Veterinary Advisory

Confirmed Cluster of Canine Influenza in Southern Ontario

A cluster of dogs infected with influenza A virus of the H3N2 subtype, commonly known as H3N2 canine influenza virus (H3N2 CIV), has recently been identified in the Simcoe-Muskoka area. From January to March 2018, 4 clusters of H3N2 CIV were identified in Essex County (2), Simcoe-Muskoka area (1) and Northumberland County (1), all of which appeared to have been successfully controlled. Canine influenza virus was not reported in dogs in Canada prior to 2018.

Investigation of the current cluster is ongoing. Cases are being managed using voluntary confinement of affected and in-contact dogs. Spread has been associated with affected dogs attending day kennels and other group activities. Infection control precautions in veterinary clinics are critical to prevent transmission in the hospital setting, including direct transmission between dogs (inpatients and outpatients) and indirect transmission by staff or animal owners when hands or clothing become contaminated with the virus. Prompt recognition and triage of potential CIV cases is essential, as is control of environmental contamination using commonly available disinfectants as part of an appropriate cleaning and disinfection protocol. An information sheet with basic guidelines for veterinarians is available (see Resources).

Canine influenza virus is of concern because it is highly transmissible between dogs, particularly in areas such as Canada where dogs do not have immunity from previous infection or vaccination. H3N2 CIV is widespread in some parts of Asia and continues to cause outbreaks in the United States, especially in animal shelters. Canine rescue organizations and other individuals are known to import dogs from affected areas into many regions of Ontario on a regular basis; therefore, all Ontario veterinarians and dog owners need to be vigilant. Testing of high-risk dogs that are showing compatible signs is recommended.

Canine influenza virus causes disease that is indistinguishable from other causes of canine infectious respiratory disease complex, commonly referred to as "kennel cough". Most dogs recover within 2 to 3 weeks with no treatment or with basic supportive care such as anti-inflammatories and cough suppressants. Canine influenza virus is more likely to cause severe disease or death in very young and old dogs, as well as brachycephalic breeds and dogs with underlying respiratory or cardiac disease.

Infected dogs can start shedding the virus shortly before onset of clinical signs (within 24 hours). Dogs that have contact with other dogs at events or facilities such as kennels, off-leash parks, classes or competitions are more likely to be exposed. It is recommended that dogs with suspected or confirmed canine influenza be kept away from other dogs for four weeks. H3N2 CIV can infect cats, but the likelihood of this appears to be low. Ferrets are susceptible to a range of influenza A viruses including H3N2 CIV.

Vaccines against infection with influenza A viruses affecting dogs (H3N2 and H3N8) are available in Canada and can help reduce the likelihood and severity of disease. Vaccination is recommended for dogs at high-risk of exposure in areas with confirmed cases of CIV. Given the ongoing risk of further introductions of CIV from imported dogs or those travelling from areas where the virus is actively circulating, vaccination should be a consideration for dogs at high-risk.

Canine H3N2 influenza virus emerged in Asia by transmission of an avian H3N2 virus from birds to dogs and is different from the human H3N2 influenza virus causing a seasonal flu in people. There is no known human risk from H3N2 CIV; however, there is a risk of reassortment between H3N2 CIV and human seasonal influenza viruses. Individuals with concerns about their own health after close contact with an infected dog should contact the local public health unit or their physician.

Detection of influenza A viruses in animals is an immediately notifiable hazard and is reported by animal health laboratories to OMAFRA under the Animal Health Act. As of January 1, 2018 novel influenza strains (those not known to already be circulating in Ontario) in any domestic animal, including H3N2 CIV, must also be reported to the local public health unit. Veterinarians are reminded that if specimens are submitted for testing to any laboratory outside of Ontario, the submitting veterinarian is solely responsible for relaying any notifiable or reportable results to the appropriate agency.


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