Q: What are the most common early signs of respiratory disease in horses, and how can I catch them before they get worse?

A: Three signs of respiratory disease in horses are nasal discharge, cough, and an increase in respiratory rate and/or change in depth of breathing. Nasal discharge can be watery (serous), white, or yellow (pus) with varying thickness, or can be bloody. Observe your horse’s nasal discharge on a regular basis to determine if it occurs only in one nostril or both. If the nasal discharge always happens in only one nostril, it indicates an upper airway problem rostral (toward the front of the body) to the pharynx. If the discharge occurs from both nostrils, the problem might be in either the upper airway or the lower airway. Infectious upper airway disease can also cause enlarged lymph nodes located under the throat and jaw.

Horses with respiratory disease might cough in an occasional short hack or in a deep cough characterized by an abdominal effort. It can be nonproductive (dry) or productive. Productive coughing is characterized by the occurrence of nasal discharge after coughing or the horse swallowing. Coughing repeatedly at the beginning of exercise often indicates asthma, however veterinarians should also consider infectious disease in these cases.

Your Horse’s Vital Signs and Respiratory Disease

The normal respiratory rate of a horse at rest is eight to 16 breaths per minute and can be determined by watching the horse’s lower flank or rib cage. An increase in respiratory rate not associated with disease occurs with high environmental temperatures, pain, stress, or exercise. When taking your horse’s respiratory rate, observe the length and depth of his inhalation and exhalation. An increase in the effort and duration of exhalation signifies lower respiratory disease, while an increase in (effort and duration of) inhalation might indicate an obstructive lesion in the upper airway. Horses with respiratory disease might also have a prolonged recovery of the respiratory rate after exercise. Those with severe disease might present with short, shallow but rapid respirations.

Other signs of respiratory disease include an increased heart rate, increased body temperature, decreased appetite, and reluctance to work. Horses with respiratory problems might also make abnormal sounds associated with breathing (grunting or wheezing).

Take-Home Message

Nasal discharge, coughing, or changes in breathing rate can all point to respiratory disease in horses. Watch whether discharge comes from one or both nostrils, note cough type, and track breathing effort and recovery after exercise. These clues help your veterinarian distinguish between upper vs. lower airway problems—prompting timely treatment to keep your horse healthy and comfortable.