What is Heaves/COPD (Chronic Obstructive Pulmonary Disease)

COPD is the most common chronic lung disease of horses in Britain and Ireland. The reason for this is mainly due to the considerable amount of time horses spend indoors in this part of the world. More specifically it is because the usual forage and bedding (hay and straw) sometimes saved under damp and cold conditions contain factors that irritate the horses lungs leading to the signs that are characteristically associated with the disease.

How does my horse bedding and/or forage make my horse sick?

Forage and bedding materials that are saved in poor conditions are prone to overheating during storage. This can then lead to the growth of certain micro-organisms. Specifically COPD is a lung allergy to inhaled dust particles especially those containing spores of certain bacteria. Also associated with this disease is the fungus Aspergillus fumigatus. Loosely we can term the causative material as ?¢‚ǨÀúmoulds’, which appear abundantly in poorly conserved forage and bedding. When this material along with inhaled endotoxin enters the airways of the horse (especially those with more sensitive airways) it can lead to inflammation.

Are there any other factors associated with COPD in horses?

The destruction of cilia (the airways are lined my millions of hairlike projections called cilia ) is also a noteworthy factor as the hair like projections on the lining of the lung helps clear the lungs of foreign/unwanted material. In addition, boncho-spasm of airway muscles (not dissimilar to Asthma) can further lead to airway constriction and in some cases complete obstruction. Some horses have a history of suffering from respiratory infection(s) which may result in the initial compromise of the lung tissue allowing these irritants to cause COPD.

What are the typically expected clinical signs to expect with COPD?

1. Coughing is the most sensitive indicator of lung disease in horses and is the commonest presenting sign (~85% incidence) in COPD cases.
2. A nasal discharge is often noted (~55% cases). All cases of COPD have an increase in production of respiratory secretions in their lower airways. This discharge isn’t always evident as some horses swallow what is brought up before it is evident on the nostrils. Whereas others only have a discharge when they lower their head or when they cough.
3. An increase in resting breathing rate that can be over 20 breaths per minute. This can be with or without an exaggerated abdominal expiratory effort or “heave”.
4. Sometimes a rattling sound can be heard over the trachea at the approx entrance to the thoracic cavity. This is likely to be respiratory secretions moving with respect to inspiration and expiration

What if typical clinical signs are not conclusive in diagnosis of COPD?

Mildly affected animals may show only a few of the above-described signs and thus there may be insufficient clinical signs. Other tests that can aid diagnosis include bronchoscope examination of the lungs and/or tracheal secretion cytology as well as broncho-alveolar lavage fluid cytology.

What are the treatments available when a diagnosis has been made?

This disease is usually reversible even in long standing cases but only when the instigating cause has been determined and thus avoided. This usually involves removing hay and straw from the environment when the horse is kept. Where possible the horse should be permanently kept outdoors without any supplementary hay.

My horse can’t be kept outside all the time what can be done in cases like this?

If your horse has to be kept indoors then three inter-related aspects of management should be adhered to.

1. Forage:
   1. Switch to a different source of forage, e.g. silage. Even soaked hay will have some spores that can be inhaled (despite extreme care) leading to breakdowns in the management of COPD and thus cases are a result of this. Remember soaked hay will drip onto the bedding and once dry spores will hatch and more of the causative agent will be present not less.
   2. Horses like silage despite what people will tell you, it merely takes a little time to get used to. Not only that it is often more nutritious than hay. However any soiled silage should be discarded, the potential for botulism is higher with silage than with other feedstuffs.
2. Bedding
   1. Alternatives to straw such as wood shavings sawdust shredded paper or peat should be used.
   2. These must be kept dry as they also contain cellulose and can develop fungal growth if allowed to become damp.
3. Stabling
   1. In general British stables are too small and poorly ventilated. Half doors of stables should be permanently open and the back wall of stables should have an air inlet of 0.5 sq metres/horse and also if possible a roof vent of 0.15 sq metres/horse.
   2. Forage for horses should never be kept lofts etc above stables.

What medical treatments can be used to speed up recovery once a diagnosis has been reached?

Partial and temporary clinical improvement can be obtained with NSAID’s and corticosteroids, the later non specifically decrease the lung inflammation of COPD. Drugs of this nature (steroids) can be inhaled or taken orally like prednisilone, which is usually administered at 1mg/kg/day. However they should be used with caution and under specific veterinary guidance as the potential for laminitis is considerably higher with this group of drugs

Bronchodilatory drugs such as clenbuterol give immediate temporary and partial relief by relaxing the spasming muscle in affected airways and by increasing mucus clearance. However they do not relieve bronchiolar inflammation, thus a combination of both drug groups may be required initially to resolve or improve clinical signs.

This entry was posted on Thursday, September 6th, 2007 at 9:50 pm and is filed under Veterinary articles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.