Chronic obstructive pulmonary disease (COPD)
Chronic obstructive pulmonary disease also known as summer pasture associated obstructive pulmonary disease (SPAOPD) and recurrent airway obstruction (RAO) or Heaves has been a problem for many years.
In most cases an inflammatory brochiolitis results from a hypersensitivity reaction to inhaled allergens, as well as non-allergic airway over reaction to inhaled irritants and other substances such as endotoxin. Horses commonly develop coughing, mucopurulent nasal discharge (especially when the head is lowered or after exercise) and increased expiratory effort (often with a double lift on expiration). Often there is a history of 'snot on the ground' outside the stable door in the morning. These symptoms result from bronchospasm and accumulation of airway secretions, which also cause obstruction of the airways and often an increased respiratory rate.
We can confirm the presence of the disease by taking samples from the trachea, using an endoscope, which is characterised by a marked neutrophilia.
The first consideration is the air hygiene in which your horse or pony is kept. There are four major factors: ventilation, forage, bedding and contamination (from adjacent stables, hay storage, muck heaps etc).
The majority of stables are under ventilated and professional advice should be taken when constructing or converting boxes. With the advent of efficient, modern rugs (where appropriate) there is no excuse for under ventilating stables and this can be achieved without creating and discomfort for your horse.
The availability of excellent, well-padded rubber stable matting is probably been of the greatest assistance in helping RAO in many horses. It is important that the matting is laid correctly on a sealed floor with a gentle slope and not used with bedding such as straw. In most cases no bedding should be required, then the mats can be washed daily, or a light sprinkling of shavings can be used. The matting has a fairly high initial cost but there is a considerable saving in bedding (and drug costs if your horse has RAO).
Bagged grass or haylage is now widely available and is very suitable as a non-allergic forage, however not all horses adjust to the taste or the reduced amounts that have to be fed, due to the increased nutritional value compared to hay. If you decide to feed hay to a horse that has suffered from RAO it must be soaked in water before feeding and fed at ground level to reduce the inhalation of any allergens and encourage drainage of any secretions from the lungs and trachea.
Soaking hay is a messy business unless tackled properly. I have found that the best method is to cover the hay in a large tub with water then tip the water out, leave it to drain upside down for at least half an hour then feed the hay to your horse in the same tub. Unless you wish to leach out some of the protein and carbohydrate in the hay, if your pony suffers from laminitis for example, the hay should only be soaked for 30 to 60 minutes before the water is drained off.
If environmental improvement fails to improve the RAO sufficiently then medication is used to either control the condition or help shorten the recovery time. Drugs used have included b2-agonists (e.g. Ventipulmin), mucolytics (e.g. Sputolosin) and glucocorticoids (e.g. Prednisolone) all by mouth.
Sodium Cromoglycate has been used in the past as an inhalation agent but the method of administration was, in our hands, clumsy, unreliable and ineffective and its use was discontinued.
A more practical method of administering inhaled drugs to a horse is a spacer device called a Babyhaler, designed for use in babies and children, which can be placed against a horse's nostril. In our experience this effectively administers the correct dose of drug from a metered dose inhaler, again designed for human asthmatics providing a ‘cost effective’ solution.
Metered dose inhalers are not licensed for use in horses however in selected appropriate cases we have used the Becloforte inhaler, as above, often with spectacular results, in horses that have had little response to licensed treatments. It should be born in mind however that although inhaled corticosteroids have less side effects than those given by mouth. Occasional side effects have been reported in horses whereas in humans inhaled steroids are considered to have minimal potential systemic side effects.