Temporal clinical exacerbation of summer pasture-associated recurrent airway obstruction and relationship with climate and aeroallergens in horses.
OBJECTIVE
To describe the seasonal pattern of clinical exacerbation of summer pasture-associated recurrent airway obstruction (SPA-RAO) in relation to climate and aeroallergens in horses.


METHODS
19 horses with SPA-RAO and 10 nonaffected horses.


METHODS
Daily examinations were performed on all horses while they were kept on pasture for 3 years. Onset and progression of clinical exacerbation based on a clinical score of respiratory effort were evaluated in relation to changes in maximum temperature, minimum temperature, mean temperature, maximum dew-point temperature, minimum dew-point temperature, and delta dew-point temperature. Seasonal pattern of clinical exacerbation was evaluated in relation to aeroallergen counts (20 types of fungal spores and 28 types of pollen).


RESULTS
Seasonal pattern of clinical exacerbation of SPA-RAO was associated with increases in temperature (heat) and dew-point temperature (humidity), counts of fungal spores, and counts of grass pollen grains. Seasonal pattern of clinical exacerbation paralleled and was associated with increases in counts of specific types of fungal spores, particularly Basidiospore, Nigrospora, and Curvularia spp.


CONCLUSIONS
Although a causal relationship could not be determined, the seasonal pattern of clinical exacerbation of SPA-RAO was associated with hot and humid conditions and high environmental counts for fungal spores and grass pollen grains. It is not known yet whether these are aeroallergens that cause clinical exacerbation of the disease.
Costa
Lais R R
LR
Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803-8410, USA.
Johnson
Jill R
JR
Baur
Matthew E
ME
Beadle
Ralph E
RE
D000402:Airway Obstruction / Q000276:immunology / Q000662:veterinary*; D000818:Animals; D002980:Climate; D006734:Horse Diseases / Q000276:immunology*; D006736:Horses; D008145:Louisiana; D011058:Pollen / Q000276:immunology; D012130:Respiratory Hypersensitivity / Q000276:immunology / Q000662:veterinary*; D012621:Seasons; D013172:Spores, Fungal / Q000276:immunology