A Retrospective Study of Genetic Characterization in Suspected Visceral Leishmaniasis Cases in Greece, 2005 to 2020.

Leishmania infantum is considered the predominant Leishmania species responsible for visceral leishmaniasis (VL) in Greece but limited molecular-typing-based studies have been performed so far. We retrospectively analyzed data and serum samples collected from 3661 individuals suspected for VL in a sixteen-year period, from 2005 to 2020, to study the seasonality and demographic characteristics of VL cases and to define the L. infantum genotypes circulating in the country. Serum samples were tested with immunofluorescence assay and/or molecular assay. qPCR Leishmania -positive samples were subjected to genotypic analysis based on polymorphisms in 12 microsatellite regions of the internal transcribed spacers (ITSs) 1 and 2. We diagnosed 219 definite (6%, sample with a positive molecular assay and/or antibody titer ≥ 1:400) and 230 probable (6.3%, sample with antibody titer between 1:100 and 1:200) VL cases. Data analysis revealed that amongst VL-definite cases, the age group (≥65) constitutes the most affected factor, since 36.9% of the VL cases belonged to this age group. Amongst the VL definite cases, the most frequently reported symptoms were fever (83%), splenomegaly (49%), and hepatomegaly (40%), but this was not the case for immunocompromised patients that developed non-typical symptoms of leishmaniasis. Although no statistically significant differences in the overall seasonality of VL cases were observed, February and June showed a significantly higher proportion of VL cases compared to August and December. Genotyping of ITS1 and ITS2 regions revealed that all VL cases belong to ITS type A of L. infantum. Our study provides epidemiological information on VL and demonstrates for the first time, providing genotypic data, the circulation of ITS type A L. infantum in Greece.