Abstract
BackgroundThe dynamic re-emergence of visceral leishmaniasis (VL) in south Europe and the northward shift to Leishmania-free European countries are well-documented. However, the epidemiology of VL due to Leishmania infantum in southeastern (SE) Europe and the Balkans is inadequately examined. Herein, we aim to re-evaluate and compare the population structure of L. infantum in SE and southwestern (SW) Europe.MethodsLeishmania strains collected from humans and canines in Turkey, Cyprus, Bulgaria, Greece, Albania and Croatia, were characterized by the K26-PCR assay and multilocus enzyme electrophoresis (MLEE). Genetic diversity was assessed by multilocus microsatellite typing (MLMT) and MLM Types were analyzed by model- and distance- based algorithms to infer the population structure of 128 L. infantum strains.ResultsL. infantum MON-1 was found predominant in SE Europe, whilst 16.8% of strains were MON-98. Distinct genetic populations revealed clear differentiation between SE and SW European strains. Interestingly, Cypriot canine isolates were genetically isolated and formed a monophyletic group, suggesting the constitution of a clonal MON-1 population circulating among dogs. In contrast, two highly heterogeneous populations enclosed all MON-1 and MON-98 strains from the other SE European countries. Structure sub-clustering, phylogenetic and Splitstree analysis also revealed two distinct Croatian subpopulations. A mosaic of evolutionary effects resulted in consecutive sub-structuring, which indicated substantial differentiation and gene flow among strains of both zymodemes.ConclusionsThis is the first population genetic study of L. infantum in SE Europe and the Balkans. Our findings demonstrate the differentiation between SE and SW European strains; revealing the partition of Croatian strains between these populations and the genetic isolation of Cypriot strains. This mirrors the geographic position of Croatia located in central Europe and the natural isolation of the island of Cyprus. We have analysed the largest number of MON-98 strains so far. Our results indicate extensive gene flow, recombination and no differentiation between MON-1 and MON-98 zymodemes. No correlation either to host specificity or place and year of strain isolation was identified. Our findings may be associated with intensive host migration and common eco-epidemiological characteristics in these countries and give valuable insight into the dynamics of VL.
Highlights
The dynamic re-emergence of visceral leishmaniasis (VL) in south Europe and the northward shift to Leishmania-free European countries are well-documented
Our sample-set comprises 101 MON-1 strains, 21 MON-98 strains from Turkey and Greece, and 6 Turkish L. infantum strains of unknown zymodeme type
The presence of L. infantum sand fly vectors and stable parasite circulation in Stara Zagora [49] highlights the necessity to conduct a comprehensive entomological and epizootic survey for the identification of Leishmania vectors and the isolation of Leishmania parasites from sand flies, human and canine hosts. This would give the opportunity to thoroughly investigate the population structure of L. infantum spp. and disease dynamics in Bulgaria. This is the first study that gives an insight into the population structure of L. infantum in Cyprus located at the SE edge of Europe and the Balkans (Turkey, Bulgaria, Greece, Albania and Croatia)
Summary
The dynamic re-emergence of visceral leishmaniasis (VL) in south Europe and the northward shift to Leishmania-free European countries are well-documented. Based on multilocus enzyme electrophoresis (MLEE), the current reference method for characterizing and classifying Leishmania strains [6], L. infantum MON-1 is the predominant zymodeme in all Mediterranean countries [7,8,9], while the genetically close L. infantum zymodeme MON-98 has occasionally been reported in Turkey [10], Cyprus [11], Egypt [12,13], Greece [5,14,15] and Portugal [16]. Feline leishmaniasis is reported in countries highly endemic for CanL [19] and cats were recently found capable of transmitting MON-1 parasites to a proven L. infantum vector, Phlebotomus perniciosus [17]. Clinically affected dogs are more prone to infect sand fly vectors, those being sub-clinically infected and seronegative can transmit Leishmania parasites to sand flies and, contribute to the parasites’ maintenance [20,21,22,23,24]
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