Molecular detection of Coxiella Burnetii in ovine abortions: evidence from a three-year surveillance in an endemic region

<i>Coxiella burnetii</i>, an obligate intracellular coccobacillus, is a major cause of abortion in livestock and a re-emerging zoonotic pathogen responsible for Q fever in humans. Iran, particularly Khorasan-e-Razavi Province, is considered endemic for Q fever. Rapid and accurate detection of <i>C. burnetii</i> in animal shedders, especially asymptomatic ones, is essential to control its spread among animals and from animals to humans. This study provides the first multi-year (2020-2022) quantitative assessment of <i>C. burnetii</i> infection load in ovine abortions in this endemic region. The objectives were to: (i) develop and validate a region-specific real-time PCR assay targeting the IS1111a gene through sequencing of the amplified fragment; (ii) quantify pathogen load using a standard curve derived from a sequenced reference fragment; and (iii) evaluate associations between prevalence and factors such as year, season, geographic location, and confirmed co-infections with other abortifacient agents. Liver samples from 116 aborted sheep fetuses were examined by real-time PCR, revealing a <i>C. burnetii</i> prevalence of 53.4%, while in 54.8% of these positive cases, <i>C. burnetii</i> was identified as the sole infectious pathogen contributing to abortion. A significant association (p < 0.05) between sampling year and prevalence was observed, with a rising trend over time. The high prevalence of <i>C. burnetii</i> and its role in abortion cases underscore the need for enhanced surveillance and control programs to mitigate the spread and impact of this pathogen in endemic regions.