In February 1985, a 2-year-old bull with inappetence and weight loss of 1-week duration was examined by the field services staff of the Iowa State University College of Veterinary Medicine. The bull had a normal rectal temperature, decreased rumen activity, and loose feces and walked with a stiff gait. The hemogram was normal for hemoglobin concentration, PCV, and total plasma protein concentration, but the bull had a leukopenia which was primarily attributable to an absolute lymphopenia. Treatment consisted of antimicrobial drugs, an antidiarrheal medication, and a nonsteroidal anti-inflammatory and analgesic drug. After 3 weeks without improvement, the bull was admitted to the Iowa State University Large Animal Hospital
