HEMATOLOGIC AND SEMEN QUALITY CHANGES IN BULLS WITH EXPERIMENTAL EPERYTHROZOON INFECTION

Eperythrozoon organisms were isolated from the blood of a young beef b ull with scrotal and hindlimb edema. Young beef bulls, managed under c onditions closely mimicking those used in organized bull testing progr ams, were experimentally administered eperythrozoon organisms. Scant t o few organisms were identified on blood smears from bulls (5 of 6) fo r 2 to 4 days starting 12 days after administration. After a second ch allenge with intravenously administered viable eperythrozoon organisms , the bulb demonstrated immunity by either failing to become parasitem ic (4 of 6) or rapidly clearing the organisms from the blood (2 of 6). No bull became anemic, icteric, or hypoglycemic. Increased serum lact ate and decreased blood bicarbonate concentrations probably reflected increased glycolytic activity of infected erythrocytes. A cause for az otemia observed late in the study was not determined. The bulls did no t develop scrotal or hindlimb edema. Scrotal circumference and texture remained constant throughout the study. Semen quality was minimally a ltered while the bulls had organisms identified on blood smears. Harsh lung sounds were asculted in bulls during and immediately after organ isms were present in the blood. Although the bulls reliably had organi sms in the blood, none showed anemia, scrotal or hindlimb edema, or de creased semen quality; therefore, an additional factor or factors, or greater parasite load may be required for the expression of disease.