To establish the seroprevalence of antibodies to C. burnetii, Leptospira and Brucella in subjects at risk of exposure, 128 workers exposed to farm animals and 280 healthy blood donors were studied. Antibodies to C. burnetii, Leptospira and Brucella were determined by indirect immunofluorescence assay, by microagglutination test (MAT) and by standard tube agglutination test, respectively. Of subjects exposed to farm animals 73.4 % were positive for anti C. burnetii IgG (titer ≥ 20) compared to 13.6 % of control subjects (p<0.0001). The seroprevalence was found mainly among the veterinarians (100 %) and the animal breeding workers (84 %). The trend of percentage of positivity to antibodies to C. burnetii is significant only in the group of workers ≥70 years, when adjusted for sex and occupation. None of the subjects examined had antibodies to Leptospira and Brucella. Further improvements in the occupational hygiene of the work environment is advisable.