Population Structure and Evidence for Both Clonality and Recombination among Brazilian Strains of the Subgenus Leishmania ( Viannia)

Abstract

Background/Objectives: Parasites of the subgenus Leishmania (Viannia) cause varying clinical symptoms ranging from cutaneous leishmaniases (CL) with single or few lesions, disseminated CL (DL) with multiple lesions to disfiguring forms of mucocutaneous leishmaniasis (MCL). In this population genetics study, 37 strains of L. (V.) guyanensis, 63 of L. (V.) braziliensis, four of L. (V.) shawi, six of L. (V.) lainsoni, seven of L. (V.) naiffi, one each of L. (V.) utingensis and L. (V.) lindenbergi, and one L. (V.) lainsoni/ L. naiffi hybrid from different endemic foci in Brazil were examined for variation at 15 hyper-variable microsatellite markers.

Methodology/Principal findings: The multilocus microsatellite profiles obtained for the 120 strains were analysed using both model- and distance-based methods. Significant genetic diversity was observed for all L. (Viannia) strains studied. The two cluster analysis approaches identified two principal genetic groups or populations, one consisting of strains of L. (V.) guyanensis from the Amazon region and the other of strains of L. (V.) braziliensis isolated along the Atlantic coast of Brazil. A third group comprised a heterogeneous assembly of species, including other strains of L. braziliensis isolated from the north of Brazil, which were extremely polymorphic. The latter strains seemed to be more closely related to those of L. (V.) shawi, L. (V.) naiffi, and L. (V.) lainsoni, also isolated in northern Brazilian foci. The MLMT approach identified an epidemic clone consisting of 13 strains of L. braziliensis from Minas Gerais, but evidence for recombination was obtained for the populations of L. (V.) braziliensis from the Atlantic coast and for L. (V.) guyanensis.

Conclusions/Significance: Different levels of recombination versus clonality seem to occur within the subgenus L. ( Viannia). Though clearly departing from panmixia, sporadic, but long-term sustained recombination might explain the tremendous genetic diversity and limited population structure found for such L. ( Viannia) strains.

Author Summary

Cutaneous leishmaniasis (CL) constitutes a significant public health problem in all federal states of Brazil. Most cases are caused by parasites of the subgenus Leishmania (Viannia) which can cause a variety of clinical symptoms ranging from single or few lesions, disseminated CL with multiple lesions, to disfiguring forms of mucocutaneous leishmaniasis. This study has used a multilocus microsatellite typing approach for exploring the genetic diversity and population structure among 120 strains representing different subgenus L. (Viannia) species and different Brazilian CL foci. Genetic diversity within the subgenus was much higher than expected, especially within L. (V.) braziliensis, L. (V.) shawi, L. (V.) naiffi, and L. (V.) lainsoni which were all from the north of Brazil. These strains could not be assigned to well-defined populations, but presented a rather loosely associated group. Strains of L. (V.) braziliensis isolated along the Atlantic coast of Brazil and strains of L. (V.) guyanensis formed, however, two clearly separated populations exhibiting remarkable levels of sexual exchange. The latter finding is in contrast to previous studies suggesting clonal modes of propagation or inbreeding for natural populations of Leishmania parasites and might explain the genetic heterogeneity and limited population structure for Brazilian strains of subgenus L. ( Viannia) observed in this study.