What is Canine Influenza? with Dr. Susan McMillan, owner
of Vet to Pet Mobile Veterinary Service in Burlington, Vermont.
As travel season ramps up, you need to know and understand
canine influenza and how to protect your pooch.
Susan, Welcome to Bark & Wag’s 15 minute Vet Talk – It is a
pleasure to have you on the podcast today. Please tell us a little
bit about yourself and your practice before we begin on the topic
of What is Canine Influenza?
Canine influenza (CI, or dog flu) in the U.S. is caused by the
canine influenza virus (CIV), an influenza A virus. It is
highly contagious and easily spread from infected dogs to other
dogs through direct contact, nasal secretions (through
barking, coughing or sneezing), contaminated objects
(kennel surfaces, food and water bowls, collars and leashes), and
by people moving between infected and uninfected dogs. Dogs of any
breed, age, sex or health status are at risk of infection when
exposed to the virus. In early 2016, a group
of cats in an Indiana shelter were infected with H3N2 canine
influenza (passed to them by infected dogs), and the findings
suggested that cat-to-cat transmission was possible.
Unlike seasonal flu in people, canine influenza can occur year
round. So far, there is no evidence that canine influenza infects
people. However, it does appear that at least some strains of the
Canine influenza symptoms and
CIV infection resembles canine infectious tracheobronchitis
("kennel cough"). The illness may be mild or severe, and infected
dogs develop a persistent cough and may develop a thick nasal
discharge and fever (often 104-105oF). Other signs can include
lethargy, eye discharge, and reduced appetite. Some dogs may
not show signs of illness, but can shed the virus and infect other
Most dogs recover within 2-3 weeks. However, secondary bacterial
infections can develop, and may cause more severe illness and
pneumonia. Anyone with concerns about their pet’s health, or whose
pet is showing signs of canine influenza, should contact their
CIV can be diagnosed early in the illness (less than
3 days) by testing a nasal or throat swab. The most accurate
test for CIV infection is a blood test that requires a sample taken
during the first week of illness, followed by a second sample 10-14
Cats infected with H3N2 canine influenza show symptoms of upper
respiratory illness, including a runny nose, congestion,
malaise, lip smacking, and excessive salivation.
Transmission and prevention of canine
Dogs are most contagious during the two- to four-day incubation
period for the virus, when they are infected and shedding the virus
in their nasal secretions but are not showing signs of illness.
Almost all dogs exposed to CIV will become infected, and the
majority (80%) of infected dogs develop flu-like illness. The
mortality (death) rate is low (less than 10%).
The spread of CIV can be reduced by isolating ill dogs as well
as those who are known to have been exposed to an infected dog and
those showing signs of respiratory illness. Good hygiene and
sanitation, including hand washing and thorough cleaning of shared
items and kennels, also reduce the spread of CIV. Influenza viruses
do not usually survive in the environment beyond 48 hours and are
inactivated or killed by commonly used disinfectants.
There are vaccines against the H3N8 strain of canine influenza,
which was first discovered in 2004 and until 2015 was the only
strain of canine influenza found in the United States. However, a
2015 outbreak of canine influenza in Chicago was traced to the H3N2
strain – the first reporting of this strain outside of
Asia – and it is not known whether the H3N8 vaccine provides any
protection against this strain. Used against H3N8, the vaccines may
not completely prevent infection, but appear to reduce the severity
and duration of the illness, as well as the length of time when an
infected dog may shed the virus in its respiratory secretions and
the amount of virus shed – making them less contagious to other
In November 2015, the U.S. Department of Agriculture granted a
conditional license to Zoetis to market the first commercially available H3N2 canine influenza
vaccine. Later that month, Merck Animal Health announced the
availability of an H3N2 canine influenza vaccine, also
conditionally licensed by USDA. None of the currently available
H3N2 canine influenza vaccines are approved for use in
The CIV vaccination is a "lifestyle" vaccination, recommended
for dogs at risk of exposure due to their increased exposure to
other dogs – such as boarding, attending social events with dogs
present, and visiting dog parks.
