Respiratory Illness

Part of Veterinary Medicine

Recognizing, treating, and preventing respiratory disease in livestock — the leading cause of death in young animals globally.

Why This Matters

Respiratory disease is the number one killer of young livestock globally and a major cause of loss in adult animals under stress. Bovine Respiratory Disease (BRD) alone accounts for billions of dollars in losses annually in conventional agriculture — a figure that understates the true impact because it excludes subclinical disease that reduces growth rates without causing visible illness.

In a survival or rebuilding context, respiratory disease becomes even more dangerous because the conditions that drive it — crowding, stress, poor ventilation, nutritional compromises during transport or weaning — are precisely the conditions that a struggling community imposes on its animals. Animals that were scattered in the crisis are gathered, transported, housed together, weaned too early or under difficult conditions. Each stressor primes the respiratory system for disease.

Understanding respiratory disease in livestock means understanding that it is almost never a single pathogen acting alone. It is a complex interaction between stress, environmental challenge, primary viral infection, and secondary bacterial invasion. Addressing only the bacteria with antibiotics while ignoring the underlying drivers produces temporary improvement and recurring disease. Durable control requires addressing the whole picture.

The Respiratory Disease Complex

Respiratory diseases in livestock are classified as complexes because multiple pathogens typically interact:

Primary drivers: Viral infections weaken the respiratory mucosa, suppress local immunity, and create conditions for bacterial invasion. Key viral pathogens include:

• Cattle: IBR (Infectious Bovine Rhinotracheitis), BVD (Bovine Viral Diarrhea), PI3 (Parainfluenza-3), BRSV (Bovine Respiratory Syncytial Virus)
• Sheep/goats: Ovine respiratory syncytial virus, Mannheimia haemolytica bacterially-driven pneumonia
• Horses: Equine influenza, Equine herpesvirus (rhinopneumonitis)
• Pigs: Porcine reproductive and respiratory syndrome virus (PRRS), swine influenza

Secondary bacterial pathogens: Once primary viral infection has weakened defenses, bacteria proliferate in the lower respiratory tract. These cause the majority of the clinical illness and most of the fatal outcomes:

• Mannheimia haemolytica: The dominant bacterial pathogen in cattle and sheep respiratory disease
• Pasteurella multocida: Important in cattle, swine, rabbits, and poultry
• Mycoplasma species: Cause chronic pneumonia across multiple species; not responsive to penicillin
• Histophilus somni (formerly Haemophilus somnus): Cattle

Predisposing factors: Stress, crowding, poor ventilation (ammonia accumulation), weather stress (cold/wet or extreme heat), nutritional deficiency, weaning, transport, commingling of animals from different sources.

Recognizing Respiratory Disease

Early detection before severe lung consolidation dramatically improves outcomes. Watch for:

Stage 1 (early, excellent prognosis): Slightly elevated temperature (39.5–40°C), mild nasal discharge (clear, watery), slightly reduced appetite, mildly dull attitude. May still eat some feed. Lung sounds normal or mildly increased.

Stage 2 (moderate, good prognosis with treatment): Fever 40–41°C, cloudy to mucopurulent nasal discharge, significantly reduced appetite, obviously dull and depressed, increased respiratory rate, audible abnormal lung sounds (crackles on auscultation), possible cough.

Stage 3 (severe, guarded prognosis): Fever over 41°C or subnormal temperature (hypothermia in severe cases), very heavy purulent discharge, head extended and lowered (dyspnea), open-mouth breathing, obvious respiratory distress, lung sounds abnormal in multiple lobes, unable or barely able to rise, cyanosis possible.

The 5-minute rule: When you observe a suspicious animal, spend 5 minutes watching it breathe before approaching. Count respiratory rate, observe the breathing pattern, assess the effort required. A normal animal breathes without effort, with regular rhythm, at 12–30 breaths per minute (species-dependent). Labored breathing, abdominal push at expiration, nostril flaring, or elbows pushed out from the chest wall are all signs of respiratory compromise.

