Vectors and hosts other than dog in the epidemiology of Leishmania infantum

This doctoral thesis aims to provide original data on the epidemiology and transmission dynamics of this complex vector-borne disease in order to improve the current knowledge and the ongoing control strategies. The thesis is presented in form of “thesis by publication” and is composed by three chapters. Chapter 1 is divided into 2 sections. Survey included in Section 1.1 provide evidence-base data on the efficacy and safety of the concomitant use of two antiparasitic drugs, namely Frontline Tri-Act and NexGard Spectra in dogs for six months. This combination is now proposed as a comprehensive prevention strategy in dogs where the risk of leishmaniosis and other vector-borne zoonotic diseases overlaps. Additionally, in Section 1.2, a case of feline leishmaniosis with a long-term follow-up is described, with the aim to provide data on clinical manifestations, pathological abnormalities, diagnosis and treatment of this poorly documented disease of cat, and to emphasize the susceptibility of this animal species to Leishmania infection, advocating the adoption of effective preventive measures in cats that live in endemic areas. Chapter 2 is divided into 3 sections focused on phlebotomine sand flies as unique proven vectors able to transmit Leishmania infection. In Section 2.1, the attractiveness of light traps equipped with different colored LED to phlebotomine sand fly endemic in the Mediterranean basin is described. Light trap equipped with UV LED showed a higher attractiveness to P. perniciosus, representing an effective alternative technology in sand flies monitoring to be employed in entomological surveys. In Section 2.2, the employment of MALDI-TOF mass spectrometry as a novel method for rapid, simple and reliable phlebotomine sand fly species identification, compared to the conventional morphological method is described. MALDI-TOF produced distinct, consistent and reproducible specie-specific protein spectra of the sand fly species analyzed, with no differences between males and females. Gained results strongly support its advantageous use in entomological surveys as reliable and quicker approach to sand fly species identification, improving the knowledge on the spread of these vectors of medical importance. In Section 2.3, natural Leishmania infection and blood-feeding preferences were molecularly investigated in wild caught phlebotomine sand flies in Sicily along two transmission seasons in order to assess the risk of transmission of Leishmania spp., and to recognize potential reservoir hosts for leishmaniosis. The detection of L. infantum DNA in P. perniciosus confirms the role of this species in the maintenance and spread of leishmaniosis in Sicily. The blood-feeding preference of P. perniciosus to rabbit incites to better clarify the hypothesis on the involvement of this wild host in the epidemiology of leishmaniosis as sylvatic reservoir. Finally, the presence of L. infantum, L. tarentolae and Trypanosoma sp. DNA in S. minuta, together with the anthropophilic feeding-behaviour observed, spurs to clarify the ability of this species in the transmission of pathogens to humans and other warm-blooded animals. In Chapter 3, the circulation of Leishmania infantum in sylvatic mammals was molecularly and serologically investigated, providing first evidence of infection in Sicily. A low prevalence of infection was recorded, suggesting a minimal involvement of these animal populations in the epidemiology of leishmaniosis in Sicily. Nevertheless, the intrinsic constrains in diagnose Leishmania infection in wild animals do not definitively allow to exclude their involvement as alternative sylvatic hosts and future studies are needed to better define their role in the epidemiology of leishmaniosis in Sicily.