Descriptive statistics and data analysis
Of the 350 bovine serum samples that were tested by ELISA, 41.4% (145/350) were seropositive for C. burnetii, 0.0% (0/350) forB. abortus, 1.7% (6/350) for L. Hardjo , 1.4% (5/350) forN. caninum , and 0.3% (1/350) for BVDV (Table 1; Figure 1). By comparison 58.6% (205/350) were seronegative for C. burnetii , 100.0% (350/350) were seronegative for B. abortus , 98.3% (344/350) seronegative to L. Hardjo , 98.6% (345/350) negative toN. caninum , and 99.7% (349/350) were negative for BVDV antigen (Table 1; Figure 1). Furthermore, of the dairy cattle that were screened by ELISA in the present study, 30.0% (105/350) had history of abortion while 70.0% (245/350) did not have any history of abortion. Interestingly, of the 105 cattle that had history of abortion, 61.9% (65/105) were seropositive for C. burnetii , 2.9% (3/105) forL. Hardjo , 1.0% (1/105) for N. caninum, 0.0% (0/105) for BVDV, and 0.0% (0/105) for B. abortus . When the number of seropositive cattle without history of abortion are considered, 32.7% (80/245) were positive for antibodies against C. burnetii , 0.0% (0/245) for B. abortus , 1.2% (3/245) for L. Hardjo , 1.6% (4/245) for N. caninum , while 0.0% (0/245) were negative for BVDV antigen (Table 2; Figure 2). It is noteworthy that of the 105 cattle that had a history of abortion, 61.9% (65/105) were seropositive for C. burnetii . By comparison, of the 245 cattle that did not have a history of abortion, 32.7% (80/245) were seropositive forC. burnetii . The z-test shows that the proportion of C. burnetii seropositive cattle with a history of abortion was significantly higher than the C. burnetii seropositive cattle that did not have a history of abortion [p-value < 0.01] with the difference between the proportions of 29.3% [95% CI: 18.2% to 40.2%].