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Causes of Coughing & a Runny Nose in Horses

| Updated August 11, 2017

When diagnosing a horse’s cough and runny nose, veterinarians commonly look for three diseases. Chronic obstructive pulmonary disorder, bacterial pleuropneumonia and equine herpes virus all cause respiratory distress and, without proper veterinary analysis, can be easily mistaken for one another, writes veterinarian Ronald Riegel, in the “Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse.” Learning how to differentiate between these disorders helps horse owners better care for their sick animals.

Chronic Obstructive Pulmonary Disorder

A disorder found mainly in older horses kept in colder climates, chronic obstructive pulmonary disorder -- also called COPD or “heaves” -- produces chronic coughing and occasional nasal discharge in affected animals after exercise or eating. While the true cause of COPD remains unknown, veterinarians believe that a hypersensitive reaction to dust results in the inflammation of the horse’s lower airways, which characterizes the disease. Veterinary treatment typically includes the administration of corticosteroids for a limited time to relieve the inflammation, and aggressive inhalation therapy.

Bacterial Pleuropneumonia

Four species of streptococci bacteria cause pleuropneumonia in horses, usually when the animal’s immune system is compromised by stress, overwork, long-distance transport or a secondary viral respiratory infection. The most common, S. equi, results in the disease called “strangles.” Clinical signs include exercise intolerance, weight loss, coughing, fever, lethargy and nasal discharge. The term “strangles” comes from the swollen appearance of the lymph nodes at the juncture of the horse’s cheek and neck, which often abscess and burst open, releasing pus and lymphatic fluid. Treatment typically includes systemic antibiotic therapy and the administration of bronchodilators. Your veterinarian may also prescribe non-steroidal anti-inflammatory medications -- NSAIDs -- and supportive care of intravenous fluids and supplemental vitamins.

Equine Herpes Virus

Horses affected by the equine herpes virus-1 chronically cough, have runny noses, and, if pregnant, may abort the fetus. Also called rhinopneumonitis, this virus typically invades the systems of older, immuno-compromised animals, young or weak horses, and those that are stressed through overwork or exercise. The herpes virus can be quickly transferred through the air from horse to horse, and passed on the clothes and shoes of handlers. Because of its viral component, veterinarians treat the disease by providing supportive care, including the use of NSAIDs, intravenous fluids and vitamin supplements.


Horses infected with the herpes virus and any of the bacteria-causing pleuropneumonia need to be isolated from other healthy animals in the barn to keep from passing on the disease. In their paper “FAQ Equine Herpes Virus-1,” veterinarians Larry Bauman and J. Liv Sandberg of the University of Wisconsin Equine Extension Service recommend isolating sick horses for at least 21 days, and using bleach and proper hand-washing procedures to disinfect the hands and boots of their handlers. With horses diagnosed with COPD, owners should take every precaution to keep dust out of the animal’s stall or barn, even soaking the animal’s hay in water to prevent further exposure to dust.