Summary
Following a cluster of Q fever-related abortions in a Uruguayan dairy herd, this investigation traced the epidemiology of Coxiella burnetii infection in 133 calving cows and their calves. Whilst 22.5% of non-aborting cows were seropositive at parturition, congenital infection proved negligible; however, 95% of seronegative neonatal calves seroconverted within 24 hours of consuming an imported commercial colostrum replacer, suggesting this product as a contamination source and a potential confounder in seroepidemiological surveys.
UK applicability
This finding is directly relevant to UK dairy practice, as colostrum replacers are commonly used in both conventional and organic systems. The results indicate that serological surveys of C. burnetii in UK dairy herds must account for colostrum replacer use as a source of apparent seroconversion, potentially affecting disease prevalence estimates and herd-level risk assessments.
Key measures
Anti-C. burnetii IgG seroprevalence by ELISA in cows and calves; C. burnetii DNA detection by PCR; proportion of seronegative newborn calves seroconverting after colostrum replacer ingestion (95%)
Outcomes reported
The study documented seroprevalence of C. burnetii in a dairy herd following abortion cases, traced transmission routes in live-born calves, and demonstrated unexpected seroconversion in neonatal calves after ingestion of imported colostrum replacer. Serological and PCR testing established that vertical transmission was not the primary route of infection to live-born calves in this herd.
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