can be contracted at any time, but major dissemination is at or immediately following calving. Milk from an infected cow contains brucella organisms off and on throughout lactation. Calves receiving milk from infected cows shed live organisms in their feces. It is possible, but unlikely, for an infected bull to transmit the disease to a cow during breeding. Brucella abortus is very susceptible to disinfectants, the action of sunlight and drying. Decay of contaminated material destroys the organism quickly. However, brucella organisms may remain viable for several months if the environment remains cool, moist and dark. A late-term abortion is easily recognized. However, brucellosis doesn't consistently result in abortion, and there are several important causes of abortion other than brucellosis. Several laboratory procedures are useful in a differential diagnosis. Brucella organisms may be recovered from an aborted fetus, placenta, uterine discharge, milk, semen or abscess. Tests may be conducted with blood serum, vaginal mucus, milk, whey or semen. The card test, which uses disposable components, is used to screen blood samples when results are needed immediately. Tests are a reliable means of identifying infected animals and herds. All tests are not absolute and it is, therefore, necessary that they be graded by degree of reaction and carefully interpreted. Herd test results are most meaningful when they can be compared with previous herd tests that have been kept on record. Individual cattle tested and found negative must be retested after a minimum of 60 days before one can be relatively confident they are free of brucellosis. Laboratory tests are available to help diagnose other important diseases which affect reproduction and which may be confused with brucellosis. Over 11 percent of all cattle herds in the United States were infected with brucellosis in 1934. Through concerted application of available testing and vaccination procedures, fewer than 1/2 of 1 percent of the nation's cattle are now infected. Success in reducing the incidence of brucellosis has not been uniform. There was a 42 percent reduction of this disease in cattle in the nation as a whole, but only 11 percent reduction in the South between 1967 and 1973. Five southern states in 1984 still had an infection rate exceeding 1 percent of herds tested. Brucellosis must be regarded as a real and constant threat until it is completely eradicated. Most herd infections begin by purchase of infected or exposed cattle. However, brucellosis may enter a herd from a neighboring farm via a diseased placenta, aborted fetus, or intermingling of cattle. A single test of an animal from an uncertain source is not enough to prevent the introduction of brucellosis into a herd. Herd additions should come from known negative herds, be isolated for a minimum of 60 days and be retested. Herd certification (an annual herd test) plus the purchase of only negative animals from known negative herds provides the best assurance of avoiding brucellosis.

Immunization Vaccination can be a very helpful tool in maintaining herd resistance to brucellosis. Vaccination also facilitates movement of female cattle to several states. Although no animal can be considered totally immune to severe exposure, two-thirds of cattle properly vaccinated will resist most exposures.