Coxiella burnetii seropositivity is highly stable throughout gestation in lactating high-producing dairy cows.

The aims of this study were to analyse, in high-producing dairy cows, plasma Coxiella burnetii antibody titres and seroconversion throughout gestation, along with possible factors affecting such titres. The study was performed on 65 lactating pregnant non-aborting animals in a commercial Holstein-Friesian dairy herd in northeastern Spain. Blood samples for antibody determinations were collected on days 40, 90, 120, 150, 180 and 210 of gestation. By General Linear Model (GLM) repeated measures analysis of variance, the effects of milk production and reproductive variables as well as Neospora caninum-seropositivity on C. burnetii antibody levels for all animals and for seropositive animals were established. Significant effects were observed of day of gestation, parity and N. caninum-seropositivity (between subject effects) on the C. burnetii antibody levels recorded for the whole population of animals throughout the gestation period. C. burnetii antibody levels were higher in primiparous than in multiparous cows, with titres in primiparous cows diminishing during the post-partum period. In seropositive cows, significant effects were observed of milk production and inseminating bull on gestational C. burnetii antibody levels. When the data were subjected to binary logistic regression considering C. burnetii-seropositivity as the dependent variable, the resultant odds ratios indicated that the likelihood of C. burnetii-seropositivity was lower in N. caninum-seropositive animals (OR 0.12) compared to N. caninum-seronegative animals, and in multiparous cows (OR 0.12) compared to primiparous cows. In conclusion, Coxiella-infected dams remained seropositive during the whole gestation period, though primiparous cows showed a drop in antibody titres post-partum. No seronegative cow suffered seroconversion. Presence of both, N. caninum and C. burnetii antibodies in the same animal, was associated with a decrease in antibody titres against C. burnetii, perhaps indicating some cross-protection in animals infected by both pathogens.