Associations between lung consolidation and serum amyloid A and haptoglobin, and the potential of acute phase proteins to differentiate primary respiratory tract pathogens in calves

• Published in: Journal of dairy science 2025-01, Vol.108 (1), p.943-953
• Main Authors: Lowie, Thomas, Jourquin, Stan, Stuyvaert, Sabrina, Hanley-Cook, Giles, Pardon, Bart
• Format: Article
• Language: English
• Subjects: Acute-Phase Proteins - analysis; Animals; antimicrobial therapy; Belgium; biomarkers; bovine respiratory disease; Cattle; Cattle Diseases - blood; Cross-Sectional Studies; Haptoglobins - analysis; pneumonia; quick thoracic ultrasonography; Serum Amyloid A Protein - analysis
• ISSN: 0022-0302; 1525-3198; 1525-3198
• DOI: 10.3168/jds.2024-25093

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Bovine respiratory disease (BRD) remains a leading cause of economic losses, hampered animal welfare, and antimicrobial use. The use of acute phase proteins (APP), such as serum amyloid A (SAA) and haptoglobin (Hp), has been explored for the detection of BRD, as defined by clinical signs. However, whether these APP are also associated with lung consolidation, as determined by thoracic ultrasonography, and have the potential to differentiate causative pathogens, is unknown. Therefore, the primary objective of this study was to explore the association between lung consolidation and SAA and Hp. The second objective was to determine the ability of both SAA and Hp to differentiate pathogen groups (Mycoplasmopsis bovis, viruses and Pasteurellaceae). Between 2020 and 2022, a cross-sectional study was conducted in Belgium, including 170 calves from 25 different herds with a history of Mycoplasmopsis bovis (endemic, n = 94, 9 herds) or herds (including M. bovis-positive herds) that met the inclusion criteria of an outbreak of BRD—that is, the presence of one or more clinical signs associated with BRD, affecting multiple animals (5 animals; 15% ill animals in the same airspace on a farm within a 48-h period; epidemic, n = 76, 16 herds). Clinical examination, quick thoracic ultrasonography, blood sampling, and non-endoscopic bronchoalveolar lavage were performed on each calf. Linear mixed effect models with a random intercept for herd were fitted, to determine the association between lung consolidations (depth ≥1 cm or ≥3 cm) or clinical BRD (UC Davis BRD scorecard positive) and serum SAA and Hp concentrations. Furthermore, multivariable models (linear mixed effect models) were used to evaluate the mutually adjusted associations between pathogen groups and APP concentrations. Test characteristics of APP concentrations to predict the presence of lung consolidation or pathogen groups were assessed, and potential SAA and Hp cutoffs, determined by Youden index, were evaluated. Lung consolidation (≥1 cm) was positively associated with higher Hp concentrations in epidemic conditions (regression coefficient [β]: 5.3; 95% CI: 1.4–20.3), and more severe lung consolidation (≥3 cm) was associated with higher Hp concentrations in endemic conditions (β: 3.6; 95% CI: 1.2–11.0). No positive association was found between lung consolidation a