DAIRY FARMERS HAVE INCREASED METHACHOLINE BRONCHIAL RESPONSIVENESS INDEPENDENT OF SENSITIZATION TO MOLD ANTIGENS

Patients with farmer's lung disease (FLD) and dairy farmers have nonsp ecific bronchial hyperresponsiveness. To examine the factors determini ng bronchial hyperresponsiveness among dairy farmers, we studied airwa y functions, airway responses to inhaled methacholine, serum total IgE levels, and antigen-specific IgE levels in 37 dairy farmers and 11 lo cal control subjects. The 37 dairy farmers consisted of three groups; 12 farmers with episodes of FLD (FLD group), 13 farmers with serum ant ibody to Micropolyspora faeni(MF) and/or Thermoactinomyces vulgaris CN ) but without episodes of FLD (Ab(+) group), and 12 farmers without se rum antibodies to MF and TV and without episodes of FLD (Ab(+) group). Pulmonary function tests showed small airways disorders among farmers (each of the three groups versus control subjects; p < 005). Methacho line provocation test, utilizing PD(35)Grs (a cumulative dose of metha choline that induces 35% reduction in respiratory conductance [Grs]), showed bronchial hyperresponsiveness in each group of dairy farmers co mpared with that in control subjects (Log PD(35)Grs, mean +/- SEM: 1.2 2 +/- 0.18, 1.00 +/- 0.17, and 1.20 +/- 0.20, respectively, versus 2.1 0 +/- 0.09; p < 0.001). However, there was no statistically significan t difference in bronchial responsiveness among the three groups of dai ry farmers. In addition, there was no significant difference in serum total IgE levels and specific IgE antibodies among the four groups. Th ese results suggest that the bronchial hyperresponsiveness to methacho line among dairy farmers is not due to past episodes of FLD or sensiti zation to MF and/or TV but is possibly due to the occupational environ ment of dairy farming.