ABSTRACT
The genus Anaplasma encompasses several obligately intracellular bacterial species (e.g., Anaplasma phagocytophilum, A. marginale, A. centrale, A. bovis and A. platys) that are classiŠed in the family Anaplasmataceae, order Rickettsiales. While Anaplasma phagocytophilum infects the neutrophils of ruminants (previously referred to as Ehrlichia phagocytophila), equines (Ehrlichia equi), and humans (HGE agent) (Figure 52.1);2 A. marginale, A. centrale, A. bovis and A. platys are essentially animal pathogens, which are beyond the scope of this chapter. The type strain of A. phagocytophilum is strain Webster. Different isolates of A. phagocytophilum are causative agents of tick-borne fever in sheep, cattle, and goats; equine granulocytic anaplasmosis; canine granulocytic anaplasmosis; and human granulocytic anaplasmosis. They exhibit a variety of speciŠc features and host adaptations, which have been summarized in several reviews.2-7 For the purpose of the current review, the scope of this chapter is limited to description of the agent of human granulocytic anaplasmosis (HGA) and the clinical characteristics of this disease.
