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Title: Cilia-associated bacteria in fatal Bordetella bronchiseptica pneumonia of dogs and cats

item ABDELAZIZ, KHALED - University Of Guelph
item BASSEL, LAURA - University Of Guelph
item SCOTT, MELANIE - University Of Guelph
item CLARK, MARY ELLEN - University Of Guelph
item Register, Karen
item CASWELL, JEFF - University Of Guelph

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 8/17/2016
Publication URL:
Citation: Abdelaziz, K., Bassel, L., Scott, M., Clark, M., Register, K.B., Caswell, J. 2016. Cilia-associated bacteria in fatal Bordetella bronchiseptica pneumonia of dogs and cats. Journal of Veterinary Diagnostic Investigation. 28:369-376 doi: 10.117/1040638716646806.

Interpretive Summary: Bordetella bronchiseptica is an important cause of fatal pneumonia in dogs and cats. However, the bacterium is often under-diagnosed in these cases. The goal of this study was to determine whether microscopic detection of cilia-associated bacteria in histologic samples from the lung is a reliable predictor of infection with B. bronchiseptica. Thirty-six canine cases and 31 feline cases of pneumonia covering a 5-year period were studied retrospectively. Of 14 cases in which cilia-associated bacteria could be seen in lung samples, all were positively identified as B. bronchiseptica based on standard culture and biochemical testing, PCR and/or a positive reaction in tissue sections with an antibody specific for the bacterium. However, in only 2 of these 14 cases was the presence of cilia-associated bacteria noted in the pathology report. Thus, cilia-associated bacteria seem frequently overlooked by pathologists, but provide a specific and diagnostically significant feature of B. bronchiseptica pneumonia, particularly when other methods are not available or feasible. Identification of B. bronchiseptica is important because effective treatment that can prevent fatalities is available and because of the potential for spread of the bacterium to immunocompromised pet owners or to other pets in contact with the affected animal.

Technical Abstract: Bordetella bronchiseptica frequently causes nonfatal tracheobronchitis, but its role in fatal pneumonia is less well-studied. The objectives of this study were to identify the frequency of Bordetella bronchiseptica infection in fatal cases of bronchopneumonia in dogs and cats and to compare the diagnostic methods of culture, PCR, immunohistochemistry, and histologic identification of cilia-associated bacteria. Formalin-fixed case material and pathology records were retrieved from 5 years of archival material, including cases with diagnoses of bronchopneumonia or bacterial pneumonia, and excluding those that were neonates or had aspiration pneumonia, minor lung lesions, or alternative causes of respiratory signs. These criteria were met for 36 canine and 31 feline cases. Bordetella bronchiseptica was investigated by immunohistochemistry using a polyclonal antibody to pertactin, by PCR testing for the flagellin gene, and by bacterial culture data when available. Bordetella bronchiseptica was identified in 11/38 canine and 16/31 feline cases by either IHC, PCR or culture. Of these, IHC was positive in 6/11 canine and 7/16 feline cases, PCR was positive in 10/11 canine and 11/16 feline cases, and B. bronchiseptica was isolated in 2/4 canine and 3/8 feline cases tested. Histologic examination revealed bronchial cilia-associated bacteria in 5/31 feline and 9/38 canine cases, and all were positive by IHC, PCR or culture. In only 2 of these 14 cases were the presence of cilia-associated bacteria noted in the pathology report. Thus, Bordetella bronchiseptica was identified in 39% of fatal cases of bronchopneumonia, excluding those involving neonates or aspiration pneumonia. Cilia-associated bacteria seem frequently overlooked by pathologists, but is a specific albeit poorly sensitive feature. When only formalin-fixed tissues are available, PCR or IHC testing are useful for etiologic diagnosis. Identifying the specific cause is important because a vaccine is available and because of potential zoonotic risk to immunocompromised pet owners.