Genetic diversity of Leishmania tropica in Morocco: does the dominance of one haplotype signify its fitness in both predominantly anthropophilic Phlebotomus sergenti and human beings?

摘要

In Morocco, cutaneous leishmaniasis (CL) caused by Leishmania tropica is endemic to locations where the predominantly anthropophilic blood-feeding Phlebotomus sergenti and humans co-perpetuate. The objective of this study was to explore whether the range of epidemiological features of CLcould be linked to the range of L. tropica genetic heterogeneity and to further explore the relationships between the genetic diversity of L. tropica in both P. sergenti and humans. L. tropica DNAwas extracted from dermal scarping smears of 125 CLpatients. Genetic polymorphisms were analyzed by sequencing the internal transcribed spacer (ITS) 1 and 5.8S rDNAgene. Nucleotide diversity (pi), haplotype diversity (Hd) and Tajima's D test for neutrality, as well as overall and pairwise FSTvalues, were calculated using Arlequin ver 3.5 software. Out of the 125 amplified DNAsequences, 93 were completely sequenced and 13 L. tropica haplotypes were identified, which confirmed the significant genetic heterogeneity of L. tropica in Morocco. The most common haplotype included 74 out of 93 sequences; this haplotype is not only widely represented but was also detected in P. sergenti, which is known to be the most abundant species in the studied foci. Considering the negative value calculated using Tajima's D index, we briefly discussed the hypothesis that the L. tropica common haplotype propagation could be a sign of its fitness in P. sergenti and human hosts. Furthermore, analysis of molecular variance (AMOVA) shows significant correlations between intraspecific variants of L. tropica and patients' geographic origins. The long-term goals of the present pilot study are to further explore the relationships between the genetic diversity of L. tropica in human and P. sergenti populations.