Ehrlichiosis may be a significant unrecognized clinical disease in cats. An infected cat may exhibit fever, lack of appetite, lack of energy, pain, and decreased red blood cell count. Although a form of Ehrlichia has been found in feline cells, it is not known which species is causing disease in cats. Since one species of Ehrlichia is the cause of human ehrlichiosis, the potential for disease transmission between cats and humans is a valid concern. The goal of this project is to isolate and characterize the disease-causing form of Ehrlichia using newly available techniques.