CHRONIC OBSTRUCTIVE PULMONARY-DISEASE (COPD) IN HORSES - ETIOLOGICAL STUDIES - RESPONSES TO INTRADERMAL AND INHALATION ANTIGENIC CHALLENGE

Micropolyspora faeni and Aspergillus fumigatus were identified as common causes of respiratory hypersensitivity in horses affected with chronic obstructive pulmonary disease (COPD). Rye grass pollen and an Actinomycete evoked respiratory allergy in a few horses. Not infrequently, individual horses had respiratory hypersensitivity to 2 or more antigens. The methods used to examine for allergy were intradermal testing and inhalation challenge with environmental antigens. An intradermal test using an M. faeni extract was suitable for diagnostic use in horses previously accurately diagnosed as suffering from COPD. In contrast, the A. fumigatus antigen used proved unsatisfactory for such a purpose. Skin reaction to M. faeni and A. fumigatus extracts by horses affected with COPD indicated that the hypersensitivity was a dual one, a weak response shortly after injection followed by an Arthus-like response 4-8 h later. As a parameter for monitoring responses to inhalation challenge, maximum intrathoracic pressure change (max .delta. Ppl) proved satisfactory, whereas changes in partial pressure of arterial O2 (PaO2) did not.