virus, adenovirus, distemper virus, herpes virus, respiratory coronavirus, and bordetella bronchiseptica,. Positive PCR results are most likely correct, but negative results may be “falsely negative” due to critical timing of swab collection with peak virus shedding.

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 conformation 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.

What is the treatment for CIV infection?

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

Is there a vaccine for CIV?

At this time, there is no vaccine to prevent CIV infection or reduce the clinical disease.

How is CIV infection managed?

Important management strategies for reducing spread of CIV infection within a premise include isolation of sick and exposed dogs, bio-security measures such as changing clothes and washing hands after handling affected dogs, and effective sanitation. All exposed dogs, with and without clinical signs should be quarantined for a minimum of 14 days. Influenza A viruses usually do not persist in the environment for more than 48 hours and are inactivated by detergents and disinfectants such as bleach.