Respiratory Disease in Ruminants

Respiratory Disease in Cattle and Sheep

• Respiratory disease in cattle and sheep is a significant and costly issue.
• Autumn-born calves are more severely affected.
• 30% of pens show clinical signs, and up to 70% show lung damage at slaughter.
• Economically, the UK costs approximately £80 million annually.

Learning Objectives

• Creating a differential diagnosis list based on history and clinical presentations associated with airway disease, also including diagnostics.
• Determining appropriate medical and surgical interventions for airway diseases in ruminants.
• Determining the prognosis for individual animals and herds.
• Establishing prevention control measures for airway diseases in ruminants.

Lung Anatomy

• Ruminant lungs have a small area.
• Small tidal volume and surface area.
• High respiratory rate (RR).
• This makes them more susceptible to disease.

Differential Diagnoses

• Bovine Respiratory Disease (BRD): Respiratory disease in cattle.
• Diphtheria
• Aspiration pneumonia: A lung infection caused by inhaling foreign material.
• Lungworm
• Infectious Bovine Rhinotracheitis (IBR)
• Fog Fever
• Tuberculosis
• Malignant Catarrhal Fever
• Ovine Pulmonary Adenocarcinoma
• Maedi Visna
• Laryngeal Chondritis
• Nasal Bots

BRD Pathogens

• Viruses: Parainfluenza virus type 3 (PI3), Bovine Respiratory Syncytial Virus (BRSV), Bovine Herpes Virus type 1 (BHV1, causing IBR), Bovine Coronavirus, Bovine Adenovirus type 3.
• Bacteria: Mannheimia haemolytica,Pasteurella multocida, and Histophilus somni.
• Mycoplasma: Mycoplasma bovis and Mycoplasma dispar.

BRD Disease Complex

• Disease complex is a factor.
• Multiple primary pathogens are involved.
• Multifactorial interactions occur.
• Concurrent infections are possible.

Environmental Risk Factors

• Temperature
• Ventilation
• Ammonia
• Seasonal changes
• Stocking density
• Mixed-age groups
• Bedding

Host Risk Factors

• Failure of passive transfer.
• Stress (transportation)
• Nutrition
• Husbandry events

Acute BRD Presentations

• Primary URT viral infection.
• Secondary bacterial pneumonia (infection of the lungs after a viral infection).
• Shipping fever: primary bacterial infection, secondary to stress; Mannheimia haemolytica (and possible other pathogens).

Chronic BRD Presentations

• BRD pathogens, secondary to acute infection
• Truepella pyogenes (causes lung abscesses)
• Poor production/growth rates

Clinical Signs of BRD

• Pyrexia
• Nasal discharge: watery, mucopurulent
• Cough
• Ocular discharge
• Lethargy
• Inappetence
• Rapid shallow breathing, increased respiratory rate (RR)
• Increased heart rate
• Outstretched neck indicative of respiratory distress
• Inability to determine pathogen from clinical signs alone

Acute vs. Chronic

• Visual representation of different clinical presentations of BRD.

BRD Diagnosis

• Most common and costly disease of calves.
• Causes significant production losses.
• Winter outbreaks are common.
• Autumn-born calves are affected more severely.
• BRD is often under-diagnosed.
• 30% of pens show clinical signs; 70% have lung damage at slaughter.
• Clinical signs of BRD:* Pyrexia often precedes other problems, generalized URT respiratory signs, cough, nasal discharge, lethargy, rapid RR, and inappetence.

Diagnostic Testing

• Transtracheal lavage
• Broncho-alveolar lavage
• Nasal pharyngeal swabs
• Post-mortem samples
• Serology
• Ultrasound

BRD Treatment - Individual Animal

• Antibiotics: Likely secondary bacterial infection after viral insult (gram-negatives, facultative anaerobes). Lung tissue affected. Treatment duration is important; licensed products are available.
• NSAIDs: Licensed products available.
• Supportive care: Clenbuterol (under cascade approach), isolation, warmth, nursing, and nutrition.

Prevention and Management

• Reduce group size.
• Reduce shared airspaces to reduce pathogen mixing.
• Don't mix calves from different farms initially.
• Control concurrent infections.
• Manage environment: Temperature, Ventilation, Ammonia, Seasonal changes, Stocking Density, Mixed-age Groups, Bedding.
• Host risk factors include Passive transfer failure, Stress, Nutrition, and Husbandry events.
• Maintain optimal colostrum management.

Colostrum Management

• The 3Qs: Quantity, Quality, and Quickly.
• Quantity: 3 liters within 2 hours, similar feed within 12 hours.
• Quality: ≥ 22% immunoglobulin G (IgG) (50 mg/ml). Correctly store colostrum. Freeze colostrum for up to a year.
• Quickly: Within the first 24 hours. Check quality with refractometer to ascertain Brix %.

Control of Environmental Problems

• Inadequate inlet areas.
• Poor mechanical ventilation.
• Lack of high-level output.
• Humidity.

The Stack Effect

• Warm, humid air rises and exits through outlets at the top of the structure.
• Cooler, cleaner air is drawn in through inlets lower on the structure.