Difference between revisions of "Summer Pasture-Associated Recurrent Airway Obstruction"

Revision as of 11:58, 26 August 2010

(SPA-RAO)

Also known as: Summer Pasture-Associated Obstructive Pulmonary Disease, Summer Pasture-Associated Heaves

Description

Summer Pasture-Associated Recurrent Airway Obstruction(SPA-RAO) is an inflammatory condition of the lower airways affecting pasture-kept horses. This is in contrast to Recurrent Airway Obstruction that affects horses that are stabled. The disease is characterised by airway inflammation, increased airway mucus production, reduced mucociliary clearance and bronchoconstriction. It occurs most commonly in the South of the United States but has also been reported in the United Kingdom.

Signalment

The average age of onset of SPA-RAO is 9 years of age. There is no reported sex predilection but Quarter Horses are over-represented.

Pathogenesis

The pathogenesis of the disease is largely unknown but suggested hypotheses include inhaled pollens or outdoor moulds or ingestion of a pasture-derived pneumotoxin.

Clinical signs

Clinical signs are similar to those associated with RAO but occur in horses kept out at pasture during the summer months, usually for more than twelve hours a day. Signs may include exercise intolerance, cough (often productive), dyspnoea, increased expiratory effort, nasal discharge and flared nostrils. Pyrexia may be a feature if a seconday bacterial infection has occurred in the airways. In severe cases, affected horses stand with their neck arched and elbows abducted. An abdominal 'heave' line may also be visible due to hypertrophy of the external abdominal oblique muscles. Lung field auscultation reveals fine crackles and wheezes. In severe cases, wheezes may be audible without a stethoscope.

Diagnosis

Diagnosis is usually based on the characteristic and seasonal appearance of clinical signs combined with a history of exposure to pasture during late spring or summer. Endoscopy may be used in order to evaluate the airways and to examine the presence of inflammation or mucus. A sample of the mucus may be taken in order to perform bacterial culture or cytology. Thoracic radiology is not commonly performed but may reveal in increased bronchointerstitial pattern.

Treatment and management

Affected horses should only be allowed access to pasture during late autumn, winter and early spring. They should ideally be kept stabled in a dust-free environment such as a stable with rubber matting and no bedding. If hay appears to act as a trigger to the horse, a complete pelleted diet may be fed or alternatively hay should be soaked. Alfalfa has been previously associated with less respiratory problems than grass hay and may be preferable.

In some cases, the response to environmental management may be significant and drug treatment may not be required. In other cases, drug therapy may be required to suffiently manage the clinical signs. Corticosteroids may be administered via nebuslisation using an inhaler in order to allow the maximum concentration of the drug in the respiratory tract, with minimal systemic side effects. This can be combined with a bronchodilator such as clenbuterol Antibiotics may be required if seconday bacterial infection is present.

References

McGorum, B. C., Edward Robinson, N., Dixon, P. M., Schumacher, J. (2007) Equine respiratory medicine and surgery Elsevier Health Sciences
Orsini, J. A., Divers, T. (2007) Equine Emergencies: Treatment and Procedures Elsevier Health Sciences

@@ Line 5: / Line 5: @@
 ==Description==
-Summer Pasture-Associated Recurrent Airway Obstruction(SPA-RAO) is an inflammatory condition of the lower airways affecting pasture-kept horses. This is in contrast to Recurrent Airway Obstruction that affects horses that are stabled and fed hay. The disease is characterised by airway inflammation, increased airway mucus production, reduced mucociliary clearance and bronchoconstriction. The disease occurs most commonly in the South of the United States.
+Summer Pasture-Associated Recurrent Airway Obstruction(SPA-RAO) is an inflammatory condition of the lower airways affecting pasture-kept horses. This is in contrast to Recurrent Airway Obstruction that affects horses that are stabled. The disease is characterised by airway inflammation, increased airway mucus production, reduced mucociliary clearance and bronchoconstriction. It occurs most commonly in the South of the United States but has also been reported in the United Kingdom.
 ==Signalment==
-The average age of onset of SPA-RAO is 9 years of age. There is no reported sex predilection but Quarter Horses are overrepresented.
+The average age of onset of SPA-RAO is 9 years of age. There is no reported sex predilection but Quarter Horses are over-represented.
 ==Pathogenesis==
@@ Line 17: / Line 17: @@
 ==Diagnosis==
-Diagnosis is usually pased on the characteristic clinical signs combined with a history of seasonal occurrence and exposure to pasture during late spring or summer. Endoscopy may be used in order to evaluate the airways and to examine the presence of inflammation or mucus. A sample of the mucus may be taken in order to perform bacterial culture or cytology.
+Diagnosis is usually based on the characteristic and seasonal appearance of clinical signs combined with a history of exposure to pasture during late spring or summer. Endoscopy may be used in order to evaluate the airways and to examine the presence of inflammation or mucus. A sample of the mucus may be taken in order to perform bacterial culture or cytology. Thoracic radiology is not commonly performed but may reveal in increased bronchointerstitial pattern.
 ==Treatment and management==
-Affected horses should only be allowed access to pasture during late autumn, winter and early spring. If hay appears to act as a trigger to the horse, a complete pelleted diet may be fed or alternatively hay should be soaked. Alfalfa has been previously associated with less respiratory problems than grass hay and may be preferable.
+Affected horses should only be allowed access to pasture during late autumn, winter and early spring. They should ideally be kept stabled in a dust-free environment such as a stable with rubber matting and no bedding. If hay appears to act as a trigger to the horse, a complete pelleted diet may be fed or alternatively hay should be soaked. Alfalfa has been previously associated with less respiratory problems than grass hay and may be preferable.
+In some cases, the response to environmental management may be significant and drug treatment may not be required. In other cases, drug therapy may be required to suffiently manage the clinical signs. Corticosteroids may be administered via nebuslisation using an inhaler in order to allow the maximum concentration of the drug in the respiratory tract, with minimal systemic side effects. This can be combined with a bronchodilator such as clenbuterol
+Antibiotics may be required if seconday bacterial infection is present.
-Horse should be kept stabled in a dust-free environment such as a stable with rubber matting and no bedding. Antibiotics may be required if seconday bacterial infection is present.
-In some cases, the response to environmental changes and conservative management may be significant and drugs may not be required.
-In other cases, drug therapy may be required to suffiently manage the clinical signs. Corticosteroids may be administered via nebuslisation using an inhaler in order to allow the maximum concentration of the drug in the respiratory tract, with minimal systemic side effects. This can be combined with a bronchodilator such as clenbuterol
 ==References==
 *McGorum, B. C., Edward Robinson, N., Dixon, P. M., Schumacher, J. (2007) '''Equine respiratory medicine and surgery''' ''Elsevier Health Sciences''