Q Fever: Who Is at Risk? A Serological Survey in the General Population and Occupationally Exposed Individuals in Northern Italy

Background: Q fever is a zoonotic disease caused by the intracellular bacterium Coxiella (C.) burnetii. In ruminants, it mainly leads to reproductive disorders. In humans, transmission typically occurs through direct contact with infected animals or inhalation of contaminated aerosols. Although it is a notifiable disease in the European Union for both humans and certain animal species, the actual incidence is likely underestimated due to the non-specific nature of clinical symptoms. Domestic ruminants are considered the main reservoirs of C. burnetii, placing farmers and veterinarians at increased occupational risk of infection. Objectives: This study aimed to assess the risk of Q fever infection in northern Italy by comparing the seroprevalence rates between professionally exposed individuals and not professionally exposed people. Methods: A total of 209 serum samples were analysed: 117 from exposed professionals (veterinarians, biologists, agronomists, laboratory technicians) and 92 from professionally unexposed people (control group). Serum samples were tested with a commercial enzyme-linked immunosorbent assay to detect the presence of IgG against C. burnetii. Positive and doubtful samples were further investigated with a commercial immunofluorescence assay for detection of IgM and IgG. Epidemiological data were also collected to explore potential risk factors. Results: In total, 10 of the 117 exposed individuals tested positive, yielding a seroprevalence of 8.6%, while only 1 of the 92 control subjects tested positive (1.1%). These findings indicate a significantly higher occupational risk of C. burnetii infection among exposed professionals compared to the general population. Conclusions: The results highlight the need for preventive measures and surveillance in at-risk occupational groups.