Emergence and Containment of Canine Influenza Virus A(H3N2), Ontario, Canada, 2017–2018

Abstract

Canine influenza virus (CIV) A(H3N2) was identified in 104 dogs in Ontario, Canada, during December 28, 2017–October 30, 2018, in distinct epidemiologic clusters. High morbidity rates occurred within groups of dogs, and kennels and a veterinary clinic were identified as foci of infection. Death attributable to CIV infection occurred in 2 (2%) of 104 diagnosed cases. A combination of testing of suspected cases, contact tracing and testing, and 28-day isolation of infected dogs was used, and CIV transmission was contained in each outbreak. Dogs recently imported from Asia were implicated as the source of infection. CIV H3N2 spread rapidly within groups in this immunologically naive population; however, containment measures were apparently effective, demonstrating the potential value of prompt diagnosis and implementation of CIV control measures.

Phylogenetic Inference of H3N2 Canine Influenza A Outbreak in Ontario, Canada in 2018

“…In this study, we could show that clusters II and III shared a common ancestor of Chinese origin in the global phylogenetic tree (Fig. 4b) (7). Considering the time of infection, clusters II and III viruses were all sampled in March of 2018.…”

“…As clusters II and III were more closely related, this suggests that at least three introductions of CIV H3N2 occurred during the Canadian outbreak. While the origin and source of infection of epidemiological cluster I was correctly determined by a previous epidemiological investigation and molecular detection 7 , the origins of infection of clusters II, III, and IV remained unanswered. In this study, we could show that clusters II and III shared a common ancestor of Chinese origin in the global phylogenetic tree (Fig.…”

“…This virus has since caused an ongoing epidemic of disease through multiple, periodic introductions of Asian-origin H3N2 CIVs in the United States 5,6 . H3N2 CIV had not been identified in Canada until the end of 2017 7 . Multiple introductions with subsequent transmission of H3N2 CIV were identified in the Canadian province of Ontario between December 28, 2017, and October 30, 2018.…”

“…1). The origin of cluster C1 was associated with the importation of H3N2-infected dogs from South Korea 7 ; the origin of cluster C2 was unclear, and the origin of clusters 3 and 4 was presumably linked to dogs imported from China. Intensive contact tracing, testing of contacts and a 28-day isolation period for both infected and exposed dogs were implemented throughout the outbreak.…”

Canine and Feline Influenza

“…Some later outbreaks of H3N2 CIV in the United States and in Canada also appear to involve introductions of the virus from either Korea or China, and those spread for varying distances over the periods of the outbreaks (Fig. 3B) (Weese et al 2019). The epizoology of the H3N2 CIV involved introduction of viruses into an area (city or region) to cause a localized outbreak, which generally died out in a few weeks, likely once populations of dogs in kennels or animal shelters had been infected and had become immune.…”