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tvpjournal.com Today's Veterinary Practice July/August 2014 30 B ordetella bronchiseptica and canine influenza virus (CIV) are common causes of infectious tra- cheobronchitis and, occasionally, pneumonia. Combined, these and other pathogens cause the canine infectious respiratory disease complex (CIRDC), often referred to as kennel cough or infectious tracheobron- chitis. The multitude of bacterial and viral organisms associated with CIRDC are listed in Table 1. In general, morbidity for CIRDC is high with mortal- ity being low. Severe cases can result in life-threatening respiratory compromise due to pneumonia. DISEASE PROFILE Bordetella bronchiseptica B bronchiseptica, a primary respiratory pathogen, is a gram-negative, aerobic coccobacillus that is often impli- cated as a complicating factor in dogs with concurrent viral respiratory infections. 1 Virulence Factors. After B bronchiseptica colonizes the airways, it can evade the immune system by express- ing various virulence factors that lead to: 1,3 • Direct cellular injury of respiratory epithelium • Impaired immune recognition • Disrupted immune clearance. Perhaps one of the most unique and important effects of these virulence factors is the ability to paralyze the mucociliary apparatus—a key component of the respi- ratory tract's local defense mechanisms—and create acquired ciliary dysfunction. 1,3,4 The mucociliary apparatus moves inhaled debris and opportunistic pathogens away from the lower respiratory tract, decreasing the risk of colonization by these organ- isms and the potential for associated pneumonia. By paralyzing the cilia, B bronchiseptica not only improves its own virulence and chance for colonization, but also predisposes the patient to opportunistic infections of the lower respiratory tract. 1 Disease Spectrum. The spectrum of disease that results from infection with B bronchiseptica is wide, with some dogs manifesting mild disease characterized by nasal discharge and intermittent cough and others devel- oping severe pneumonia that can be life threatening. Canine Influenza Virus CIV (H3N8) is most closely related to equine influenza virus, which suggests that a direct transmission from horses to dogs occurred. 5 CIV was first detected in rac- ing greyhounds in Florida, and since has become more prevalent among pet dogs, especially those in kennels, shelters, and multidog households. 6 Prevalence. The prevalence of serum antibodies against CIV in dogs with no clinical signs of respiratory disease has been shown to be 0.5% to 3%, depending on the risk of the population being evaluated (Figure 1). 6 Diagnostic & therapeutic approach Dogs Infected with Bordetella bronchiseptica & Canine Influenza Virus (H3N8) Peer reVIeweD Table 1. bacterial & Viral Pathogens associated with CIRDC 1,2 BACTERIA • Bordetella bronchiseptica • Mycoplasmas (Mycoplasma cynos) • Streptococcus equi (subspecies zooepidemicus) CANINE VIRUSES • adenovirus 2 • Herpesvirus • bocavirus • Influenza virus • Coronavirus • Parainfluenza virus (pantropic strain) • Pneumovirus • Distemper virus • Reovirus • Hepacivirus • Respiratory coronavirus Laura a. nafe, DVM, Ms, Diplomate acViM (small animal internal Medicine) university of Wisconsin–Madison