Eperythrozoon infection in young bulls with scrotal and hindlimb edema, a herd outbreak.

Young (9 to 10 mo) Aberdeen-Angus bulls (n = 5) in excellent body condition and pastured with approximately 35 other bulls of similar age on a farm in southeastern Alabama had fever, harsh pulmonary sounds, increased respiratory rate and variable amounts of hindlimb and scrotal edema. Bulls had mild microcytic, normochromic anemia. Numerous eperythrozoon organisms were identified on blood smears. Indirect hemagglutination inhibition test results for Eperythrozoon suis antibodies were negative either because E. suis antigens do not cross react with cattle eperythrozoon organism antibodies or blood was collected before there was sufficient time for seroconversion. Bulls had swelling of the scrotal wall, soft testes, and poor semen quality, characterized by low progressive motility and a high percentage of spermatozoa with primary and secondary abnormalities. Some of these abnormalities may be attributed to the age of the bulls. However, loss of scrotal thermoregulation was a major cause of testicular degeneration leading to poor semen quality. Other bulls in the herd had fever, increased respiratory rate, and swollen hindlimbs or scrotum. Subsequent to administration of oxytetracycline, parasitemia resolved rapidly, and clinical signs gradually abated. Four of five bulls successfully passed breeding soundness examinations six months after initial clinical illness. The remaining bull failed twice due to the presence of testicular inflammation.