PMID: 7545504Jan 1, 1993Paper

Trypanosoma and Leishmania have clonal population structures of epidemiological significance

Biological Research
F J Ayala

Abstract

This paper presents three results concerning the population structure of Trypanosoma cruzi, the agent of Chagas disease: (1) The mode of propagation of T. cruzi in nature is clonal; sexual reproduction is either totally absent or so rare that it leaves no traces in the population structure of the parasite. (2) The genetic diversity of the clonal lineages is large: extant T. cruzi represent lineages of descent that have evolved independently for long time spans (up to 40 million years). (3) Some genetically identical clonal lineages ("clonets") are geographically widespread ("ubiquitous"). However, most clonets are endemic, restricted in geographic distribution. These results have each in turn consequences of epidemiological significance: (1) In a sexually-reproducing organism the individual genotype is ephemeral; the entity that persists and evolves is the species ("gene pool"), and a few individuals contain most of the genetic variability of the species. In a clonally-propagating organism, the entity that persists and evolves is the clonal lineage; the genetic diversity of the species can only be captured by extensive sampling of distinct lineages. (2) The extensive genetic divergence among clonal lineages implies proportional...Continue Reading

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