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 calves tested at birth were seronegative, suggesting congenital transmission is not a significant route. Notably, 95% of seronegative newborn calves seroconverted within 24 hours of drinking an imported commercial colostrum replacer, indicating that such products may be a source of C. burnetii exposure and a potential confounder in seroepidemiological surveys of dairy herds.
UK applicability
These findings are relevant to UK dairy practice where colostrum replacers are commonly used. The identification of colostrum replacer as a potential source of C. burnetii exposure warrants consideration in UK herd health protocols and serological surveillance programmes, particularly given the zoonotic risk to farm workers and the requirement to manage Q fever in livestock.
Key measures
Anti-C. burnetii IgG serology (ELISA) in 266 serum samples from 133 cows and their calves; C. burnetii DNA detection (PCR) in 179 blood samples; seroconversion rates in calves following colostrum replacer ingestion
Outcomes reported
The study investigated C. burnetii seroprevalence and PCR positivity in a dairy herd experiencing abortion, and determined whether seronegative newborn calves seroconverted following ingestion of imported colostrum replacer. Findings suggest congenital transmission is not a significant route of infection in live-born calves, but commercial colostrum replacer may be a source of seroconversion.
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