Browsing by Subject "Echinococcu"

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Genetische Diversität von Echinococcus granulosus sensu stricto
(2017) Ebi, Dennis; Mackenstedt, Ute
The dog tapeworm Echinococcus granulosus sensu stricto, distributed worldwide, is the most important agent of human Cystic Echinococcosis, a zoonotic disease which is considered as one of the priority ‘neglected zoonotic diseases’ by the World Health Organisation. The parasite is known from a large number of host species and is conventionally subdivided into several genotypes. The epidemiological consequences of the variation, however, are still unknown. In the last years several studies on the intraspecific variation of this parasite were published. Most of these studies were based on small numbers of isolates from geographically restricted regions, so that the relevance of that diversity concerning pathogenicity, host specificity, transmission cycles and biogeography is still little understood. To achieve a comprehensive estimate of its genetic diversity, 1085 isolates of E. granulosus s.s. from humans and animal hosts originating from widely different regions of the world were analyzed for the sequence polymorphism of a 1609 bp fragment of the mitochondrial cox1 gene. For analysis haplotype networks, diversity and neutrality indices of subpopulations of different geographic origin were compared. To improve the analytical efficiency of the sequence-data, a LabVIEW application was written. It could be shown that most diverse sub-population is found in the Middle Eastern region and that the genetic diversity is lower in the other analyzed regions, which confirms a previous tentative hypothesis on the origin of the domestic cycle of E. granulosus s.s. in that region. Records of identical haplotypes in different regions, inclusion of published data, calculation of parameters of population genetics and haplotype network analysis led to hypotheses explaining the distribution history of E. granulosus s.s.. This in line with fossil and molecular data on domestic sheep as the principal final host. A set of new and easily calculable genetic diversity indices were developed and their added value was explained. Additionally, a statistical resampling experiment was programmed which showed that at least 40 well distributed samples are necessary to provide a reliable estimate of the genetic diversity of the parasite in a region. Using an extension for that software, it was shown that the newly developed diversity indices do not strongly depend on the number of analyzed samples, and provide appropriate tools to assess the genetic diversity of parasite populations.