Equine Respiratory Disease: Understanding Causes, Signs, and Management

Introduction

Healthy respiratory function is essential for every horse, from pasture companions to elite athletes. Even mild respiratory disease can significantly impact comfort, performance, and long-term health. Equine respiratory diseases range from short-term infections to chronic inflammatory conditions, many of which are influenced by environment, management, and air quality.

Because early signs are often subtle, respiratory disease is frequently overlooked until performance declines or symptoms become persistent. Understanding how these conditions develop allows owners to intervene earlier and more effectively.

How the Equine Respiratory System Works

Horses are obligate nasal breathers with a highly sensitive lower airway system. Large volumes of air move through the lungs during exercise, making horses especially vulnerable to:

• Dust and particulate matter

• Mold and fungal spores

• Ammonia from urine

• Allergens and irritants

Repeated exposure leads to airway inflammation, mucus accumulation, and impaired oxygen exchange.

Common Equine Respiratory Diseases

Equine Asthma (Mild–Moderate to Severe)

What it is: Equine asthma is a chronic inflammatory disease of the lower airways, formerly referred to as inflammatory airway disease (IAD) and recurrent airway obstruction (RAO or heaves).

Typical Signs:

• Chronic or intermittent cough

• Nasal discharge

• Exercise intolerance

• Increased respiratory effort at rest (in severe cases)

• Improvement with turnout, worsening in the barn

Key Triggers:

• Dusty hay and bedding

• Poor ventilation

• Mold exposure

Infectious Respiratory Disease

Examples:

• Equine influenza

• Equine herpesvirus (EHV)

• Strangles

Typical Signs:

• Fever

• Lethargy

• Cough

• Nasal discharge

• Swollen lymph nodes (strangles)

These diseases are often acute and contagious, requiring isolation and veterinary care.

Exercise-Induced Pulmonary Hemorrhage (EIPH)

What it is: Bleeding within the lungs during intense exercise, most commonly seen in racehorses and high-performance athletes.

Typical Signs:

• Reduced performance

• Occasional nosebleeds (most cases are not visible)

• Diagnosed via endoscopy

Why Respiratory Disease Is Often Missed

Many horses continue eating and behaving normally despite compromised lung function. Early respiratory disease may appear as:

• Poor stamina

• Slow recovery after work

• Occasional cough that seems insignificant

These signs are often mistaken for poor fitness or aging rather than medical disease.

Diagnosis: Getting Accurate Answers

Veterinarians may recommend:

• Physical examination and rebreathing exam

• Endoscopy

• Tracheal wash or bronchoalveolar lavage (BAL)

• Imaging or lung function testing

Accurate diagnosis helps differentiate inflammatory disease from infection and guides targeted treatment.

Treatment and Daily Management

Environmental Management (Most Important)

• Improve barn ventilation

• Feed low-dust or soaked hay

• Choose low-dust bedding

• Maximize turnout when possible

• Reduce sweeping and blowing dust while horses are stalled

Medical Treatment

• Anti-inflammatory medications

• Bronchodilators when indicated

• Antibiotics only when bacterial infection is confirmed

Medication is most effective when paired with environmental changes.

Long-Term Management

Respiratory disease, particularly equine asthma, is typically manageable but not curable. Consistency is critical.

Successful management includes:

• Ongoing air quality control

• Monitoring for early flare-ups

• Adjusting exercise intensity during active disease

When to Call Your Veterinarian

• Persistent or worsening cough

• Nasal discharge lasting more than a few days

• Exercise intolerance

• Increased breathing effort

• Fever or lethargy

Early veterinary involvement can prevent chronic lung damage.