Detection of abortifacient agents in domestic ruminants, with a specific focus on Coxiella burnetii

Q fever is a widespread zoonotic disease caused by the bacterium, <i>Coxiella burnetii</i>. In ruminants, <i>C. burnetii</i> can cause abortions, stillbirths, premature births, and weak offspring. As part of the EU-funded Q-Net-Assess International Coordination of Research on Infectious Animal Diseases (ICRAD)-project, aimed at generating the most comprehensive understanding of <i>C. burnetii</i> genetic variation to date and determining the implications of this genetic variation for zoonotic risk, pathogenicity and control of <i>C. burnetii</i> infection, we have reviewed the protocols reported by the different project partners and/or countries to diagnose abortion in domestic ruminants. As a result of this review, we have developed guidelines for the detection of abortifacient agents in domestic ruminants, with a special focus on <i>C. burnetii</i>. They include a description of the essential and complementary samples needed for a definitive diagnosis, the analytical techniques to be used, and the interpretation and validity of each type of sample and technique. The most comprehensive diagnostic approach to identify an infectious agent as the cause of abortion in ruminants would include histopathology, including immunohistochemistry (IHC), on the fetus and placental membranes, complemented by bacteriology, serology, and real-time PCR analyses of different types of samples. For the specific diagnosis of <i>C. burnetii</i> as the causative agent of abortion, we provide guidelines based on expert opinions for the interpretation of laboratory test results in relation to their diagnostic value.