Integrated One Health surveillance of human, canine and sand fly Leishmania infantum transmission in Sicily, southern Italy

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BACKGROUND: Leishmaniasis is an endemic vector-borne disease in Sicily, sustained by Leishmania infantum, with dogs acting as the primary reservoir and phlebotomine sand flies as the main vectors. Climatic changes may influence transmission dynamics, but integrated epidemiological data remain limited in several high-risk areas of the island. METHODS: A One Health surveillance study was conducted between 2022 and 2024 in three Sicilian provinces (Palermo, Agrigento, and Caltanissetta). Human cases were identified through active hospital-based surveillance, and socio-demographic risk factors were assessed using structured questionnaires. Canine infection was evaluated through immunofluorescence antibody test-based serosurveys in owned and shelter dogs. Entomological monitoring was performed using CDC light traps in peri-domestic environments. Climatic variables (temperature and precipitation) were analyzed in parallel with vector captures. RESULTS: A total of 67 confirmed human leishmaniasis cases were detected (50 cutaneous and 17 visceral), with a higher proportion of cases among outdoor workers and smokers. Canine seroprevalence ranged from 12 to 34% and spatially overlapped with human case-detection patterns. Entomological collections yielded 75,376 sand flies, with Caltanissetta accounting for 80.6% of specimens. Phlebotomus perniciosus was the predominant species, while Ph. papatasi was detected in Agrigento. Higher sand fly capture counts were observed during warm months (20-28 °C) following periods of moderate rainfall. Increasing temperature and precipitation trends coincided with the highest levels of relative sand fly activity observed in 2024. CONCLUSIONS: These findings confirm ongoing L. infantum transmission in Sicily and demonstrate the ecological alignment between human cases, canine reservoirs, vector captures, and climatic conditions. Climatic trends may contribute to an extension of the seasonal transmission window. Integrated veterinary and entomological surveillance can provide early signals of transmission intensification and support targeted interventions in high-risk endemic areas.

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