Date Published: April 25, 2019
Publisher: Public Library of Science
Author(s): Grazieli Maboni, Mauricio Seguel, Ana Lorton, Roy Berghaus, Susan Sanchez, Simon Russell Clegg.
Canine infectious respiratory disease (CIRD) is a syndrome where multiple viral and bacterial pathogens are involved sequentially or synergistically to cause illness. There is limited information regarding the prevalence of pathogens related to CIRD in the United States as well as the role of co-infections in the pathogenesis of the syndrome. We aimed to conduct a comprehensive etiologic and epidemiologic study of multiple CIRD agents in a diverse dog population using molecular methods and statistical modeling analyses. In addition, a novel probe-based multiplex real-time PCR was developed to simultaneously detect and differentiate two species of Mycoplasma (M. canis and M. cynos). Canine adenovirus, canine distemper virus, canine parainfluenza virus, coronavirus, influenza A virus (H3N2 and H3N8), Bordetella bronchiseptica, M. canis, M. cynos and Streptococcus equi subsp. zooepidemicus were investigated in specimens from clinically ill and asymptomatic dogs received at the Athens Veterinary Diagnostic Laboratory. Results showed low occurrence of classical CIRD agents such as B. bronchiseptica, canine adenovirus and distemper virus, while highlighting the potential role of emerging bacteria such as M. canis and M. cynos. Statistical modeling analyses of CIRD pathogens emphasized the impact of co-infections on the severity of clinical presentation, and showed that host factors, such as animal age, are the most important predictors of disease severity. This study provides new insights into the current understanding of the prevalence and role of co-infections with selected viruses and bacteria in the etiology of CIRD, while underscoring the importance of molecular diagnosis and vaccination against this disease.
Canine infectious respiratory disease (CIRD), also known as “Kennel cough”, is an endemic syndrome with multiple viral and bacterial pathogens being involved in disease causation . CIRD is most common when dogs are kept in large groups with continuous intake of new animals, particularly in kennels, but also occurs in singly housed pets . Clusters of infection have also been documented in veterinary hospitals . Common clinical signs include nasal discharge, coughing, respiratory distress, fever, lethargy and lower respiratory tract infections [1, 3–5]. The clinical signs caused by the different pathogens associated with this syndrome are similar, which makes differential diagnosis challenging. Vaccination plays an important role in managing CIRD, and as such, several mono and multivalent vaccines are available ; however, despite the widespread use of vaccines to prevent CIRD, clinical disease is still common in vaccinated dogs [2, 6]. Vaccines are commercially available for some, but not all pathogens, which may explain the occasional lack of protection.
This study provided new insights into the etiology and epidemiology of CIRD associated pathogens using a molecular surveillance approach in a veterinary diagnostic laboratory. We explored two main aspects: (i) the rate of detection of nine CIRD associated pathogens by age, season, sex, clinical signs, and vaccination status; and (ii) the effect of co-infections on the severity of clinical disease. Our results indicated that the presence of co-infections and young age were associated with the severity of clinical signs. Additionally, we found a low occurrence of classical CIRD pathogens such as B. bronchiseptica, CAV and CDV, while identifying a higher than expected detection of bacterial agents such as M. canis and M. cynos.
This study provided new insights into the current understanding of the rate of detection of CIRD pathogens in the United States and the role of co-infections in disease severity, highlighting the importance of PCR panels for fast diagnostics. Key findings were that younger dogs and those with a higher number of co-infections are more likely to develop severe clinical signs, underscoring the importance of vaccination against CIRD at an early age. Our findings also highlight the low occurrence of classical CIRD agents such as B. bronchiseptica, CAV and CDV, while emphasizing the potential role of emerging bacteria such as M. canis and M. cynos. The developed real-time PCR assay for simultaneous detection of M. cynos and M. canis in clinical specimens provided results within 2h in a highly standardized format, representing a fast and efficient diagnosis alternative. The information presented here will help veterinarians obtain a timely etiologic diagnosis, and facilitate the selection of appropriate therapies and disease control measures.