Today's Veterinary Practice

JUL-AUG 2014

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July/August 2014 today's Veterinary Practice 73 Vital Vaccination: Kennel cough ReVisited | detella virulence is linked to a gene complex (Bvg) capable of expressing multiple, well defined virulence factors (toxins) that cause serious, rapid injury to respiratory epithelium. 9 Streptococcus equi subspecies zooepidemicus. Re- cently, S equi subspecies zooepidemicus, a gram positive bacterium, has gained attention as a zoonotic infection of horses. Although not a commensal organism in dogs/cats, S zooepidemicus is capable of colonizing upper respiratory epithelial cells of dogs and cats. It appears to be a signifi- cant cofactor in upper respiratory infections of dogs and cats and has been attributed to fatal necrohemorrhagic pneumonia in outbreaks of CIRD in shelters. 3 Viruses Primary pathogens in CIRD include: 5,7 • Canine parainfluenza virus (CPiV) • Canine adenovirus-2 (CAV-2) • Canine influenza virus (CIV) • Canine distemper virus (CDV). Additional viruses recovered from dogs with CIRD include: • Canine respiratory coronavirus (CRCoV): Shelter/ken- nel-housed dogs with CIRD in Europe, Japan, and the U.S. 6 • Canine pneumovirus (CnPnV): Recovered from respi- ratory tract of coughing dogs in the U.S. 4 These dogs were found to carry other known pathogens involved in CIRD; however, the significance of CnPnV in causing, or contributing to, CIRD is still unknown. SPECTRUM OF CLINICAL MANIFESTATIONS Clinical signs vary based on the individual agent respon- sible for infection in clinically affected dogs. Viral pathogens tend to be associated with clinical signs ranging from acute onset, highly contagious cough with expectoration of mucus that typically lasts 1 to 2 weeks to mild or no clinical signs (seroconversion only). Although coughing may persist for several weeks, dogs tend to ef- fectively clear infectious viruses within 2 weeks following onset of signs. Bacterial pathogens tend to be associated with not only cough, but systemic illness characterized by mu- coid to mucopurulent nasal and ocular discharge, fever, and loss of appetite. Other clinical findings include or- thopnea, dyspnea, and even life-threatening pneumo- nia, particularly in young animals. Clinical signs can persist for several days or longer depending on treat- ment administered. Clinical illness associated with individual pathogens, however, does not necessarily represent the spectrum of clinical manifestations encountered in practice. For exam- ple, reports of dogs with confirmed CIV infection indicate that some simply seroconvert without developing signifi- cant respiratory signs, while others die. However, it is unlikely that CIV, acting alone, causes such dramatic variation in clinical outcomes; CIRD likely results from the complex interaction between: • Host • Multiple respiratory pathogens acting together (viral and bacterial) • Environmental factors. The occurrence of co-infection explains, at least in part, why predicting clinical outcomes of CIRD in individual dogs can be difficult, and it explains why well vaccinated dogs still develop kennel cough. PREVENTION Vaccination Routine vaccination of dogs at risk for exposure is indicat- ed and generally effective in reducing severity of cough in challenged dogs, despite the inability to immunize dogs against each of the known CIRD pathogens. Table 1 lists the pathogenic viruses and bacteria associated with CIRD for which vaccines are available in the U.S. Several types of vaccine (Table 2, page 74) are available for administration to dogs by the intranasal, oral, and par- enteral (subcutaneous) route. The constituents and the routes of administration of commercially available vaccines vary. The route of vaccine administration indicated by the manufacturer must be strictly followed. Prophylactic Use of Antibiotics Although not indicated for the prevention of signs of CIRD in individual pets, I have utilized doxycycline, 5 mg/kg PO Q 24 H for 5 days, administered to all dogs entering a large animal shelter experiencing high rates (> 50%) of acute onset cough. Follow-up over a 30-day period indicated: • Rapid and substantial reduction in incidence of CIRD within the population • Higher placement rates • Reduced euthanasia rates • Lower operating costs. A necdotal obser vations suggest that empirical, daily administration of a broad-spectrum antibiotic may be of benefit in managing endemic respirator y disease associated with bacteria among shelter-housed dogs. W hile the cost of dox ycycline may prohibit implement- ing programmatic treatment of all dogs entering a shel- ter, other less expensive, broad-spectrum antibiotics are available and may augment attempts to reduce the frequency or severit y of CIR D in populations of co- housed dogs. Nosodes Nosodes are liquid homeopathic preparations, sometimes called homeopathic vaccines, containing minute amounts of infectious material (tissue/discharge) collected from actively infected, unvaccinated animals. Intended for oral administration, proponents of nosodes claim efficacy in, not only preventing, but also treating infectious diseases in dogs and cats. table 1. ciRd Pathogens for Which Vaccines are available in the u.s. • B bronchiseptica • cPiV • caV-2 • cdV • ciV

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