Incidence and Distribution of Brucella abortus in Slaughtered Bang's Reactor Cattle

In considering the occurrence of brucellosis in packing-house workers, the Bang's reactor cow has received inadequate attention. It has been frequently stated that in reactor cattle the organism is found mainly in the uterus and the udder; hence, the remainder of the carcass provides little or no exposure hazard to the worker. The prevalence of this view is somewhat surprising. It has long been known that early in the course of the disease the organism may be widely disseminated (1). Brucella has been isolated from the blood stream of cattle in a number of studies (2, 3, 4). Recently, Manthie and Carter performed blood cultures on artificially infected cattle (5). Of 270 cows, Brucella abortus was recovered from the blood of 172 animals. In 18 animals studied over a prolonged period, bloodstream infection persisted in over 80 percent for 5 months and in one animal for almost 2 years. These studies suggest an exposure hazard greater than that usually recognized. More definitive information seemed to be needed on the extent of infection in a substantial number of animals actually sent for slaughter. In this study the carcasses of 100 Bang's reactor cattle were examined. Materials and Methods To conduct the study, arrangements were made with one of the large packing plants in the Chicago area. Over a period of 6 months, 100 Bang's reactor cattle sent for slaughter were examined. They were unselected except for the known positive Bang's reaction. They were all of dairy breeds. The series comprised 88 cows, 9 heifers, 2 calves, and 1 bull. They were derived from herds in five Midwestern States. During bleeding, a blood sample was obtained for an agglutination test. At various stages of the dressing process, tissues were obtained for culture. Accessible lymph nodes in widespread areas of the carcass, tonsil, and sections of liver, spleen, uterus, and membranes and fetus, if present, were obtained. Under plant conditions, the