Types of Equine Asthma


Types of Equine Asthma


Mild-to-Moderate Equine Asthma, previously Classified as IAD, is typically a respiratory disease that affects young to middle aged horses, as young as yearlings. Horses with Mild-to-Moderate Asthma do not show signs of respiratory difficulty at rest but may cough, have increased mucus in the trachea, and have decreased performance.This disease differs from Severe Equine Asthma, in that affected horses typically do not show increased respiratory efforts at rest.The exact cause is unknown, but is thought to be associated with inhalation of irritants such as barn dust and air pollution.


Severe Equine Asthma, previously RAO “Heaves/Broken Wind” or COPD, is a chronic airway disease that tends to be seen in older horses, usually from 6 years onwards. Horses with Severe Equine Asthma tend to have respiratory difficulty at rest, increased effort and rate of breathing, flaring of the nostrils, coughing, and mucus in the trachea and occasionally in the nostrils. Due to these difficulties associated with Severe Equine Asthma, a horse works harder to pull air into and expel air from the lungs than a healthy horse. This increased respiratory work forces the horse to use its abdominal muscles during the late phase of exhalation. Over time, the additional workload results in the visible enlargement of the abdominal muscles and the formation of what is known as a “Heave line”.

Other Equine Respiratory Conditions

EIPH in Horses

EIPH (Exercise-Induced Pulmonary Haemorrhage), also known as bleeding, is most commonly seen in horse during high-intensity competition/Exercise such as Thoroughbred/Standardbred Racing, Barrel Racing and Eventing. Horses that suffer from EIPH are known as “Bleeders”. In the majority of cases EIPH is not apparent unless an endoscopic examination of the airways is performed following exercise. However, a small proportion of horses may show bleeding at the nostrils after exercise (epistaxis). EIPH reduces a horse's racing performance. Severe EIPH shortens a horse's racing career. Moderate to severe EIPH is associated with a worsened finishing position in a race/competition. Repeated bouts of EIPH that occur with daily training may lead to more significant changes and a greater degree of tissue damage over time with consequentloss of lung function.

Respiratory Infections

Equine respiratory infections can be caused by Bacteria, Fungus or Viruses and can affect all horse from foals to the oldest and can be present in both the lower and upper respiratory system. Respiratory infections are the most common infectious diseases of horses. The acute infection in horses can incapacitate a horse anywhere from a week to a month. Symptoms of respiratory-tract infection include, nasal discharge-clear to yellow or white, coughing, lethargy poor appetite and changes in breathing pattern. Some of the most common infections include Rhodococcus equi, Streptococcus Bacterium, Aspergillus Fungus and the Equine Herpes Virus.