Farmer's lung disease in Vermont

Area of Science:

• Immunology
• Pulmonary Medicine
• Environmental Health

Background:

• Thermophilic actinomycetes are environmental microorganisms.
• Exposure to these microbes can lead to hypersensitivity pneumonitis, including farmer's lung disease (FLD).
• Antibody detection is used to assess exposure and potential disease association.

Purpose of the Study:

• To survey antibody prevalence to Micropolyspora faeni (M. faeni) and Thermoactinomyces vulgaris (T. vulgaris) in various Vermont population groups.
• To compare the precipitin method and indirect fluorescent antibody (IFA) technique for antibody detection.
• To investigate the correlation between antibody presence, specific microbial exposure, and symptoms suggestive of farmer's lung disease.

Main Methods:

• Antibodies to M. faeni and T. vulgaris were measured using the precipitin method in hospital employees, blood donors, chronic bronchitis patients, dairy farmers, and pulmonary fibrosis patients.
• M. faeni antibodies were additionally measured by the indirect fluorescent antibody (IFA) technique in 124 subjects.
• Clinical symptoms potentially related to farmer's lung disease were assessed in surveyed individuals.

Main Results:

• A good correlation was observed between the precipitin and IFA methods for M. faeni antibodies (r=0.48).
• Antibodies to thermophilic actinomycetes were uncommon in hospital employees, blood donors, and chronic bronchitis patients.
• Among dairy farmers, 5.4% had M. faeni antibodies and 1.2% had T. vulgaris antibodies. Only one farmer with M. faeni antibodies reported possible FLD symptoms, while 4.1% of precipitin-negative farmers had suggestive symptoms.
• In pulmonary fibrosis patients, 5.6% had M. faeni antibodies (5 diagnosed with FLD) and 14.4% had T. vulgaris antibodies.
• IFA testing did not improve symptom correlation, and high IFA titers were found in both symptomatic and asymptomatic individuals.

Conclusions:

• Antibody prevalence to M. faeni and T. vulgaris varies across different population groups in Vermont.
• The precipitin and IFA methods show moderate correlation for M. faeni antibody detection.
• The presence of antibodies to thermophilic actinomycetes does not strongly correlate with farmer's lung disease symptoms in dairy farmers or hypersensitivity pneumonitis in pulmonary fibrosis patients, suggesting other factors may be involved.