Echinococcus granulosus: genomic and isoenzymatic study of Spanish strains isolated from different intermediate hosts.

The phenomenon on intraspecific variation in Echinococcus granulosus is already documented in Spain, where unilocular hydatidosis is an endemic disease. The first speciation studies, focused at a genomic level, showed the existence of three different strains: ovine-bovine-human, equine and swine-caprine. In the present study, the genomic identification, by random amplified polymorphic DNA technique (RAPD) of a larger number of Spanish E. granulosus isolates, using five different primers, showed the maintenance of these groups. Thus, some of these strains may not be infective for man. These conclusions were supported by a phenotypic characterization of the same isolates by zymodeme technique, showing the five isoenzyme systems used that Spanish E. granulosus strains can also be distinguished at a phenotypic level by isoenzymatic patterns. Both techniques (RAPD and zymodemes) were used for statistical analysis and for the construction of two dendrograms, which were slightly different. In addition, some intrastrain variation was detected with both techniques, a phenomenon that is directly related to the different speciation theories proposed for E. granulosus strains. The epidemiological implications of the results are discussed in the text.