Serological and Molecular Detection of Coxiella Burnetii in Clinical Samples from Veterinarians and Cattle Farm Workers from Gabrovo Region, Bulgaria

Coxiella burnetii, which causes Q fever, is a highly infectious agent that is widespread around the world.  During the last decades, the number of cases reported in Bulgaria varied from year to year. The present study aimed to determine the frequency of C. burnetii infection using ELISA and conventional PCR among freelance veterinarians and cattle farm workers in Gabrovo province, Bulgaria. In the period April 2020 to June, 2021 a total of 154 blood samples of target group was tested in the National Reference Laboratory of Cell cultures, rickettsia and oncogenic viruses (NRL CCROV) at NCIPD - Sofia. Diagnosis of C. burnetii was performed by indirect enzyme-linked immunosorbent assay ELISA (anti-Coxiella burnetii ph. II IgG/IgM) and by end-point PCR technique (to detect the sodB gene region of C. burnetii). By indirect ELISA assay of the tested 154 clinical samples, anti-C. burnetii positive ph. II IgM antibodies were registered in 37% of samples. A relatively high percentage are affected in the active age between 50-60 years old. Anti-C. burnetii positive ph. II IgG antibodies were proven at 50% of tested samples. A positive PCR signal for C. burnetii DNA was obtained at 37/154 (20% of samples) and follows the above reported trend of acute infection of active age patients. Around 10% of tested samples were positive for three C. burnetii laboratory markers. We conclude that Q fever is endemic in Bulgaria. More research is necessary in different Bulgarian regions to set the human risk groups, to diagnose acute and chronic Q fever and to determine the economic impact of Q fever in the cattle industry. In the NRL CCROV was developed diagnostic scheme including complex methods to improve early laboratory diagnosis of C. burnetii, allowing taking proper treatment of suspected with Q fever patients

Mini Review: Q Fever (Coxiellosis): Epidemiology, Pathogenesis and Current Laboratory Diagnosis

Q fever is zooantroponozis with global distribution caused by the strictly intracellular bacterium Coxiella burnetii. Causative agent of Q fever is an obligate intracellular parasite, classified in the genus Coxiella, family Coxiellaceae, class Gammaproteobacteria. The importance of the disease was assessed both in terms of human health and the serious economic damage they cause on livestock. Clinical manifestation of Q fever in humans is characterized by a wide variety - from asymptomatic infection to a chronic disease that can be fatal. Several basic methods have been developed to detection of C. burnetii. PCR and C. burnetii genomic sequences in whole blood are a sensitive and safe method of detection, with >90% sensitivity. A four-fold or greater rise of (CF) antibody (phase 2) between the paired sera is also diagnostic approach. Sensitivity of a four-fold rise in titre has been estimated as 73% ÷78% and specificity has been estimated as 90%, respectively. EIA is method with highly sensitive and specific. EIA detect IgM and then IgG antibodies which develop to phase II antigens in 10 to 14 days from symptom onset. IFA tests are of particular value for confirmation of acute infection and for diagnosis of chronic infection with high sensitivity. The technique detected IgG, IgM and IgA immunoglobulin classes. Suitable specimens for C. burnetii detection are blood samples. Although scientific interest in Q fever has always existed, a number of facts concerning the unforeseen nature of the epidemic, various clinical manifestations both in humans and in animals, the opportunities for chronic and other features of infection remain unclear. For this reason, timely and highly sensitive laboratory diagnosis is crucial for the outcome of the disease and subsequent treatment and monitoring