Comparison of thoracic auscultation, clinical score, and ultrasonography as indicators of bovine respiratory disease in preweaned dairy calves

Abstract

Background: The diagnostic tools for bovine respiratory disease diagnosis include clinical inspection, thoracic auscultation, and ultrasonography.

Hypothesis: Thoracic auscultation and clinical examination have limitations in the detection of lung consolidation in dairy calves.

Animals: Prospective cohort of 106 preweaned calves from 13 different dairy herds (10 with a history of active bovine respiratory disease (BRD) in calves and 3 without suspected BRD problems).

Methods: Each preweaned calf was clinically inspected using the Wisconsin calf respiratory scoring chart (CRSC) and treatment history was noted. Systematic thoracic auscultation and ultrasonography then were performed, the latter focusing on lung consolidation. Mortality was recorded over a 30-day period.

Results: A total of 56 of 106 calves had ultrasonographic evidence of lung consolidation. The sensitivity of thoracic auscultation to detect consolidation was 5.9% (range, 0-16.7%). Only 41.1% (23/33) of calves with consolidated lungs had been treated previously by the producers. When adding CRSC and previous BRD treatment by the producer, sensitivity of detection increased to 71.4% (40/56). The area under the receiver operating characteristics curve was 0.809 (95% CI, 0.721-0.879) for the number of areas within the lungs with consolidation and 0.743 (95% CI, 0.648-0.823) for the maximal depth of consolidation as predictors of death within 1 month after examination. These were not significantly different (P = .06).

Conclusions and clinical importance: This study shows that thoracic auscultation is of limited value in diagnosing lung consolidation in calves. Ultrasonographic assessment of the thorax could be a useful tool to assess BRD detection efficiency on dairy farms.

Keywords: Atelectasis; Cattle; Parenchymal disease; Pneumonia; Radiology and diagnostic imaging; Respiratory tract.

Figure 1

Thoracic ultrasonographic and auscultation sites used in preweaned calves. Sites 1–8: Ultrasonographic sites at which thoracic examination was performed systematically. The median (Md) to ventral (Vt) parts of the thorax were divided into 4 auscultation areas (A–D). The auscultation findings were compared with ultrasonographic findings. The dorsal (Ds) third of the thorax was not examined.

Figure 2

Ultrasonographic evidence of consolidated lung in a preweaned dairy calf with bronchopneumonia. Consolidated lung in a Holstein calf (delimited by the white line), the DEPTH of consolidated lung parenchyma is indicated by the double arrowline (4 cm, each square is 1 cm²), 8.5 MHz linear probe, maximal depth 8.8 cm.

Figure 3

Maximal depth of consolidated lung determined by thoracic ultrasonography in relation to the clinical score of respiratory disease in 106 calves treated or not for bronchopneumonia. The maximal depth of consolidation (DEPTH) in centimeters has been plotted in relation to the Wisconsin Calf Respiratory Score Chart (clinical score) in previously treated (▼) and nontreated (○) calves. The plot has been divided into 4 different quadrants according to threshold of treatment based on the clinical score (if ≥5, this calf should be treated for respiratory problem, quadrants 2 and 4) and the significant consolidation (DEPTH ≥1 cm, quadrants 3 and 4) (arrows). Quadrant 1: Calves with a normal clinical score and absence of clinically relevant consolidation. Quadrant 2: Calves with a high clinical score and no clinically relevant consolidation. Quadrant 3: Calves with significant consolidation and no clinical suspicion of respiratory disease based on the clinical score. Quadrant 4: Calves with significant consolidation and clinical suspicion of respiratory diseases based on their clinical score.

Figure 4

Total number of thoracic sites at which consolidated lung was diagnosed by thoracic ultrasonography in relation with to the clinical score in 106 calves treated or not for bronchopneumonia. The number of sites at which consolidation was detected using ultrasonography (ΣsDEPTH) has been plotted in relation to the Wisconsin Calf Respiratory Score (clinical score) in previously treated (▼) and nontreated (○) calves. The vertical line separates the calves that should or should not be treated according to their clinical score.

Figure 5

Comparison of receiver operating characteristics curves for the number of consolidated sites and the maximal depth of consolidation (DEPTH) seen during thoracic ultrasonography as a predictor of death within 30 days. The ROC curve of the number of consolidated sites (ΣsDEPTH) is indicated with the continuous line and the maximal depth of consolidation (DEPTH) is indicated by the noncontinuous line. The line of identity is represented by the dotted line. Only 4 events of interest (deaths) occurred among the 106 calves.