Canine Influenza: What is it?
Canine influenza (CIV or dog flu) is caused by the canine influenza virus. It is highly contagious and easily spread from infected dogs to other dogs by 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.
Currently, two strains of CIV have been identified in the U.S.
Canine H3N8 influenza was first identified in Florida in 2004 in racing greyhounds. It is thought this strain developed from an equine H3N8 influenza strain that jumped from horses to dogs. Since being detected in 2004, canine H3N8 influenza has been identified in dogs in most U.S. states and the District of Columbia.
Canine H3N2 influenza was first identified in the United States in March 2015 following an outbreak of respiratory illness in dogs in the Chicago area. Prior to this, reports of canine H3N2 influenza virus were restricted to South Korea, China and Thailand. It was initially identified in dogs in Asia in 2006-2007 and likely arose through the direct transfer of an avian influenza virus – possibly from among viruses circulating in live bird markets – to dogs.
Following the initial diagnosis in Chicago, additional cases of canine H3N2 influenza were reported in a number of states. In early 2016, a group of shelter cats in Indiana were diagnosed with H3N2 canine influenza. It is believed the virus was transmitted to them from infected dogs.
In May 2017, canine H3N2 influenza was diagnosed in dogs in Florida, Georgia, North Carolina, South Carolina, Texas, Kentucky, Tennessee, Missouri, Louisiana, and Illinois. This was the same strain of H3N2 involved in the 2015 outbreak in Chicago.
There is no recent evidence that either strain of canine influenza (H3N8, H3N2) can infect humans. Canine influenza can occur year round.
Canine influenza symptoms and diagnosis:
The symptoms of a CIV infection resemble those of canine infectious tracheobronchitis ("kennel cough"). Dogs infected with CIV develop a persistent cough and may develop a thick nasal discharge and fever (often 104-105oF). The most common clinical sign is a cough that persists for 10 to 21 days despite treatment with antibiotics and cough suppressants. Other signs can include lethargy, eye discharge and reduced appetite. Canine influenza infections can cause mild to severe illness in dogs. Some infected dogs may not show any signs of illness, but can still be contagious and able to infect other dogs.
Some dogs are more severely affected and exhibit clinical signs of pneumonia, such as a high-grade fever (104°F to 106°F) and increased respiratory rate and effort. Thoracic radiography (chest x-rays) may reveal consolidation of lung lobes. Although most dogs recover without incident, deaths due to H3N2 have been reported (less than 10%). Anyone with concerns about their pet’s health, or whose pet is showing symptoms, should contact us. Laboratory tests are available to diagnose both H3N8 and H3N2 CIV.
Transmission and prevention of canine influenza:
Dogs infected with CIV are most contagious during the 2-4 day virus incubation period, when they shed the virus in their nasal secretions but do not show signs of illness. The virus is highly contagious and almost all dogs exposed to CIV will become infected. The majority (80%) of infected dogs develop flu-like illness.
To reduce the spread of CIV, isolate dogs (21-24 days) that are sick or showing signs of a respiratory illness and dogs known to have been exposed to an infected dog. Practice good hygiene and sanitation, including hand washing and thorough cleaning of shared items and kennels. Influenza viruses do not usually survive in the environment beyond 48 hours and are inactivated or killed by commonly used disinfectants, such as bleach (1:30 dilution) solutions.
Vaccines are available for both the H3N8 and H3N2 strains of canine influenza virus. 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 (Dog Shows, Daycare), grooming and visiting dog parks. We can provide you with additional information about the vaccines and whether you should consider vaccinating your dog. Please call our office with questions or concerns you may have.