Difficulty Breathing (Dyspnea) in Horses

Key Takeaways

Dyspnea is difficulty breathing. In horses, it is characterized by an increased effort to breathe, usually evident in the character, rate, and rhythm of respiration. 

• Causes include chronic airway conditions (e.g. equine asthma), bacterial or viral infections, environmental triggers, and exercise induced trauma

• Nearly all cases of dyspnea are medical emergencies requiring urgent veterinary care

• Endoscopy, microscopic analysis of cells and fluid from the respiratory tract, and diagnostic imaging are used to determine the underlying condition

• Medications to clear mucus from the airways are often indicated regardless of diagnosis

• Vaccines are available for some of the pathogens that cause respiratory illness in horses

A Closer Look: What is Difficulty Breathing in Horses?

The most important variable with dyspnea is when it occurs. If the difficulty breathing occurs only during exercise, it could be a sign of inflammatory airway disease. If dyspnea occurs also at rest it might be an indicator of heaves.

Sudden acute dyspnea could be an indicator of a life-threatening condition and as such must be treated as an emergency.

Dyspnea that has developed recently is categorized as acute, while chronic dyspnea has persisted for longer than several days. Equine asthma is a very common cause of chronic dyspnea, while Exercise induced pulmonary hemorrhage (EIPH) and viral and bacterial infections are usually acute.

Possible Causes

The most common causes of respiratory malfunction in horses are:

• Equine asthma 

• Viral infections: including herpesvirus, influenza, equine arteritis virus

• Bacterial infections: including strangles or pneumonia

• EIPH

Another common cause is heaves, a reactive airway disease often caused by inhaling an allergenic antigen such as dust.

Risk Factors

Respiratory distress is always alarming and indicates a need for rapid veterinary intervention. It is less of a concern if it is temporary or intermittent, but still warrants a workup to pursue a diagnosis. Observations about when dyspnea occurs are helpful for narrowing down the diagnosis. If dyspnea occurs regardless of activity, the animal may suffer from equine asthma or other chronic conditions. When dyspnea is associated with exercise, the cause might be an inflammatory airway disease. 

Respiratory infections are very common in horses. The most common are equine herpesvirus and influenza.

Dyspnea can also be an indicator of a condition not directly related to the respiratory system. Difficulty breathing can occur in cases of heart conditions, exposure to toxins, or blood disorders such as anemia.

Testing and Diagnosis

Horses presenting with difficulty breathing will undergo the following diagnostics:

• Endoscopy of the upper airways • Diagnostic imaging of the skull, neck, and thorax

• Cytology of fluid/cells collected from flushing the upper respiratory tract

• Lung biopsy may be required in complicated cases

Treatment varies according to the underlying condition causing dyspnea. In most cases, respiratory difficulty involves the excessive production of secretions. The vet might prescribe medications (such as expectorants and antibiotics) to make the removal of secretions easier.

Similar symptoms

Difficulty breathing may be confused with rapid breathing (tachypnea). It is important to note that horses tend to naturally increase their respiratory rate under specific circumstances.  Temporary tachypnea is perfectly normal when horses are hot, excited, or after recent exercise.

Associated Symptoms

• Cough • Nasal discharge • Flared nostrils • Reduced exercise tolerance • Fever