Chronic Obstructive Pulmonary Disease (COPD)
In equine COPD, inhalation of airborne allergens leads to airway inflammation which gives rise to bronchospasm. Treatment therefore involves prevention of exposure to allergens by environmental management, reduction of inflammation by use of corticosteroids, and relief of airway obstruction by use of bronchodilator drugs. Depending on the severity of the disease, use of the horse, and facilities available, one or all of these treatments may be used for a COPD-affected horse. There is no cure for COPD and therefore treatments need to be continued for life.
Environmental Management: The simplest way to treat a COPD horse is to change the environment so as to minimize exposure to hay dusts. This can easily be accomplished by putting the horse out to pasture. COPD-afflicted horses put out to pasture will go into clinical remission. If a horse must be stabled, then it is necessary to eliminate the use of straw for bedding and hay for feed. Even though the dust levels in the barn may seem insignificant, research has shown that the dust levels in the breathing zone (i.e., around the nose) of a horse eating hay can be as much as 30 to 40 times higher than in the rest of the stall. When a horse is eating a low-dust feed such as pellets, the dust levels in the breathing zone are equivalent to those in the stall. An effective management strategy for stabled COPD-afflicted horses, therefore, is to bed them on shavings and feed them a low-dust diet. Feeds low in dust include complete pelleted feed, alfalfa cubes, and grass silage (haylage). Horses in adjacent stalls preferably should be kept in the same manner so as to prevent hay dusts from contaminating the stall of the COPD horse. However, if this is not possible, simply changing the management in one stall can dramatically improve lung function in a COPD-affected horse. Hay should not be stored near the stall of a horse with COPD. Improving the ventilation in the barn can also help to minimize airborne particles. This may be accomplished by merely keeping the windows and doors open whenever possible or by using more sophisticated ventilation systems. It is very important to realize that very short exposure of a COPD-susceptible horse to hay dusts can initiate inflammation and airway obstruction that can last for days. One research study reported that when COPD-susceptible horses were fed hay for seven hours and then put into a low-dust environment, three days later they still had inflamed airways. For this reason, COPD-affected horses should not simply be pastured during the day and then stabled and fed hay at night. This overnight exposure to dusts will be sufficient to maintain their airway obstruction.
Anti-Inflammatory Drug Therapy.
In addition to changing the environment of a stabled COPD horse, it may be necessary to administer anti-inflammatory drugs. Corticosteroids are the drugs of choice for relieving inflammation of the airways. Corticosteroids can be administered by mouth, by injection, or by inhalation. When they are administered by mouth or by injection, therapy usually begins with a high dose; as the horse improves, the dose is reduced to a maintenance level. Inhaled steroids offer the advantage of a high dose within the airways and minimal systemic side effects, but a special mask is necessary for administration.
Bronchodilator Drug Therapy.
Bronchodilators relax airway smooth muscle and relieve airway obstruction. In mildly affected horses, they may be the first line of therapy. They can also be safely combined with anti-inflammatory drugs for treatment of more severely affected horses. This combination is beneficial because anti-inflammatory drugs can reduce airway wall thickening but have no direct effect on the smooth muscle regulating the diameter of the airways. Bronchodilator drugs can be given orally, by injection, or by inhalation. Oral administration is the most convenient method, but inhalation therapy is the most effective treatment for relief of airway obstruction. As with anti-inflammatory therapy, administration of bronchodilators by inhalation requires the use of a special mask.