RESPONSES OF HORSES AFFECTED WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE TO INHALATION CHALLENGES WITH MOLD ANTIGENS

Eight control and 8 asymptomatic COPD-affected horses were given, on s eparate occasions, inhalation challenges with extracts of Micropolyspo ra faeni, Aspergillus fumigatus and Thermoactinomyces vulgaris. All ho rses were also given nebulised phosphate-buffered saline (PBS) challen ges and 'natural challenges' (NCs), i.e. exposure to hav and straw, as control challenges. Responses were assessed by clinical, pulmonary me chanics, arterial blood gas tensions, arterial blood pH and bronchoalv eolar lavage fluid cytological examinations PBS challenges had no effe ct on control or COPD-affected horses, while NC induced COPD only in t he COPD-affected horses. Pulmonary disease, similar to naturally occur ring COPD, was induced, only in the COPD-affected horses, by M. faeni and A. fumigatus challenges, thus implicating these organisms in the a etiology of equine COPD. The role of T. vulgaris in the aetiology or e quine COPD could not, however, be determined because the T vulgaris ch allenges, in addition to inducing pulmonary disease in 4 COPD-affected horses, induced pulmonary disease in 2 control horses which had been unaffected by NC. The absence of pulmonary disease in control horses a fter M. faeni, A. fumigatus and NC challenges suggests that equine COP D is a pulmonary hypersensitivity, rather than a nonspecific toxic res ponse.