[The effect of herd and animal factors on the detection of complement-binding antibodies against Coxiella burnetii in cattle].

To determine the prevalence of bovine Coxiella (C.) burnetii infections in Northern Lower Saxony, blood serum obtained from a total of 2160 cattle was examined for antibodies against C. burnetii using the complement fixation test (CFT). From 500 randomly sampled cattle, 38 (7.6%) were seropositive. In 383 cows out of 33 dairy herds with the history of reproductive problems a significantly higher prevalence of C. burnetii specific antibodies was found than in 665 cows out of 39 herds without reproductive problems (19.3% vs. 9.6%). In both groups, mean CFT titer increased significantly with the degree of the within herd prevalence. Furthermore, in dairy herds with fertility problems the within herd prevalence was significantly higher than in dairy herds not experiencing infertility (24.3% vs. 11.2%). A relationship between serological evidence of C. burnetii infection and incidence of reproductive disorders observed in lowered fertility herds was not found. Statistical analysis of CFT results of 668 cows allocated in groups according to month of gestation, month prior insemination, and month postpartum revealed that the percentage of seropositives as well as CFT titers rise significantly in the 1st month of gestation and after a sharp decline in the 4th month increase a second time in the 7th month of gestation. Sera from 612 bulls aged six months to ten years yielded 5.2% seropositives. The most positives (87.5%) were found in bulls aged up to two and a half year. After a six month period, 428 bulls were retested. Specific antibodies were found in eight (27.6%) of 29 formerly seropositives. Seroconversion was not detected in any of 399 formerly seronegative bulls.