Abstract
Pathogen fitness landscapes change when transmission cycles establish in non-native environments or spill over into new vectors and hosts. The introduction of Leishmania infantum in the Americas into the Neotropics during European colonization represents a unique case study to investigate the mechanisms of ecological adaptation of this important parasite. Defining the evolutionary trajectories that drive L. infantum fitness in this new environment are of great public health importance as they will allow unique insight into pathways of host/pathogen co-evolution and their consequences for region-specific changes in disease manifestation. This review summarizes current knowledge on L. infantum genetic and phenotypic diversity in the Americas and its possible role in the unique epidemiology of visceral leishmaniasis (VL) in the New World. We highlight the importance of appreciating adaptive molecular mechanisms in L. infantum to understand the parasite’s successful establishment on the continent.
Highlights
Leishmania infantum, an etiological agent of visceral leishmaniasis (VL), is a member of the globally dispersed Leishmania donovani species complex, prevalent in many regions of the African, American, Asian, and European continents
We describe the underestimated diversity of the neotropical L. infantum parasite and its possible role in generating unique epidemiological patterns and clinical outcomes of VL
Parasite expansion into new environments and new host/vector populations creates potential for strong natural selection and bottlenecks, and associated genetic drift can provide the opportunity for rapid evolutionary change
Summary
Leishmania infantum, an etiological agent of visceral leishmaniasis (VL), is a member of the globally dispersed Leishmania donovani species complex, prevalent in many regions of the African, American, Asian, and European continents. Genetically similar L. infantum strains were described, causing dermal (CL) and visceral (VL) leishmaniasis in Honduras [29,30,31], in contrast to descriptions from the Old World. In the Mediterranean region, L. infantum parasites cause cutaneous and visceral disease [32,33,34,35] with significant correlations detected between zymodeme and pathology, as well as genetic differentiation between viscerotropic and dermotropic zymodemes by random amplified polymorphic DNA (RAPD)–PCR fingerprinting [36,37]. Multilocus microsatellite typing (MLMT) by Ferreira et al [38] detected substantial population structure in the New World, distinguishing three divergent L. infantum populations within Brazil Such findings call for the application of more resolutive, generation sequencing (NGS)-based studies to better understand. New World L. infantum diversity, including genomic structural variation, which is considered a major driver of adaptation in the Leishmania genus, as detailed
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