Leishmania infantum infection in Phlebotomus perniciosus and Phlebotomus perfiliewi (Diptera, Psychodidae) and their abundance in central Italy

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Abstract Background Leishmaniasis caused by the parasitic protozoan Leishmania infantum is endemic in central and southern Italy, but systematic vector surveillance has historically been lacking. Following human cases of visceral leishmaniasis reported in the Lazio and Tuscany regions of Italy, we implemented a surveillance system aimed at describing the occurrence, seasonal dynamics and infection rates of the main vector species in these regions, consequently identifying periods and areas at higher risk of transmission. Methods Sand flies were collected with CDC-CO 2 light traps from April to November 2023 at 75 rural and suburban farms and at three additional sites close to reported human leishmaniasis cases in urban areas. Traps were operated overnight at 1- or 2-week intervals, and the collected sand flies were sorted, counted and identified morphologically. Sites where sand flies were detected were characterised using bioclimatic variables and altitude, and then grouped into climate clusters using k -means clustering. Seasonal activity was analysed by fitting Gaussian generalised linear models with a negative binomial distribution to the abundance data. Pools of female sand flies were tested for L. infantum by real-time PCR, and infection rates were estimated per site and sampling date. Results A total of approximately 96,333 sand flies were captured in 40 of the 78 collection sites. Of the 13 provinces monitored, nine were positive for sand flies. Two species of sand flies were identified: Phlebotomus perfiliewi (76% of identified specimens) and P. perniciosus (24%), which co-occurred in most provinces. Three distinct climate clusters were defined, mainly separating coastal low-altitude areas from more inland, hilly sectors. Across clusters, adult sand fly activity peaked in early August, with longer activity periods and higher predicted abundances in coastal and low-altitude areas dominated by P. perfiliewi . Leishmania infantum DNA was detected in sand fly pools from eight sites in six provinces, with infected sand flies present from late June to mid-October. The highest infection estimates occurred at high-abundance rural foci dominated by P. perfiliewi and at hilly sites where P. perniciosus was more abundant. Conclusions Both P. perniciosus and P. perfiliewi contribute significantly to L. infantum circulation in central Italy. The areas at risk, seasonal vector dynamics and infection rates identified in this study provide essential information for the timing and targeting of veterinary and public health interventions and awareness campaigns.

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