133 | Biodiversity and eco-epidemiological distribution of Rickettsia spp. in different biological matrices and vectors in Sicily

Santina Di Bella, Virginia Talarico, Cristina Panteghini, Francesca Gucciardi, Giuseppa Purpari, Antonina Princiotta, Valeria Blanda, Elisa Maria Petta, Valeria Vaglica, Annalisa Guercio | Istituto Zooprofilattico Sperimentale della Sicilia “A Mirri”, Palermo, Italy.

Rickettsia spp. are obligate intracellular bacteria primarily transmitted by hematophagous arthropods and represent a relevant biological model for investigating host–vector–pathogen interactions, as well as the mechanisms underlying microbial biodiversity and their implications for public and veterinary health. The Mediterranean area, and Sicily in particular, owing to its distinctive climatic, biogeographical, and ecological characteristics, provides a favorable setting for the persistence, diversification, and co-circulation of arthropod vectors and vector-borne pathogens (Vector-Borne Diseases, VBDs). The aim of this study was to characterize the biodiversity of Rickettsia spp. across different biological matrices and a wide range of arthropod vectors by adopting an integrated approach combining molecular biology techniques and eco-epidemiology. The study was conducted in several areas of Sicily and included blood samples from companion animals (dogs, cats, and horses), ticks and fleas collected from companion animals, livestock (cattle) and wildlife (foxes, wild boars, and fallow deer), free-living ticks collected from the environment, as well as hematophagous dipterans potentially involved in Rickettsia transmission cycles. All samples underwent nucleic acid extraction and were subsequently analyzed using molecular techniques for the detection of Rickettsia spp.. Molecular characterization was performed through the amplification and sequencing of conserved and discriminatory target genes, including gltA, ompA, and ompB. This approach enabled accurate species-level identification and allowed discrimination among Rickettsia species considered pathogenic, potentially pathogenic, or of low or uncertain pathogenicity. The analyses revealed a high degree of rickettsial heterogeneity, with the identification of multiple species, including Rickettsia conorii, R. conorii subsp. israelensis, R. africae, R. felis, R. asemboensis, R. massiliae, R. slovaca, R. aeschlimannii, R. monacensis, R. helvetica, and Candidatus Rickettsia barbariae, associated with different vectors, vertebrate hosts, and environmental compartments. The distribution of the detected species highlights the co-circulation of Rickettsia with varying pathogenic potential within the same ecosystems, suggesting the presence of complex and partially overlapping transmission cycles. In particular, the detection of zoonotic species in vectors associated with both domestic animals and wildlife underscores the critical role of ecological interfaces between natural environments, rural settings, and anthropized areas. Companion animals emerge as potential epidemiological sentinels and as possible links between sylvatic and peri-domestic transmission cycles of Rickettsia spp. Overall, the results confirm the high rickettsial biodiversity present in Sicily and reinforce the importance of adopting integrated and multidisciplinary approaches in the study of vector-borne diseases. This work contributes significantly to the understanding of the eco-epidemiological dynamics of Rickettsia spp. and supports the value of the integrated biodiversity concept within the One Health framework, highlighting the interconnectedness of animal health, human health, and the environment.

The research was funded by the Italian Ministry of Health: IZSSI 03/23 RC.