Brucella infections in Illinois veterinarians.

Serums collected from Illinois veterinarians at 6 state conventions between 1956 and 1972 were tested for Brucella antibodies, with 70 of 394 (17.8%) samples reactive. Interviews with 1,261 veterinarians in 1967 and 1968 yielded 175 (13.9%) with a history of a prior clinical illness diagnosed as brucellosis. When duplicates were eliminated, there was a 17.0% (224/1,315) infection ratio. The prevalence of infection was found to be decreasing, as reflected by decreasing serologic reactor rates and by decreasing numbers of clinical diagnoses during the period. Strain 19 brucella vaccine appeared to be increasing in relative importance as a source of infection for veterinarians. Most of the small animal practitioners with a history of clinical brucellosis had been infected either as students or in an earlier practice type. Onset of clinical illness occurred the year of graduation for 21 (13%) veterinarians, with 62% between 4 years before and 4 years after graduation. Part of the explanation for the decreasing infection rates following graduation might have been the existence of a group of veterinarians at high risk of infection because of personal habits. Early infection, because of their high risk, would have resulted in rapid depletion of susceptible individuals from this group. As a result, in a few years the infection rate of the total veterinary population would no longer be dominated by this high risk group but would more nearly reflect the infection probability for the average veterinarian. There was no significant difference in death rates or cause of death between infected and noninfected veterinarians.