Changes

===Clinical Signs===

===Clinical Signs===

Mildly affected horses generally present with a history of occasional coughing and exercise intolerance. Signs become more obvious as the disease progresses. Tachypnoea is often seen, and there may be a mucopurulent nasal discharge. Severely affected animals show signs of respiratory distress at rest. These can include flared nostrils, wheezing, paroxysmal bouts of coughing and a laboured abdominal component to expiration. Chronically, marked dyspnoea increases energy expenditure and the animal may lose condition, as well as developing a "heave line" due to hypertrophy of the external abdominal oblique muscle<ref name="one" /><ref name="six" /><ref name="eight>Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''', ''Merial''</ref>. Fever does not normally develop unless there are secondary bacterial complications.

Mildly affected horses generally present with a history of occasional coughing and exercise intolerance. Signs become more obvious as the disease progresses. Tachypnoea is often seen, and there may be a mucopurulent nasal discharge. Severely affected animals show signs of respiratory distress at rest. These can include flared nostrils, wheezing, paroxysmal bouts of coughing and a laboured abdominal component to expiration. Chronically, marked dyspnoea increases energy expenditure and the animal may lose condition, as well as developing a "heave line" due to hypertrophy of the external abdominal oblique muscle<ref name="one" /><ref name="six" /><ref name="eight">Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''', ''Merial''</ref>. Fever does not normally develop unless there are secondary bacterial complications.

On physical examination, thoracic auscultation typically reveals a prolonged expiratory phase of respiration and adventitious respiratory noises. Wheezes are most pronounced during expiration, and crackles are associated with the excessive mucus production<ref name="eight" />. However, the airways are so obstructed in some severely affected animals that there is insufficient air movement to generate audible breath sounds, and the lungs are very quiet on auscultation<ref name="one" />. In mildly affected horses a rebreathing bag can be used to aid auscultation, but this should never be performed in dyspnoeic animals<ref name="one" /><ref name="six" />. There may be an increased sensitivity of the cough reflex on tracheal compression.

On physical examination, thoracic auscultation typically reveals a prolonged expiratory phase of respiration and adventitious respiratory noises. Wheezes are most pronounced during expiration, and crackles are associated with the excessive mucus production<ref name="eight" />. However, the airways are so obstructed in some severely affected animals that there is insufficient air movement to generate audible breath sounds, and the lungs are very quiet on auscultation<ref name="one" />. In mildly affected horses a rebreathing bag can be used to aid auscultation, but this should never be performed in dyspnoeic animals<ref name="one" /><ref name="six" />. There may be an increased sensitivity of the cough reflex on tracheal compression.