What is Chronic Obstructive Pulmonary Disease ?
Also known as reactive airway disease or RAO, or simply as heaves, chronic obstructive pulmonary disease leads to coughing and discharge from the nose of horses. In later stages of the illness, horses sometimes have a hard time breathing and their chest and abdomen will be noticed moving as a result of the struggle. In the disease, which is common, the bronchioles and alveoli in the lungs of the horse are impacted due to an allergy to dust particles and spores that the horse has breathed in. Some horses have limited resistance and their airways are blocked upon being exposed to allergens. The average age of onset for the disease is nine years old.
Chronic obstructive pulmonary disease, also known as recurrent airway obstruction, occurs when a horse is exposed to an allergen that causes swelling in their small airway, leading to coughing, discharge and breathing difficulty.
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Symptoms of Chronic Obstructive Pulmonary Disease in Horses
Early in the course of the disease you might only see a small amount of discharge from your horse’s nose or he may have a dry cough. Without treatment, your horse may struggle when expected to move more quickly and his cough may become more pronounced. Upon disease progression he will start to cough even with minimal exercise.
In many cases, the symptoms that your horse will experience will be minimal for years, progressing slowly as he ages. Some horses will suffer sudden attacks that are linked to recurring exposure to dust or pollen; the illness may be seasonal or linked to the conditions in the stable where he lives or to the food that he eats.
Upon the disease progressing in severity, your horse may struggle to breathe even when resting. His respiratory rate will increase and it will require a lot of effort for him to breathe. Horses that have been ill for a long time have to make such significant effort to breathe (using their chest and stomach muscles) that they are “heaving”.
In early cases, the only symptom that may be seen is a small amount of discharge from your horse’s nose and a dry cough. In severe cases, your horse may struggle to breathe even when at rest.
Causes of Chronic Obstructive Pulmonary Disease in Horses
The majority of horses will display symptoms of chronic obstructive pulmonary disease when they reside in a stable, are fed hay and have straw bedding. Fungal spores (found in hay, straw, feed and moldy bedding) and dust from pollen are the most likely triggers of the illness. It is thought that prior viral and bacterial infections in the lung can cause a horse to be more susceptible to the illness.
When your horse has an allergic reaction his airways will produce fluid and the walls of the small airways in his lungs will increase in thickness. This will cause the obstruction and lead to your horse having to work harder to breathe. He will also begin coughing in an effort to clear out the mucus that is trapped.
Should your horse show symptoms of chronic obstructive pulmonary disease, he will have developed an allergy to dust, spores or pollen (or all three) that has been inhaled. When there is more pollen in the air, your horse’s condition will worsen; thus it is important to maintain good air quality in your horse’s stable. While the disease is not more likely to develop in a particular gender or breed, how susceptible a horse is to the condition may be inherited.
Diagnosis of Chronic Obstructive Pulmonary Disease in Horses
Your veterinarian will conduct a full examination of your horse and will ask you about the symptoms that you have noticed, when you first noticed them, and any changes in the symptoms over time. If your veterinarian is not familiar with your horse’s medical history he will inquire about that as well. Typically, diagnosis will be made based on your horse’s history and what is seen during the examination. Your veterinarian may take radiographs of your horse, and if there is no response to standard treatment after 14 days, your veterinarian may conduct thoracic radiographs in an effort to identify another possible diagnosis (interstitial pneumonia, pulmonary fibrosis, bacterial pneumonia). Endoscopy, as well as collecting samples to be examined under a microscope, may also help to eliminate other causes of chronic cough and confirm the diagnosis of chronic obstructive pulmonary disease.
Treatment of Chronic Obstructive Pulmonary Disease in Horses
It is important that you maintain your horse’s environment to reduce his exposure to the allergen that is affecting him. While most horses will do better in a pasture, should that not be an option their stall should be dust free. Should your horse’s disease be linked to the pasture in the summer, it will be best for him to be in a stable that is free of dust. Other ways to help your horse include:
- Provide commercial feeds or low allergen sources of roughage
- Provide him with paper bedding
- Should he be in a stall, the stall should not be connected to an indoor arena
- Hay should not be stored above your horse’s stall
- If impacted by pollens your horse should be removed from high pollen areas until the end of the season
For more severe conditions or for those horses who have had the condition for a long time, medication may be necessary. The following medications may be considered by your veterinarian:
- Bronchodilators (clenbuterol or cromoglycate) will dilate the airways
- Corticosteroids to help with the allergic reaction
- Allergy desensitization treatments
Recovery of Chronic Obstructive Pulmonary Disease in Horses
Based on the nature of the disease that takes place in the lungs of your horse, the condition is not reversible (with the possible exception of the very early stages). The condition is progressive and while it cannot be cured, its progression can be slowed or stopped.
Many horses with the condition show symptoms when residing in a stable, ingesting hay and sleeping on straw. Removing these items will often lead to the elimination or reduction of symptoms. Managing your horse’s environment is the best thing you can do for him to alleviate symptoms of his condition and help him to live more comfortably.