Inflammatory Airway Disease (IAD) in Horses

Key Takeaways

Inflammatory airway disease (IAD) is an inflammatory condition that  affects a horse's lower respiratory tract. 

• Common clinical signs of IAD include chronic cough, decrease in performance, and nasal discharge

• Symptoms of IAD do not present when the horse is at rest, which distinguishes it from recurrent airway obstruction

• A number of factors are associated with development of IAD, including allergies, inhalation of dust, recurrent lung stress, poor air quality, and viral respiratory infections

• IAD is diagnosed based on physical examination and specialized testing to assess lung function 

• Treatment primarily involves environmental changes to reduce exposure to irritants

• Some horses require long-term administration of aerosolized bronchodilator or anti-inflammatory medication or systemic corticosteroids

A Closer Look: What is Inflammatory Airway Disease in Horses?

Inflammatory airway disease is a common condition in horses, affecting up to 50% of athletic horses. It is one of the most common causes of decreased performance in horses. IAD is generally not an emergency, however, veterinary attention is warranted. If left untreated, IAD may worsen. With proper treatment and management, prognosis is good, with most animals being able to maintain an athletic career.

Risk Factors

Certain situations can increase the severity of IAD symptoms. These include:

Transport: long-distance transport increases the chances of prolonged inhalation of dust, which, coupled with stress, increases the likelihood of IAD symptoms developing.

Intense exercise: vigorous exercise causes deep breathing. If the animal routinely exercises in temperate climates, cold or dry air can enter the lower respiratory tract causing more severe IAD symptoms. 

Environmental management: living environment is a large contributing factor in IAD symptom severity. Poorly ventilated stables increase the presence of dust, causing significant irritation and more severe symptoms.

Possible Causes

The precise causes of inflammatory airway disease are unknown. Potential causes and risk factors of inflammatory airway disease include: 

• Allergic airway disease • Recurrent lung stress • Deep inhalation of dust • Pollutants in the air 

• Persistent respiratory viral infections • Previous bacterial infections in the airways

• Episodes of exercise-induced pulmonary hemorrhage irritating the airway

Main Symptoms

Common symptoms of equine inflammatory airway disease:

• Chronic cough, particularly while the horse is eating or while warming up for exercise

• Nasal discharge • Poor performance • Exercise intolerance 

Symptoms of inflammatory airway disease typically occur during exercise, and rarely occur at rest. This distinction separates IAD from the more severe form of equine asthma, recurrent airway obstruction.

Testing and Diagnosis

IAD may be suspected based on poor performance and a physical examination. Further diagnostics are needed to confirm the diagnosis. Diagnostic tools include: 

• Rebreathing examination to assess lung sounds more clearly • Endoscopy  • Lung function test 

• Bronchoalveolar lavage • Lung biopsies

Steps to Recovery

Treatment varies in accordance with the severity of inflammation. Many horses respond to environmental changes alone. 

Management of IAD includes:

• Feeding soaked or steamed hay • Minimizing environmental dust • Increasing frequency/duration of turnout 

In some cases, medications are required to help control IAD symptoms. Treatment options include: 

• Aerosolized bronchodilator therapy • Systemic corticosteroid therapy • Inhaled anti-inflammatory medications

Prognosis for horses affected with IAD is good. With proper treatment and long-term management, most animals can maintain an athletic career. Left untreated, IAD may progress with worsening symptoms.

Prevention

IAD is not contagious in and of itself. Viral respiratory infections that are contagious may be a predisposing factor to the development of IAD. IAD often presents after a viral respiratory disease. Isolating horses presenting symptoms of viral respiratory infections decreases the probability of the disease spreading. 

Environmental management strategies to reduce exposure to dust help minimize symptoms of IAD. Strategies include feeding damp hay, keeping stables clean, and increasing turnout.

Is Inflammatory Airway Disease Common in Horses?

Inflammatory airway disease is a very common condition that affects up to 50% of athletic horses. IAD is one of the most common causes of decreased athletic performance in horses.

Typical Treatment

• Aerosolized bronchodilator therapy • Systemic corticosteroid therapy • Inhaled anti-inflammatory medications

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