Abstract
BackgroundParasites' evolution in response to parasite-targeted control strategies, such as vaccines and drugs, is known to be influenced by their population genetic structure. The aim of this study was to describe the population structure of Ethiopian strains of Leishmania donovani derived from different areas endemic for visceral leishmaniasis (VL) as a prerequisite for the design of effective control strategies against the disease.Methodology/Principal FindingsSixty-three strains of L. donovani newly isolated from VL cases in the two main Ethiopian foci, in the north Ethiopia (NE) and south Ethiopia (SE) of the country were investigated by using 14 highly polymorphic microsatellite markers. The microsatellite profiles of 60 previously analysed L. donovani strains from Sudan, Kenya and India were included for comparison. Multilocus microsatellite typing placed strains from SE and Kenya (n = 30) in one population and strains from NE and Sudan (n = 65) in another. These two East African populations corresponded to the areas of distribution of two different sand fly vectors. In NE and Sudan Phlebotomus orientalis has been implicated to transmit the parasites and in SE and Kenya P. martini. The genetic differences between parasites from NE and SE are also congruent with some phenotypic differences. Each of these populations was further divided into two subpopulations. Interestingly, in one of the subpopulations of the population NE we observed predominance of strains isolated from HIV-VL co-infected patients and of strains with putative hybrid genotypes. Furthermore, high inbreeding irreconcilable from strict clonal reproduction was found for strains from SE and Kenya indicating a mixed-mating system.Conclusions/SignificanceThis study identified a hierarchical population structure of L. donovani in East Africa. The existence of two main, genetically and geographically separated, populations could reflect different parasite-vector associations, different ecologies and varying host backgrounds and should be further investigated.
Highlights
In Ethiopia, it is estimated that every year more than 4,000 individuals suffer from visceral leishmaniasis (VL, otherwise called kala-azar) caused by protozoan parasites of the Leishmania donovani complex [1]
Based on the phlebotomine sand fly species involved in the transmission cycle of the parasite, two markedly different ecological situations have been recognized in East African VL foci
Using a highly discriminatory multilocus microsatellite typing approach, we found a remarkably high genetic diversity among the East African strains of L. donovani studied which grouped into two genetically and geographically distinct populations comprising parasites from south Ethiopia (SE) and Kenya, and those from north Ethiopia (NE) and Sudan
Summary
In Ethiopia, it is estimated that every year more than 4,000 individuals suffer from visceral leishmaniasis (VL, otherwise called kala-azar) caused by protozoan parasites of the Leishmania donovani complex [1]. Studies elsewhere showed that differences in the biology and ecology of sand fly vectors may influence the genetic make-up of the Leishmania parasite populations they harbor and transmit [10]. One could hypothesize that at least two genetically distinct populations of parasites of the L. donovani complex should be present in East Africa corresponding to the different vector species. This remains to be proven by analysing strains of L. donovani from the two ecotypes of VL in East Africa. The aim of this study was to describe the population structure of Ethiopian strains of Leishmania donovani derived from different areas endemic for visceral leishmaniasis (VL) as a prerequisite for the design of effective control strategies against the disease
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