Abstract
The controversial circumstances relating to the classification of the benign Theileria species from Japan, Australia and Britain, which are frequently referred to as T. sergenti/buffeli/orientalis group parasites, was reviewed. Our recent systematic comparisons suggest a possibility that the Japanese T. sergenti (minor piroplasm in common parlance) might be a new species and the Australian T. buffeli and British T. orientalis might belong to one and the same species. The necessity for the review of the genus name for these benign Theileria species was also briefly discussed after the morphological studies
of their schizogony.
