Performance of multiple diagnostic methods in assessing the progression of bovine respiratory disease in calves challenged with infectious bovine rhinotracheitis virus and Mannheimia haemolytica1

Abstract

The objective of this study was to evaluate the diagnostic performance of chute-side diagnostic methods for detecting physiological and pathological changes as indicators of early bovine respiratory disease (BRD) in calves experimentally inoculated with infectious bovine rhinotracheitis virus (IBR) and Mannheimia haemolytica (Mh). A challenge study was performed over 14 d in 30 Holstein steers [average weight (±SEM) = 211 kilograms (kg) ± 2.4 kg] inoculated on day 0 with IBR and on day 6 with Mh. Diagnostic methods included clinical illness scores (CIS), lung auscultation using a computer-aided stethoscope (CAS), rectal temperature, facial thermography, pulse oximetry, and bilateral thoracic ultrasonography. Animals were randomized into 1 of 5 necropsy days (days 6, 7, 9, 11, and 13) when the percentage of lung consolidation was estimated. The effect of study day on the results of the diagnostic methods and associations between each diagnostic method’s values with lung consolidation measured at necropsy were determined with mixed models. Values for all diagnostic methods differed significantly (P < 0.01) by day. During the IBR phase (days 0 to 6) calves had “normal” to “moderate” CIS, whereas during the Mh phase (days 6.5 to 13) scores were predominantly “severe” to “moribund.” Similarly, CAS scores were “normal” and “mild acute” during the IBR phase and “mild acute” to “moderate acute” after the Mh challenge. Oxygen saturation did not differ significantly between days 0, 1, 2, 4, and 6; however, significantly decreased 12 h after inoculation with Mh (P < 0.05). Mean lung consolidation between animal’s right and left side recorded by ultrasound was 0.13% (±0.07) before the inoculation with Mh. However, during the Mh phase, mean consolidation increased significantly over time (P < 0.05). The percentage of lung consolidation at necropsy ranged from 1.7% (±0.82) on day 6 to 55.4% (±7.49) on day 10. Clinical illness scores, rectal temperature, facial thermography, oxygen saturation, and ultrasonography were significantly associated (P < 0.05) with lung consolidation at necropsy. In addition, there was a significant trend (P = 0.07) between CAS and lung consolidation scores at necropsy. These chute-side diagnostic methods are useful for detecting disease progression on animals with early stages of BRD.

Evaluation of Antimicrobial or Non-antimicrobial Treatments in Commercial Feedlot Cattle With Mild Bovine Respiratory Disease Based on a Refined Case-Definition

“…Since a WS cannot be randomly assigned to an animal, inferences cannot be made between treatments across WS strata; conversely, those decisions can only be made within the chosen strata analyzed in the present study. Although prior studies have shown an association between a rising Whisper Score and worsening lung health ( 18 , 19 ) and calves enrolled with a WS ≥ 2 were lighter compared to calves with a WS = 1, the data generated in this study indicates that regardless of lung health status, calves in both WS strata require antimicrobial therapy to significantly reduce the risk of BRD relapse. This raises the question as to how to leverage the WS data.…”

Predicting Bovine Respiratory Disease Outcome Using Latent Class Analysis

“…Therefore, animals pulled with visual signs may have already resolved the viral infection by this time and consequently may not have returned a positive nasal swab result. It is also generally accepted that the overt visual signs of BRD are more often associated with secondary bacterial and in ammatory responses compared to the direct viral infection (22,23). Bacterial pathogens were not measured in the current study as the focus was on the initiating pathogens so this relationship could not be explored.…”

Predicting bovine respiratory disease outcome in feedlot cattle using latent class analysis

“…Therefore, animals pulled with visual signs may have already resolved the viral infection by this time and consequently may not have returned a positive nasal swab result. It is also generally accepted that the overt visual signs of BRD are more often associated with secondary bacterial and inflammatory responses compared with the direct viral infection ( Griffin et al, 2010 ; Baruch et al, 2019 ). Bacterial pathogens were not measured in the current study as the focus was on the initiating pathogens so this relationship could not be explored.…”