Streptococcus zooepidemicus: an emerging canine pathogen.

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) has caused several outbreaks of haemorrhagic pneumonia in dogs in recent years. This highly contagious and often fatal disease is characterised by sudden onset of clinical signs including pyrexia, dyspnoea and haemorrhagic nasal discharge. Post mortem examination typically reveals pulmonary haemorrhage and pleural effusion. Histopathology demonstrates fibrino-suppurative, necrotising and haemorrhagic pneumonia in most cases. The pathogenesis of S. zooepidemicus infection in dogs is incompletely understood. Bacterial virulence factors as well as host factors may contribute to the severe outcome. S. zooepidemicus occasionally causes zoonotic infections with potentially serious consequences. Canine vaccines for S. zooepidemicus are currently not available and prevention of the disease therefore relies on limiting bacterial spread by implementing stringent control measures in kennels. Further research, particularly sequence analysis of canine strains, is required to gain insights into epidemiology and pathogenesis of this emerging disease.