Abstract

The pattern of species and strain variation within the genus Echinococcus is complex and controversial. In an attempt to characterise objectively the various species and strains, the sequence of a region of the mitochondrial cytochrome c oxidase subunit I (CO1) gene was determined for 56 Echinococcus isolates. Eleven different genotypes were detected, including 7 within Echinococcus granulosus, and these were used to categorise the isolates. The 4 generally accepted Echinococcus species were clearly distinguishable using this approach. In addition, the consensus view of the strain pattern within E. granulosus, based on a variety of criteria of differentiation, was broadly upheld. Very little variation was detected within Echinococcus multilocularis. Remarkable intra-strain homogeneity was found at the DNA sequence level. This region of the rapidly evolving mitochondrial genome is useful as a marker of species and strain identity and as a preliminary indication of evolutionary divergence within the genus Echinococcus.