Echinococcus granulosus: intraspecific genetic variation assessed by a DNArepetitive element

A 186 bp Echinococcus granulosus-specific repetitive element, TREg, was use d to assess genetic variation between strains. In G7 genotype (pig strain) it has the characteristics of a satellite DNA element with a copy number of 23 000 per haploid genome. Analysis, by sequencing of TREg monomers, showe d a great degree of identity within them. In the G I genotype (common sheep strain) TREg-like repetitive elements were found in an interspersed distri bution throughout the genome and in only 120 copies. The sequences of these monomers showed a great degree of variation between them and with TREg of G7 origin. The G6 genotype (camel strain) showed a pattern of distribution and copy number similar to the G7 genotype, and the G2 genotype (Tasmanian sheep strain) similar to the G I genotype. Isolates from the G5 (cattle str ain) and G4 (horse strain) genotypes also showed unique hybridization patte rns in Southern blot experiments. The genomic plasticity of E. granalosus, which may have important consequences in the epidemiology and control of cy stic hydatid disease is reflected in the results of this work.