Precipitins against microbes in mouldy hay in the sera of farmers with farmer's lung or chronic bronchitis and of healthy farmers.

The aim of this study was to determine which precipitins against four antigens in 2,440 farmers are associated with the occurrence of farmer's lung (FL). The antigen panel consisted of mycelial antigens of Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus and Aspergillus umbrosus. As reference groups we used healthy farmers and those with chronic bronchitis. For the occurrence of precipitins against the four antigens there was a statistically significant difference between farmers with FL and healthy farmers but not between farmers with chronic bronchitis and healthy farmers. In a stepwise logistic linear regression analysis, farmers with FL and chronic bronchitis were compared to healthy farmers with respect to precipitins to the four antigens. Precipitins against Thermoactinomyces vulgaris differentiated farmers with FL (p less than 0.05) but not farmers with chronic bronchitis from healthy farmers. In Finland the occurrence of FL seems to be associated mainly with precipitins against Thermoactinomyces vulgaris, not with precipitins against Micropolyspora faeni as in Great Britain, and not with precipitins of Aspergillus umbrosus, which occurred most frequently in the sera of Finnish farmers. This association is in accordance with the exposure to spores of airborne moulds in farmers' work environment, where spore concentrations of Thermoactinomyces vulgaris have been measured to be about six times higher than those of Micropolyspora faeni.