Respiratory disease in horses

Epidemiology of respiratory problems

Respiratory diseases can be considered as the second most common cause of loss of performance in sport horses and racehorses after musculoskeletal problems. The overall prevalence of respiratory diseases is most probably underestimated due to the fact that some chronic forms of diseases may develop sub clinically, although they still impede performance.

Lower Airway issues

Intensive training, repeated transports and mingling during competitions may also promote the development and transmission of infectious diseases. Whatever the type of sport, most lower airway diseases cause a significant decrease in athletic parameters and delayed cardio-respiratory recovery. The main lower respiratory diseases involved in poor performance reported are inflammatory airway disease (IAD), recurrent airway obstruction (RAO), exercise induced pulmonary haemorrhage (EIPH) and viral or bacterial infections. Several factors inevitably promote the occurrence of inflammatory diseases, such as age (higher prevalence in older individuals), pollution and other environmental conditions. Horses are often housed indoors in buildings were ventilation within the boxes is limited, indoor storage of hay and straw can be encountered and doors and windows are often closed during the cold months. This type of management promotes chronic respiratory inflammation.

Intensive training, repeated transports and mingling during competitions may also promote the development and transmission of infectious diseases.

Moreover, competition itself is also a key factor in the prevalence of lower airway diseases in horses. Competition may trigger metabolic and hormonal alterations, which disturb immunity. Depression of the immune system and the occurrence of repeated inflammatory and oxidative processes during training and competitions seem to create favourable conditions to the outbreak of infectious respiratory diseases. These respiratory problems are often subclinical but have an impact on performance and may impede the pursuit of their physical preparation as well as post-race short and long-term recovery.

Exercise Induced Pulmonary Haemorrhage (EIPH)

Exercise-induced pulmonary haemorrhage (EIPH) is a unique respiratory condition that results in the shedding of blood in the lungs and airways after a sufficient strenuous exercise. Pulmonary haemorrhages have been shown to be associated with pulmonary inflammation and fibrosis, gas exchange disturbances during exercise and subsequent poor performance. EIPH can also affect negatively the duration of the career of sport horses and race horses.


In practise, the diagnosis is generally made by observation of:

POST-EFFORT EPISTAXIS (bleeding from the nose)


However, in most cases, the blood remains within the lungs and diagnosis can only be made through sampling of the lower airways.


RACE HORSES: Prevalence as high as 95% has been reported.

EVENTING, POLO, AND EVEN HIGH-LEVEL SHOW-JUMPERS: In all disciplines including intense or fast bouts of exercise, horses have been diagnosed with EIPH. Recent study revealed that the incidence of EIPH in show-jumpers – participating at 4 and 5 star competitions – can go up to 50%.


Risk Factors

  • Age and gender
  • Type and distance of the race
  • Intense or fast bouts of exercise
  • Hardness of the ground and presence of jumps
  • Air temperature
  • Pulmonary inflammation

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