Bovine Respiratory Disease (BRD), commonly referred to as calf pneumonia or "shipping fever," is the most common and costly disease affecting North American cattle.
Overview and Clinical Importance
Bovine Respiratory Disease (BRD), commonly referred to as calf pneumonia or "shipping fever," is the most common and costly disease affecting North American cattle. It is a multifactorial syndrome involving complex interactions between environmental stressors, host factors, and multiple infectious pathogens.
Aspiration pneumonia results from inhalation of foreign material into the lower respiratory tract. It requires special consideration due to its unique etiology and guarded prognosis.
High-YieldBRD is the leading cause of morbidity and mortality in beef cattle and second most common disease in dairy calves after neonatal diarrhea. Economic losses include treatment costs, reduced weight gain, decreased milk production, and mortality.
| Virus |
Abbreviation |
Key Features |
| Bovine Respiratory Syncytial Virus |
BRSV |
Most important primary viral pathogen; syncytial cells in bronchioles; subpleural emphysema |
| Infectious Bovine Rhinotracheitis |
IBR (BHV-1) |
Upper respiratory; latent infection; fibrinonecrotic rhinotracheitis with diphtheritic membranes |
| Parainfluenza-3 Virus |
PI3 |
Usually mild; predisposes to bacterial pneumonia; impairs mucociliary clearance |
| Bovine Viral Diarrhea Virus |
BVDV |
Immunosuppressive; PI calves are reservoirs; lymphoid depletion |
Etiology and Pathophysiology
Viral Pathogens
Viral infections initiate disease by damaging respiratory epithelium and suppressing immune defenses.
NAVLE TipRemember "BIG PP" for BRD viruses: BRSV, IBR, BVD, Parainfluenza-3, CoronavirusPneumonia. BRSV is the most important primary viral cause; BVDV is most immunosuppressive.
Bacterial Pathogens
High-YieldMannheimia haemolytica leukotoxin (LKT) kills bovine neutrophils and macrophages - SPECIES-SPECIFIC. Mycoplasma bovis lacks a cell wall, making it INTRINSICALLY RESISTANT to beta-lactam antibiotics.
| Bacterium |
Key Features |
Pathologic Findings |
| Mannheimia haemolytica |
Most common in feedlot; produces LEUKOTOXIN killing bovine leukocytes |
Fibrinous bronchopneumonia; "marbling" (fibrin in septa); coagulative necrosis |
| Pasteurella multocida |
Common in dairy calves; opportunistic; enzootic pneumonia |
Suppurative bronchopneumonia; cranioventral consolidation; less fibrin |
| Histophilus somni |
Causes septicemia; TME, myocarditis, arthritis |
Fibrinous pleuropneumonia; vasculitis; fibrinous polyserositis |
| Mycoplasma bovis |
Chronic pneumonia; 30-60 days post-arrival; RESISTANT to beta-lactams |
CASEONECROTIC bronchopneumonia; round white friable necrotic foci; polyarthritis |
Clinical Signs and Diagnosis
Exam Focus: Fever and depression precede respiratory signs by 24-48 hours. Thoracic ultrasound is 94% sensitive for detecting lung consolidation - much better than auscultation (only 5-10% sensitive).
| Stage |
Clinical Signs |
| Early |
Fever (40-41°C), mild depression, decreased feed intake, reduced rumen fill |
| Acute |
Mucopurulent nasal discharge, cough, increased respiratory rate (greater than 40/min), labored breathing |
| Severe |
Open-mouth breathing, extended head/neck, drooped ears, expiratory grunt, pleuritic pain |
| Chronic |
Poor body condition, rough hair coat, chronic cough, poor growth |
Aspiration Pneumonia
Causes
- Iatrogenic: Force-feeding, improper drenching, misplaced tube
- Anatomic: Cleft palate (ALWAYS examine in young calves with pneumonia)
- Metabolic: Milk fever with recumbency and regurgitation
- Neonatal: Meconium aspiration during dystocia
High-YieldAspiration pneumonia following milk fever treatment is often FATAL within 1-2 days due to endotoxemia. NEVER drench a recumbent cow!
Aspiration vs Infectious Pneumonia
NAVLE TipUNILATERAL + FOUL-SMELLING + NECROTIZING = Aspiration. Always ask about drenching, milk fever, or check for cleft palate!
| Feature |
Aspiration |
Infectious BRD |
| Distribution |
UNILATERAL; focal; may be caudal |
BILATERAL cranioventral; symmetrical |
| Odor |
FOUL, putrid, gangrenous |
Minimal unless chronic |
| Character |
NECROTIZING; brown-green; may have feed |
Firm consolidation; red-gray |
| Prognosis |
GUARDED to GRAVE |
Good with early treatment (80%) |
Treatment
High-YieldFor Mycoplasma bovis, use macrolides, tetracyclines, or florfenicol - M. bovis lacks a cell wall and is intrinsically RESISTANT to beta-lactams!
Aspiration Pneumonia Treatment
- Broad-spectrum with anaerobic coverage (florfenicol, penicillin + aminoglycoside)
- Consider metronidazole for enhanced anaerobic coverage
- NSAIDs for inflammation; supportive care
- Prolonged antibiotic course (7-14+ days)
NAVLE TipDo NOT attempt tracheal suction after aspiration - this disseminates aspirate further. Position head low, allow coughing.
| Drug |
Dose |
Notes |
| Tulathromycin |
2.5 mg/kg SC once |
Macrolide; excellent lung penetration; first-line for BRD |
| Florfenicol |
40 mg/kg SC once |
Broad spectrum; good for Pasteurella/Histophilus |
| Tilmicosin |
10 mg/kg SC once |
TOXIC TO HUMANS - no IV; cardiotoxic |
| Oxytetracycline |
20 mg/kg IM q24h |
Useful for Mycoplasma |
Prevention and Control
Key Strategies
- Colostrum: 4L within 4-6 hours; target IgG greater than 10 g/L
- Vaccination: Intranasal MLV at 1 week (bypasses maternal antibodies); injectable 3 weeks before stress
- Housing: Greater than 30 sq ft/calf; 4+ air changes/hour; ammonia less than 25 ppm
- Preconditioning: Vaccinate 2-3 weeks before weaning; minimize commingling
- Metaphylaxis: Mass treatment upon arrival for high-risk cattle
High-YieldIntranasal vaccines bypass maternal antibody interference and induce local IgA at mucosal surfaces. Can be given as early as 1 week of age.
Memory Aids
BRD Bacteria - "MoPHiT": Mannheimia (Leukotoxin), Pasteurella, Histophilus (TME), Trueperella
Aspiration Features - "FUNG": Foul odor, Unilateral, Necrotizing, Guarded prognosis