Relationship between abortions and seroprevalences to selected infectious agents in dairy cows.

The aim of this study was to determine whether the occurrence of abortion is related to the seroprevalence of abortion-causing infectious agents. In a cross-sectional study, cattle from dairy farms in Switzerland that were defined as having an abortion problem were divided into two groups: cows with a history of abortion within the previous 3 months (cases) and cows without a history of abortion (controls). A positive titre to Leptospira spp. was associated with an increased probability of being a case (OR = 1.74, 95% CI = 1.21-2.47). There were interactions between Coxiella burnetti titre and parity, and between Chlamydia psittaci and C. burnetti titre and breed. Multiparous cases after the second lactation with a positive titre to C. burnetti were less likely (OR = 0.42, 95% CI = 0.22-0.82) to be cases. Swiss Browns (Swiss Braunvieh and Brown Swiss) with a positive titre to C. psittaci and Swiss Browns with a positive titre to C. burnetti were more likely (OR = 1.63, 95% CI = 1.13-2.37 and OR = 1.79, 95% CI = 1.15-2.78, respectively) to be cases. Parity alone was not associated with the occurrence of abortion.