Twelve unlinked microsatellite markers were used to determine the microsatellite profiles of 50 newly and 46
previously typed strains of L. tropica from various Israeli and Palestinian foci. Their microsatellite profiles were
compared to those of 99 previously typed strains of L. tropica from 15 countries. Israeli and Palestinian strains
of L. tropica fell into three different groups, one of which contained 75 of the 96 Israeli and Palestinian strains.
This population separated fromall the others at the first hierarchical level by Bayesian statistics and formed a distinct
monophyletic group on applying genetic distance and allele frequency analyses. The second cluster
contained ten Israeli strains from a specific focus north of the Sea of Galilee,whichwere previously shown to differ
from all other strains of L. tropica in their serological, biochemical and molecular biological parameters. This
clusterwas closely related to clusters comprising strains of L. tropica from Africa. Four Israeli and five Palestinian
strains fell into different genetic entities mostly related to strains from Asian foci of CL.
Importation during numerous migrations of humans and, perhaps, infected reservoir animals in the past and,
now, through modern travel is the most likely explanation for the existence of so many locally encountered genetic
variants of L. tropica in the Israeli-Palestinian region. Geographical and ecological variation may play a role
in expanding the genetic heterogeneity once given importations had become established in different foci. Currently,
one population is expanding in the area comprising almost all of the Palestinian and Israeli strains of L.
tropica isolated since 1996 and investigated in this study, which differ clearly from all other strains ofwhatsoever
origin. This population seems to result from the re-emergence of a previously existing genotype owing to environmental
changes and human activities.
