Molecular Survey of Zoonotic Rickettsia spp. in Wildlife, Companion Animals and Arthropod Vectors in Sicily: A One Health Approach

Rickettsia spp. are arthropod-borne intracellular bacteria of growing concern for animal and human health. Sicily (southern Italy), owing to its climate, biodiversity, and strategic location in the Mediterranean basin, provides favorable conditions for vector circulation and pathogen maintenance. This study investigated the occurrence and diversity of Rickettsia spp. across multiple hosts and vectors.

Between 2024 and 2025, a molecular survey was conducted across Sicily. A total of 3,203 samples were collected throughout all seasons and included blood from companion animals, ticks from companion animals, wildlife and vegetation, fleas from dogs, cats and foxes, and hematophagous dipterans. Following nucleic acid extraction, samples were screened for Rickettsia spp. by PCR targeting the gltA, ompA and ompB genes. Selected amplicons were further characterized by sequencing for species identification.

Overall, 279/3,203 samples (8.7%) tested positive for Rickettsia spp. The highest positivity rates were observed in fleas from dogs and cats (39.6%, 38/96) and dog-associated ticks (33%, 177/536), followed by free-living ticks (19%, 26/137), ticks from cats (18.2%, 2/11), and fallow deer ticks (5.2%, 13/248); one positive sample was detected among ticks collected from wild boars. Lower prevalences were found in feline blood (3.6%), hematophagous dipterans (2%), and canine blood (0.4%), whereas equine blood, horse ticks and fox fleas tested negative. Molecular characterization identified R. conorii, R. africae, R. felis, R. asemboensis, R. massiliae, R. slovaca, R. aeschlimannii, R. monacensis, R. helvetica, Candidatus R. barbariae, Candidatus R. yungkouensis and Candidatus R. shennongii. Pathogenic species were detected in vectors associated with both domestic animals and wildlife, suggesting complex transmission networks and potential zoonotic exposure.

The remarkable diversity of Rickettsia spp. circulating in Sicily highlights the complexity of transmission cycles linking wildlife, vectors and peri-domestic environments. Continuous multi-host and multi-vector surveillance within a One Health framework is essential to improve risk assessment and strengthen preparedness against emerging tick-borne zoonoses in the Mediterranean region.

Funding: Italian Ministry of Health – Projects IZSSI03/23RC and GR-2021-12373930