Summary
This investigation of a C. burnetii abortion cluster in a Uruguayan dairy herd found that whilst 22.5% of cows were seropositive at parturition, all live-born calves tested negative at birth, suggesting congenital transmission is not a major infection route in this population. Notably, 95% of seronegative calves became seropositive within 24 hours of ingesting imported commercial colostrum replacer, a finding with important implications for seroepidemiological surveys in herds using such products.
UK applicability
The findings are relevant to UK dairy operations that rely on commercial colostrum replacers, particularly regarding the interpretation of Q fever serology in neonatal calves and the potential for passive transfer of maternal antibodies via colostrum replacer to confound disease surveillance. However, the applicability depends on whether similar colostrum replacer products are used in UK herds and whether C. burnetii exposure patterns are comparable.
Key measures
Serum anti-C. burnetii IgG by ELISA; C. burnetii DNA detection by PCR; seroprevalence rates; timing of seroconversion post-colostrum ingestion
Outcomes reported
The study measured C. burnetii seroprevalence in dairy cows and their calves, and investigated seroconversion in newborn calves after colostrum replacer ingestion. Findings indicated that vertical transmission was not a significant route of infection, but commercial colostrum replacer was associated with high rates of seroconversion.
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