Aegyptianellosis,eperythrozoonosis, grahamellosis and haemobartonellosis

Aegyptianellosis, eperythrozoonosis, grahamellosis and haemobartonellosis are diseases caused by procaryotic microorganisms which parasitize the erythrocytes of a variety of animals. Differentiation between Eperythrozoon and Haemobartonella is difficult. The parasites are similar in the living state, being small cocci or rods. In stained preparations Eperythrozoon may appear to be annular. The major criterion for differentiation is the relation of the parasite to the erythrocyte. Haemobartonellae are tightly attached to the erythrocyte and are rarely seen free in the plasma. Eperythrozoa are loosely attached to the erthrocyte, can be readily disloded and are often seen free in the plasma. Aegyptianella which occurs intracellularly in an inclusion is easily differentiated from the others while Grahamella, which is rod shaped, is always intracellular and is not in an inclusion but is scattered throughout the erythrocyte's cytoplasm. These organisms are not generally pathogenic. A slight parasitemia, mild anemia and slight fever may follow infection in the intact animal. Most infected animals remain nonclinical carriers. Splenectomy of a carrier animal or infection of a splenectomized animal will produce high parasitemia; even then, the physiological disturbance is mild. The only exceptions to the general rule that infection with these organisms produces a mild disease in intact animals are infections with Aegyptianella pullorum, Eperythrozoon suis and Haemobartonella felis. Aegyptianella pullorum produces aegyptianellosis of fowl, a disease characterized by anemia, E. suis produces “icteroanemia of swine” and H. felis produces “filine infectious anemia”.