Infertility associated with Eperythrozoon wenyonii infection in a bull

A 16-month-old Charolais bull was examined because of acute onset of scrotal and hind limb edema, fever, tachycardia, tachypnea, anorexia, and lethargy. Scrotal circumference on initial examination was 48 cm. Clinicopathologic abnormalities included microcytic, normochromic anemia and numerous Eperythrozoon organisms in blood smears. Results of immunohistochemical staining of a skin biopsy specimen suggested that the edema was the result of an Arthus-type reaction. Semen quality deteriorated rapidly, and the bull was aspermic within 7 days. The bull was treated with oxytetracycline, and the anemia and edema gradually subsided. Eperythrozoon organisms were not detected in blood smears after 3 days. Six months after initial examination, results of physical examination and semen evaluation were normal. We hypothesize that scrotal edema caused failure of testicular thermoregulation, resulting in transient production of abnormal sperm and infertility.