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  • Author or Editor: Ralph E. Beadle x
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Abstract

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.

Animals—19 horses with SPA-RAO and 10 nonaffected horses.

Procedures—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 and Clinical Relevance—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.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare responses of bronchial rings obtained from healthy horses and horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) to selected mediators of airway hyperreactivity in vitro.

Sample Population—Bronchial rings from 6 healthy horses and 6 horses affected with SPAOPD.

Procedure—Bronchial rings obtained from each group of horses were mounted in organ baths and attached to force transducers interfaced with a polygraph. After applying 2g of tension, each ring was allowed to equilibrate for 45 minutes in Tyrode's solution at 37 C. Cumulative concentration-response relationships to graded concentrations of selected mediators (10–8 to 10–4 M ) were determined and analyzed for significance at each concentration.

Results—Acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4 induced concentrationdependent contractile responses in bronchial rings. Prostaglandin F induced weak and inconsistent contractile responses. The other 2 agents, norepinephrine and substance P, did not induce concentrationdependent responses. Considering the overall groupdrug effect, acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4 were effective in inducing consistent concentration-dependent contractile responses in both groups. Only 5-hydroxytryptamine and histamine induced significant responses in contractility between groups. The response of bronchial rings from horses with SPAOPD to 5-hydroxytryptamine was significantly greater than those from control horses, whereas the response to histamine was significantly lower. Significant responses were evident at concentrations ranging from 10–6 to 10–4 M for both drugs.

Conclusions and Clinical Relevance—Because the airways of horses with SPAOPD had increased responsiveness to 5-hydroxytryptamine in vitro, treatment modalities using 5-hydroxytryptamine antagonists should be investigated to address this phenomenon. (Am J Vet Res 2001;62:259–263).

Full access
in American Journal of Veterinary Research

Abstract

Objective—To correlate clinical score, intrapleural pressure, cytologic findings of bronchoalveolar lavage fluid (BALF), and histologic lesions of pulmonary tissue in horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD).

Animals—8 adult horses affected with SPAOPD and 6 adult horses without evidence of respiratory tract disease.

Procedure—Clinical score, change in intrapleural pressure (ΔPpl) during tidal breathing, results of cytologic examination and bacteriologic culture of BALF, and results of histologic examination of pulmonary parenchyma were evaluated.

Results—Clinical scores for SPAOPD-affected horses (median, 5.75; range, 4.0 to 7.5) were significantly greater, compared with clinically normal horses (median, 2.0; range, 2.0 to 3.0). Cytologic examination of BALF from SPAOPD-affected horses revealed predominantly nondegenerate neutrophils. Histologic lesions were identified throughout pulmonary tissue and included severe accumulation of mucus and neutrophils within the small airways, metaplasia of bronchiolar goblet cells, and mild peribronchial infiltrate. Histologic examination of specimens collected via percutaneous biopsy was predictive of disease and corresponded to findings at postmortem examination. Clinical score and δPpl were highly correlated with mucus accumulation in the airways of affected horses. Peribronchial inflammatory infiltrate correlated with percentage of neutrophils in BALF of affected horses.

Conclusions and Clinical Relevance—Clinical scoring and ΔPpl provided valid estimates of disease severity. Findings from cytologic examination of BALF of SPAOPD-affected horses varied, although, in most instances, it was diagnostically useful. Severe mucus accumulation in the airways was the most remarkable histopathologic finding in SPAOPDaffected horses. Examination of biopsy specimens collected from pulmonary parenchyma was consistently useful in diagnosing SPAOPD. (Am J Vet Res 2000;61:167–173)

Full access
in American Journal of Veterinary Research