Sand Fly Fauna and Prevalence of Leishmania spp. in a Newly Investigated Area of Northern Italy: Emerging Epidemiological Scenarios?

Since the 1990s, cases of canine leishmaniasis (CanL) due to Leishmania infantum have risen in northern Italy due to dog translocation and movement as well as for climate-driven sand fly population growth. In this geographical region, for a long time regarded as non-endemic for CanL, L. infantum is generally transmitted by the sand flies of the genus Phlebotomus. Other sand flies, such as Sergentomyia minuta, have been less investigated, also because they were only considered as vectors of the nonpathogenic herpetophilic Leishmania tarentolae. Our study investigates sand fly species composition and Leishmania spp. prevalence in hilly areas of northern Italy, in the Bergamo district. Sand flies were sampled with both sticky and light traps. Common wall lizards Podarcis muralis have been captured in the same areas, for the collection of biological samples: blood, feces, tissues, and gut-associated secretions. Sand flies were identified morphologically (males) and molecularly (females). The collected samples were tested for the presence of Leishmania spp. via conventional and digital droplet PCR. Our study reports the presence of Phlebotomus perniciosus, Phlebotomus neglectus, and S. minuta in the investigated area. We report the first detection of L. tarentolae, a Sauroleishmania species, in northern Italy, in both sand fly vectors (S. minuta, P. perniciosus, and P. neglectus) and reptile hosts. Additionally, L. infantum DNA was detected, for the first time, in sand flies and reptiles in the district, spatially overlapping with previously reported local CanL cases. Our study reported the presence of three sand fly species in the Bergamo district, a Sauroleishmania species (the first record in northern Italy), and the occurrence of L. infantum. We emphasize the importance of including both S. minuta sand flies and synanthropic reptiles in leishmaniasis screenings for a better understanding of the epidemiology of the disease.