Chronic obstructive pulmonary disease in the horse. 1: Nature of the disease.

This study examines chronic obstructive pulmonary disease (COPD) in horses, focusing on the cause, physical changes, pathology, and symptoms associated with the disease. The researchers identified the disease as a hypersensitivity of the horse’s respiratory system to poor quality hay and straw, identifying Micropolyspora faeni as the main agent of the disease in the northern United Kingdom.

Nature of the Disease

In this discussion, the researchers delved into the intricacies of the ailment:

• Aetiology – The study identified low-quality hay and straw as major triggers of the disease in horses. They discussed how consumption of these triggers causes a hypersensitivity reaction in the respiratory system of the affected horses.
• Pathophysiological changes – The major changes associated with this disease are airway spasms and bronchiolitis of the small airways. These changes affect the animal’s ability to breathe normally.
• Pathology – The study further identified Micropolyspora faeni, a type of fungus commonly found in hay, as the chief pathogen responsible for the disease in Northern UK. However, the leading pathogen may differ in other regions.
• Clinical Signs – The report highlighted that the disease could begin abruptly or slowly and subtly. Common symptoms were identified, although the particular disease process is reversible if the source of the antigen (the hay or straw) is removed or replaced with higher quality feed.

Diagnosis and Prognosis

The research identifies increased intrathoracic pressure and abnormally low arterial oxygen pressure as key indicators of the disease, particularly in early cases. These measurements can be recorded even in horses not showing symptoms if they have been exposed to an appropriate antigen or poor quality hay or straw about 4 to 5 hours before assessment. Thus, this provides an effective diagnostic tool in suspected cases. Additionally, the study confirmed that the disease process is reversible if the source of the antigen is removed, indicating a generally favourable prognosis with the proper management.

Further Research Suggestions

In conclusion, this study has provided a comprehensive examination of equine COPD, however, the authors suggest that further research should include:

• Investigation into other primary agents of the disease in areas outside the Northern UK, to fully understand the geographical distribution and variation of the disease.
• In-depth examination of other diagnostic methods available to clinicians, to ensure early detection and effective management of the disease.
• A broader study on the exact relationship between exposure to low-quality hay and straw and the onset of the disease, to better understand the pathogenesis of COPD in horses.