An assessment of the genetic diversity of Leishmania infantum isolates from infected dogs in Brazil

Abstract

Correlations between the genetic diversity of Leishmania infantum (syn. L. chagasi) isolates and their respective geographic origins support the theoretic assumption that visceral leishmaniasis probably originated in the Old World. Because dogs are widely considered to be the main reservoir of this disease, the present study aimed to investigate the degree of genetic divergence among 44 leishmanial canine isolates from two Brazilian cities, Jequié and Campo Grande, located approximately 2,028 km from each other. We hypothesized that a low degree of genetic divergence would be observed among these isolates. In fact, statistical analyses found no significant differences between the isolates using both random amplified polymorphic DNA and multilocus microsatellite typing genotyping techniques with three and seven markers, respectively. These findings provide support for the recent introduction of L. infantum into the New World.

Figure 1.

Genotypic profiles generated from RAPD reactions (primer B-01) using Jequié and Campo Grande isolates. Reaction products were separated by electrophoresis in an agarose gel; images were captured under ultraviolet light. The Lb13500 strain of L. braziliensis (Lb) and La483 strain of L. amazonensis (La) were used as outgroups, and the MHOM/BR/00/MER02 strain was used as a reference for L. infantum (Li) species. Arrows indicate polymorphic bands. CG = Campo Grande isolate; J = Jequié isolate; MW = molecular weight.

Figure 2.

Neighbor-joining dendrogram generated from RAPD profiles illustrates the genetic distances between the L. infantum isolates. The bootstrap value is indicated in bold. A = cluster containing isolates only from Campo Grande; B = cluster containing isolates only from Jequié; bar size = genetic distance among isolates; CG = Campo Grande isolate; J = Jequié isolate.

Figure 3.

The neighbor-joining dendrogram built from MLMT profiles illustrating the genetic distances between the L. infantum isolates. MER02 is the L. infantum reference strain (MHOM/BR/00/MER02). A = cluster containing isolates only from Campo Grande; B = cluster containing isolates only from Jequié; C = cluster containing isolates from Campo Grande and Jequié; CG, isolates from Campo Grande; J, isolates from Jequié. The bars at the right show the estimated population structure as inferred by STRUCTURE.