The Genetic Structure of Leishmania infantum Populations in Brazil and Its Possible Association with the Transmission Cycle of Visceral Leishmaniasis

Abstract

Leishmania infantum is the etiologic agent of visceral leishmaniasis (VL) in the Americas, Mediterranean basin and West and Central Asia. Although the geographic structure of L. infantum populations from the Old World have been described, few studies have addressed the population structure of this parasite in the Neotropical region. We employed 14 microsatellites to analyze the population structure of the L. infantum strains isolated from humans and dogs from most of the Brazilian states endemic for VL and from Paraguay. The results indicate a low genetic diversity, high inbreeding estimates and a depletion of heterozygotes, which together indicate a predominantly clonal breeding system, but signs of sexual events are also present. Three populations were identified from the clustering analysis, and they were well supported by F statistics inferences and partially corroborated by distance-based. POP1 (111 strains) was observed in all but one endemic area. POP2 (31 strains) is also well-dispersed, but it was the predominant population in Mato Grosso (MT). POP3 (31 strains) was less dispersed, and it was observed primarily in Mato Grosso do Sul (MS). Strains originated from an outbreak of canine VL in Southern Brazil were grouped in POP1 with those from Paraguay, which corroborates the hypothesis of dispersal from Northeastern Argentina and Paraguay. The distribution of VL in MS seems to follow the west-east construction of the Bolivia-Brazil pipeline from Corumbá municipality. This may have resulted in a strong association of POP3 and Lutzomyia cruzi, which is the main VL vector in Corumbá, and a dispersion of this population in this region that was shaped by human interference. This vector also occurs in MT and may influence the structure of POP2. This paper presents significant advances in the understanding of the population structure of L. infantum in Brazil and its association with eco-epidemiological aspects of VL.

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

“…In conclusion, the only correlation found for MLMT patterns of the L. (Viannia) strains studied herein was that to their geographical origin. Similar observations were published earlier for L. (V.) braziliensis [11] and L. (L.) infantum in Brazil [53] and might be associated with different transmission cycles with different sand fly vectors and/or animal reservoirs involved in those areas.…”

Trans-Atlantic Spill Over: Deconstructing the Ecological Adaptation of Leishmania Infantum in the Americas

“…In contrast, a more recent study with representative sampling from different Brazilian regions analyzed by Random Amplified Polymorphic DNA (RAPD) showed that despite the relative genetic homogeneity, most isolates clustered according to geographical origin [28]. Likewise, 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, Next Generation Sequencing (NGS)-based studies to better understand New World L. infantum diversity, including genomic structural variation, which are considered a major driver of adaptation in the Leishmania genus as detailed in the following section.…”

“…most of the Brazilian states endemic for VL and from Paraguay [38]. Samples grouped in three genetically distinct populations: POP1 (relatively more frequent) was observed in all but one endemic area; POP2 was also well-dispersed, but predominant in Mato Grosso (MT), characterized by the presence of distinct biomes harboring intense biodiversity (Amazon, Cerrado and Pantanal); POP3 was less dispersed and observed primarily in Mato Grosso do Sul (MS), likely composed by variable biomes (Cerrado, Atlantic forest and Pantanal).…”

Genetic Structure of Lutzomyia longipalpis Populations in Mato Grosso Do Sul, Brazil, Based on Microsatellite Markers

“…Visceral leishmaniasis is an anthropozoonosis characterized by chronic evolution and systemic involvement, which if untreated can result in death. In the Americas, Leishmania (L.) infantum is the etiological agent of the disease and Brazil accounts for over 90% of the cases on the continent [3-6]. …”