Treatment Approach

Environmental treatment first: Before medicating, address the environment. Move the sick animal to the driest, best-ventilated shelter available. Provide deep, clean bedding. Separate from other animals. Ensure clean water is accessible and within easy reach (sick animals will not walk far to drink). Reduce all sources of additional stress. These interventions alone will not cure bacterial pneumonia, but they are necessary for any treatment to be effective.

Supportive care: Fresh water, high-quality palatable feed (sick animals benefit from easy-to-eat options: softened grain, fresh cut grass, legume hay). Anti-inflammatory treatment if available: aspirin in feed (10–25 grams per 500 kg body weight, twice daily in cattle) reduces fever and inflammation, improving comfort and feed intake. This is not curative but supports recovery.

Antibiotic treatment: Where bacterial involvement is confirmed or strongly suspected (stage 2 or 3 disease, purulent discharge, fever over 40°C), antibiotics are the appropriate treatment. The challenge without laboratory diagnosis is identifying the most likely bacterial pathogen and selecting the appropriate drug class. Broad-spectrum antibiotics (oxytetracycline, tulathromycin, florfenicol in cattle) are typically the choices in clinical settings.

Traditional and botanical approaches: In the absence of pharmaceuticals:

• Eucalyptus steam inhalation: Boil eucalyptus leaves in water, hold the animal’s head over the steam (with a blanket to concentrate the vapor). Eucalyptol has documented mucolytic and mild antimicrobial properties. This provides symptomatic relief and may help mild infections.
• Garlic: Anti-Mannheimia and anti-Pasteurella activity has been documented. Fresh crushed garlic in feed or direct drenching. Not a substitute for antibiotics in severe disease.
• Thyme infusion: Thymol has documented antibacterial and antispasmodic activity. Can be administered as a strong tea drench.
• These approaches are most appropriate for stage 1 disease where the animal has a good chance of self-resolution with support.

Determining treatment duration: Treat for at least 3 full days after fever breaks and appetite returns. Stopping antibiotics at the first sign of improvement leads to relapse.

Pneumonia Assessment and Prognosis

Auscultate both sides of the chest daily during treatment. Normal lung sounds are present throughout the lung field. Pathological sounds:

• Crackles (rattling): Fluid in the airways — classic of pneumonia
• Wheezes: Narrowed airways — bronchospasm or mucus plugging
• Silence in a lung zone: Lung consolidation or pleural effusion — poor prognosis for that zone of lung tissue

Consolidated lung does not recover. An animal with significant bilateral lung consolidation will never be as productive as it was before — growth rates, milk production, and exercise tolerance are permanently reduced. Early treatment preserves lung function; late treatment may save the life but not the productivity.

Prevention

Ventilation: The single most impactful housing intervention. Adequate ventilation removes pathogen-laden air, reduces humidity, and eliminates ammonia that paralyzes respiratory cilia. Measure ventilation adequacy by smell — if you can smell ammonia when entering the housing area, ventilation is inadequate. Open ridge ventilations, natural cross-ventilation through sidewall openings, and avoiding over-insulation all improve air quality.

Avoid mixing and stress: Respiratory disease spikes when animals are mixed (combined from different sources), weaned, transported, or otherwise stressed. When these events cannot be avoided, minimize additional stressors and monitor intensively for 2–3 weeks after.

Vaccination: Where respiratory vaccines are available and the species is cattle, the core respiratory vaccines (IBR, PI3, BRSV, BVD) are highly effective at reducing severity. Administer before stressful events, not during or after.

Nutritional optimization: Vitamin A, selenium, and adequate protein intake all support respiratory mucosal immunity. Correct deficiencies before stressful periods.

Colostrum: Adequate colostrum intake in neonates provides maternal antibodies against respiratory pathogens for the first months of life. Calves, lambs, and kids that received adequate colostrum have dramatically lower respiratory disease rates than those that didn’t.