ABSTRACT
This chapter concerns only with the phylogeny of the groups, discussion will be limited to reviewing the material relating to the organisms themselves, their geographical distribution, their vertebrate and arthropod host relationships, and their relationships to other microorganisms. The Anaplasmataceae have been included in the Rickettsiales on the basis of their apparent similarity to other members of the order rather than on any antigenic or phylogenie relationships. The relationship of Anaplasma to Paranaplasma is not at all clear. The separation into distinct genera on morphological grounds may not be phylogenetically sound or as useful among the prokaryotes as it is among the eukaryotes. Anaplasma has a definite biological relationship with certain ticks, but there is some question that ticks are actually essential to its maintenance in nature. The history of Haemobartonella and Eperythrozoon and a review of the early literature are given by Weinman. Haemobartonella organisms are obligate parasites tightly attached to or in vacuoles in erythrocytes of vertebrates.
