Small Animal Review

Canine influenza virus (CIV) developed from other influenza A viruses as a result of adaptation, then spread within naive dog populations causing respiratory disease. Initially the H3N8 strain of equine origin appeared followed by a the H3N2 that originated in Asia from avian influenza virus. It was imported into the USA via infected dogs, where it was associated with respiratory disease and sporadic deaths.

A report from Weese et al describes the consequence of the virus's introduction into Canada (Emergence and Containment of Canine Influenza Virus A(H3N2), Ontario, Canada, 2017–2018. Emerg Inf Dis.2009;25:1810–1816. 10.3201/eid2510.190196). Influenza virus (CIV) A(H3N2) was found in 104 dogs in Ontario, between December 2017 and October 2018, in four primary epidemiological clusters.

Outbreak one involved two dogs imported from South Korea at the end of December, both of which presented with pyrexia, productive cough, and purulent nasal discharge on arrival, and from which CIV H3N2 was identified. They were sent to separate foster homes, following which all six canine contacts in those premises were infected within 1 week. Following a 28-day isolation period no further cases were identified. In outbreak two, a dog that belonged to a veterinary clinic employee developed upper respiratory illness. The owner had handled a dog that died with severe infectious respiratory tract disease a few days earlier. Two other canine contacts subsequently developed respiratory disease confirmed as CIV H3N2. The index case dog also had contact with a group of other dogs; of these, one was infected and developed mild respiratory disease. A 28-day confinement order was issued for the affected dogs.