Cindy López Sánchez defended this Degree Final Project

July 3^rd, 2025

Q fever is an emerging zoonosis caused by the multi-host bacterium Coxiella burnetii, which has a worldwide distribution and affects numerous animal species. Spain is one of the countries that reports the most cases annually to the ECDC. Ruminants are the main source of infection for humans, although wildlife plays a significant role as a reservoir for this pathogen, particularly the European rabbit (Oryctolagus cuniculus), whose populations are increasing due to factors such as species traits, regional characteristics, and changes in interaction patterns between rabbits, domestic animals and humans. Previous studies in different areas of Spain have indicated the presence of C. burnetii in these species. However, the prevalence of this bacterium in rabbits from the Community of Madrid (CM) is unknown, and determining it was the aim of this study. A total of 99 rabbits were analyzed, collected from different areas of the CM in 2024, from which 99 spleen samples, 47 vaginal swabs, 10 fecal samples and 3 ticks were obtained for real-time PCR testing. Additionally, liver exudate from 99 samples was analyzed to detect anti-C. burnetii antibodies using an ELISA technique. The demonstrated seroprevalence was 2% (95% CI: 0.56%–7.07%) under a conservative approach and 7% (95% CI: 3.47%–13.8%) under a sensitive approach, obtaining a statistically significant association between the location of the animals (inside/outside the leishmaniasis outbreak) and seropositivity. However, no C. burnetii DNA was detected in any of the samples analyzed, suggesting an absence of active infection/ bacterial shedding in the sampled animals. Despite this, the detection of antibodies in several animals suggests that C. burnetii is currently circulating in the rabbit population of the CM, although with a lower prevalence than in other parts of Spain. This may be related to the fact that the CM is not an endemic area for Q fever, its lower proximity to domestic ruminants, the absence of disease outbreaks during the study period, vaccination measures in ruminants, and differences in the samples analyzed. However, these species could act as reservoirs and potential sources of infection for other species, including humans, thereby having a significant impact on public health. Therefore, it is essential to maintain surveillance of these populations, increasing the number and type of samples in future studies, and develop effective measures for the control and prevention of Q fever