The identification of Eperythrozoon ovis in anemic sheep

Eperythrozoon ovis, a rickettsial parasite of erythrocytes, was found in anemic lambs maintained for reproductive endocrinology research. The parasite was identified in the blood films of 13 animals in the flock of 30. The sexes were infected equally (7/16 males versus 6/14 females). The relationship between the severity of the anemia and the presence of organisms in blood was statistically significant. One animal died with severe anemia. Light, scanning electron, and transmission electron microscopy of peripheral erythrocytes revealed an extracellular organism identified as E. ovis. These findings indicate that this parasite can cause disease in sheep and therefore may interfere with biomedical research.