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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 102/3/1071    most recent 00264.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Deaton, C. M. Articles by Marlin, D. J. Search for Related Content PubMed PubMed Citation Articles by Deaton, C. M. Articles by Marlin, D. J.

Early onset airway obstruction in response to organic dust in the horse

¹Department of Physiology, Animal Health Trust, Kentford, United Kingdom; ²Hartpury College, Hartpury, Gloucester, United Kingdom; ³School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin, Ireland; ⁴Department of Veterinary Clinical Sciences, Royal (Dick) School of Veterinary Studies, Easter Bush, Midlothian, United Kingdom

Submitted 1 March 2006 ; accepted in final form 12 October 2006

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 cmH₂O·l^–1·s (mean ± SE) to 1.23 ± 0.20 cmH₂O·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 cmH₂O·l^–1·s) than in the RAO group (–0.49 ± 0.04 cmH₂O·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.

equine; lung function; allergen