Canine H3N8 influenza virus infection in dogs and mice.
Authors: Castleman W L, Powe J R, Crawford P C, Gibbs E P J, Dubovi E J, Donis R O, Hanshaw D
Journal: Veterinary pathology
Summary
# Canine H3N8 Influenza Virus Infection in Dogs and Mice In 2004, an H3N8 influenza virus closely related to equine influenza emerged in racing greyhounds with respiratory disease and subsequently spread to shelter and pet dog populations, prompting detailed investigation of its pathological effects. Castleman and colleagues compared naturally occurring infections in dogs with experimentally inoculated beagles and mongrels (using the A/canine/Florida/43/2004 strain), whilst also establishing BALB/c mice as a potential experimental model by inoculating them with the same virus. All infected dogs developed necrotising and hyperplastic tracheitis and bronchitis with submucosal gland involvement, plus mild bronchiolitis and pneumonia, with viral antigen present in tracheal and bronchial epithelial cells in every case; importantly, spontaneously infected dogs frequently developed secondary bacterial pneumonia, and fatal cases showed severe pulmonary haemorrhage with haemothorax. Mice proved similarly susceptible to the virus, developing comparable airway inflammation with viral antigen identified in epithelial cells and type 2 alveolar cells, though infection remained localised to the respiratory tract in all animals tested. For equine professionals, this work demonstrates the zoonotic potential and respiratory pathogenicity of H3N8 in a closely related species, highlighting the importance of biosecurity protocols when working with dogs at equestrian facilities and emphasising that secondary bacterial infections can significantly complicate canine influenza cases clinically.
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Practical Takeaways
- •This study concerns canine influenza in dogs, not equine influenza in horses—the H3N8 virus identified is only 'closely related' to equine influenza virus and is not directly relevant to equine practice
- •The research is laboratory-focused on pathogenesis and experimental modeling rather than clinical management or prevention in working horses
Key Findings
- •H3N8 influenza virus identified in racing greyhound dogs with respiratory disease in 2004, subsequently found in shelter and pet dogs
- •All inoculated dogs developed necrotizing and hyperplastic tracheitis and bronchitis with viral antigen in bronchial and tracheal epithelial cells
- •Spontaneously infected greyhound dogs with fatal infection developed severe pulmonary hemorrhage with hemothorax and secondary bacterial pneumonia
- •BALB/c mice developed similar respiratory tract lesions and may serve as a suitable experimental model for canine influenza virus pathogenesis studies