[Follow-up studies of the detection of IgG1 antibodies to Coxiella burnetii in blood and milk from cattle in relation to the reproductive cycle and milk production].

During a 14 month period, 36 dairy cattle were selected from a herd (n = 103), after IgG1 antibodies to Coxiella burnetii had repeatedly been detected in blood and milk, as measured by ELISA. ELISA results were analyzed with reference to reproductive cycle, daily milk yield, as well as daily concentration, and output of milk protein. The rate of positive blood samples slightly grew from 47.6% in the non-pregnant period, and 46.8% in the first half of pregnancy to 52.0% in the second half of pregnancy. In contrast, results of milk ELISA changed significantly from non-pregnant period to first, and second half of pregnancy, with increases from 23.8 to 38.5, and 64.6% of positive milk samples. Moreover, milk samples showed negative correlations between ELISA OD405 values and daily milk yield, as well as daily output of milk protein.