Dairy farmers have increased methacholine bronchial responsiveness independent of sensitization to mold antigens.

Patients with farmer's lung disease (FLD) and dairy farmers have nonspecific bronchial hyperresponsiveness. To examine the factors determining bronchial hyperresponsiveness among dairy farmers, we studied airway functions, airway responses to inhaled methacholine, serum total IgE levels, and antigen-specific IgE levels in 37 dairy farmers and 11 local control subjects. The 37 dairy farmers consisted of three groups; 12 farmers with episodes of FLD (FLD group), 13 farmers with serum antibody to Micropolyspora faeni (MF) and/or Thermoactinomyces vulgaris (TV) but without episodes of FLD (Ab(+) group), and 12 farmers without serum 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 < 0.05). Methacholine provocation test, utilizing PD35Grs (a cumulative dose of methacholine that induces 35% reduction in respiratory conductance [Grs]), showed bronchial hyperresponsiveness in...