Rickettsial agent of disease, which occurs as small 0.2–0.5 μm sized spheres singly or in chains on the surface of red blood cells of dogs. Similar stages in cats have been described as H. felis (syn. Eperythrocytozoon felis). They are ingested during blood sucking of Haemaphysalis leachi ticks (or related species). They are reproduced inside the intestine, are excreted with the feces, and thus reach the skin of hosts, where they may enter the body via wounds during scratching. Since erythrocytes may become destroyed, haemobartonellosis is always connected with anemia and apathia of infected dogs. Treatment of this disease can be done with doxycycline or imidocarb.