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

Also known as: '''''SPA-RAO — Summer Pasture-Associated Obstructive Pulmonary Disease (SPAOPD)— Summer Pasture-Associated Heaves

==Description==

==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 kept in a stabled environment. SPA-RAO is characterised by airway inflammation, increased airway mucus production, reduced mucociliary clearance and bronchoconstriction in response to allergen exposure. The pathogenesis of the disease is largely unknown but suggested hypotheses include inhaled pollens or outdoor moulds, or ingestion of a pasture-derived pneumotoxin. It occurs most commonly in the southern states of America but has also been reported in the United Kingdom.

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 kept in a stabled environment. SPA-RAO is characterised by airway inflammation, increased airway mucus production, reduced mucociliary clearance and bronchoconstriction in response to allergen exposure. The pathogenesis of the disease is largely unknown but suggested hypotheses include inhaled pollens or outdoor moulds, or ingestion of a pasture-derived pneumotoxin. It occurs most commonly in the southern states of America but has also been reported in the United Kingdom.

==Signalment==

==Signalment==

==Diagnosis==

==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 examine the airways for the presence of inflammation or mucus. A sample of mucus can be obtained via bronchoalveolar lavage which often yields copious mucopurulent material. Cytology performed on the sample usually reveals >25% non-degenerate neutrophils confirming the presence of lower airway inflammation. Curschmann's spirals may also be observed, representing inspissated mucus in the obstructed lower airways.  

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 examine the airways for the presence of inflammation or mucus. A sample of mucus can be obtained via bronchoalveolar lavage which often yields copious mucopurulent material. Cytology performed on the sample usually reveals >25% non-degenerate neutrophils confirming the presence of lower airway inflammation. Curschmann's spirals may also be observed, representing inspissated mucus in the obstructed lower airways.  

Thoracic radiology is not commonly performed but often reveals an increased bronchointerstitial pattern.

Thoracic radiology is not commonly performed but often reveals an increased bronchointerstitial pattern.

Control of environmental exposure is essential in horses affected with SPA-RAO. Affected horses should only be allowed access to pasture during late autumn, winter and early spring. They should ideally be kept in a dust-free environment such as a clean stable with rubber matting and no bedding. If hay appears to act as a trigger to the horse, a complete pelleted diet can be fed or alternatively hay should be thoroughly soaked. Alfalfa hay has been previously associated with less respiratory problems than grass hay and may be a preferable source of roughage for affected horses. Horses with severely compromised respiratory function should be rested until their condition has improved.

Control of environmental exposure is essential in horses affected with SPA-RAO. Affected horses should only be allowed access to pasture during late autumn, winter and early spring. They should ideally be kept in a dust-free environment such as a clean stable with rubber matting and no bedding. If hay appears to act as a trigger to the horse, a complete pelleted diet can be fed or alternatively hay should be thoroughly soaked. Alfalfa hay has been previously associated with less respiratory problems than grass hay and may be a preferable source of roughage for affected horses. Horses with severely compromised respiratory function should be rested until their condition has improved.

In some cases, the response to environmental management may be significant and further treatment may not be required. In more severe cases, drug therapy may be required to suffiently manage the horse's condition. Corticosteroids (e.g. dexamethasone)are used in order to reduce airway inflammation and can be administered via nebuslisation using an inhaler in order to produce the maximum concentration of the drug in the respiratory tract. Minimal systemic side effects are induced with this mode of administration. This treatment can be combined with a bronchodilator such as clenbuterol to reduce smooth muscle contraction in the lower airways. Antibiotics may be required if seconday bacterial infection is present.

In some cases, the response to environmental management may be significant and further treatment may not be required. In more severe cases, drug therapy may be required to sufficiently manage the horse's condition. Corticosteroids (e.g. dexamethasone) are used in order to reduce airway inflammation and can be administered via nebulisation using an inhaler in order to produce the maximum concentration of the drug in the respiratory tract. Minimal systemic side effects are induced with this mode of administration. This treatment can be combined with a bronchodilator such as clenbuterol to reduce smooth muscle contraction in the lower airways. Antibiotics may be required if secondary bacterial infection is present.

   

   

==References==

==References==

*Lavoie, J. P., Hinchcliff, K. W. (2009) '''Blackwell's Five-Minute Veterinary Consult: Equine''' ''John Wiley and Sons''

*Lavoie, J. P., Hinchcliff, K. W. (2009) '''Blackwell's Five-Minute Veterinary Consult: Equine''' ''John Wiley and Sons''

*McGorum, B. C., Edward Robinson, N., Dixon, P. M., Schumacher, J. (2007) '''Equine respiratory medicine and surgery''' ''Elsevier Health Sciences''   

*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''

*Orsini, J. A., Divers, T. (2007) '''Equine Emergencies: Treatment and Procedures''' ''Elsevier Health Sciences''

[[Category:Allergic Respiratory Diseases]][[Category:Horse]][[Category:To Do - SophieIgnarski]]

 

[[Category:To Do - Review]]

 

[[Category:Allergic Respiratory Diseases]][[Category:Respiratory Disorders - Horse]]

[[Category:Expert Review]]