Agreement of nasal swabs, guarded nasopharyngeal swabs, and bronchoalveolar lavage relative to transtracheal wash for the diagnosis of viral and bacterial pathogens in dairy calves with bovine respiratory disease
Keywords:bovine respiratory disease, BRD, nasal swab, guarded nasopharyngeal swab, transtracheal wash, bronchoalveolar lavage, dairy cattle, calves
Bovine respiratory disease (BRD) is common in dairy calves, with 21.3% of mortality in preweaned calves and 50.4% of mortality in weaned heifers attributed to BRD (USDA NAHMS, 2002). Four sampling methods are used for antemortem identification of respiratory pathogens: the nasal swab (NS), guarded nasopharyngeal swab (NPS), transtracheal wash (TTW), and bronchoalveolar lavage (BAL). Each method has advantages and disadvantages. The TTW bypasses contamination from the nasopharynx, but the procedure is invasive and requires technical skill. The BAL and TTW directly sample the lower airways, but BAL, NS, and NPS can be contaminated by nasopharyngeal flora. Compared to NS, NPS provides a guarded sample of the pharyngeal recess, which maybe more representative of BRD pathogens. To our knowledge, no published study has compared the results of all four of these methods in cattle with clinical BRD. The objective of this study was to compare the agreement of results obtained by NS, NPS, or BAL with those obtained by TTW for isolation of BRD pathogens in dairy calves with acute undifferentiated BRD.