Abstract
A prevalence study was conducted on German sheep flocks including goats if they cohabitated with sheep. In addition, a novel approach was applied to identify an infection at the herd-level before lambing season with preputial swabs, suspecting venereal transmission and ensuing colonisation of preputial mucosa with Coxiella (C.) burnetii. Blood samples and genital swabs were collected from breeding males and females after the mating season and were analysed by enzyme-linked immunosorbent assay (ELISA) and quantitative polymerase chain reaction (qPCR) respectively. In total, 3367 animals were sampled across 71 flocks. The true herd-level prevalence adjusted for misclassification probabilities of the applied diagnostic tests using the Rogan-Gladen estimator for the prevalence estimate and a formula by Lang and Reiczigel (2014) for the confidence limits, ranged between 31.3% and 33% (95% confidence interval [95% CI] 17.3-45.5) detected by the ELISA and/or qPCR. Overall 26-36.6% (95% CI 13-56.8) were detected by ELISA, 13.9% (95% CI 4.5-23.2) by the qPCR and 7.9-11.2% (95% CI 0.08-22.3) by both tests simultaneously. The range of results is due to data obtained from literature with different specifications for test quality for ELISA. Among eight farms with females shedding C. burnetii, three farms (37.5%) could also be identified by preputial swabs from breeding sires. This indicates less reliability of preputial swabs if used as a single diagnostic tool to detect C. burnetii infection at the herd-level.
Highlights
Q fever is a zoonotic disease caused by the intracellular bacterium Coxiella burnetii
Occurrence of C. burnetii in German sheep flocks In this study, the occurrence of C. burnetii was determined in 71 farms located in five federal states of Germany
The results obtained depended on the selection of the farms/animals and the test systems used (ELISA and quantitative polymerase chain reaction (qPCR))
Summary
Q fever is a zoonotic disease caused by the intracellular bacterium Coxiella burnetii. Other animals like cats and dogs can be responsible for human Q fever infections [2, 3]. In animals and humans alike, the main infection pathway is the inhalation of pathogen-contaminated aerosols [5]. Aside from airborne dissemination of C. burnetii, sexual transmission has occasionally been reported in humans [6]. Different pathogens like Chlamydia spp. and Brucella spp. were detected in samples taken from the preputial mucosa in rams [9, 10]. This sampling method has rarely been used to diagnose C. burnetii infection in small ruminants [11]
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