On the other hard, splenectomized human beings had a more severe type of ehrlichiosis than non-splenectomized patients (RABINSTEIN et al., 2000), probably because there is a reduction in the antigen's clearance, a decrease in responses against new antigens, and a decrease in phagocytosis and in other protective responses (DAVIDSON; WALL, 2001). These different spleen functions against pathogenic agents could be due to multiple differences in the structure and function of the organ in the species, as suggested by Bowdler (2002).