Peer-reviewed veterinary case report
Early onset airway obstruction in response to organic dust in the horse.
- Journal:
- Journal of applied physiology (Bethesda, Md. : 1985)
- Year:
- 2007
- Authors:
- Deaton, Christopher M et al.
- Affiliation:
- Dept. of Physiology · United Kingdom
- Species:
- horse
Plain-English summary
This study looked at how horses with equine recurrent airway obstruction (RAO), a condition similar to asthma in humans, respond to inhaling dust from hay. Researchers tested six RAO-affected horses that were not showing symptoms and six healthy control horses by having them breathe in a mist of hay-straw dust. They found that the healthy horses showed immediate changes in their lung function, indicating a protective response to the dust, while the RAO horses did not show these changes. This suggests that RAO horses may lack an early protective response to inhaled dust, which could make them more vulnerable to breathing problems. Overall, the treatment did not work for the RAO horses in terms of showing an early-phase response.
Abstract
Equine recurrent airway obstruction (RAO) has been used as a naturally occurring model of human asthma. However, it is unknown whether there is an early-phase response in RAO. The aim of this study was to determine whether exposure to organic dust induces immediate changes in lung function in RAO-affected horses, which could be mediated by airway mast cells. Six RAO-affected horses in remission and six control horses were challenged with hay-straw dust suspension by nebulization. Total respiratory resistance at 1 Hz, measured by forced oscillation, was increased from 0.62 +/- 0.09 cmH(2)O.l(-1).s (mean +/- SE) to 1.23 +/- 0.20 cmH(2)O.l(-1).s 15 min after nebulization in control horses (P = 0.023) but did not change significantly in the RAO group. Total respiratory reactance at 1 Hz (P = 0.005) was significantly lower in the control horses (-0.77 +/- 0.07 cmH(2)O.l(-1).s) than in the RAO group (-0.49 +/- 0.04 cmH(2)O.l(-1).s) 15 min after nebulization. Bronchoalveolar lavage fluid (BALF) histamine concentration was significantly elevated 10 and 20 min postnebulization in control horses but not in RAO horses. Minimum reactance at 1 Hz in the early postnebulization period significantly correlated with both prechallenge BALF mast cell numbers (r = -0.65, P = 0.02) and peak BALF histamine concentration postnebulization (r = -0.61, P = 0.04). In conclusion, RAO horses, unlike human asthmatic patients, do not exhibit an early-phase response. However, healthy control horses do demonstrate a mild but significant early (<20 min) phase response to inhaled organic dust. This response may serve to decrease the subsequent dose of dust inhaled and as such provide a protective mechanism, which may be compromised in RAO horses.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/17158251/