An epidemiological survey of human brucellosis in three Victorian abattoirs.

During the period 1977-1978, a serological and epidemiological investigation was conducted by the Victorian Departments of Health and Agriculture to determine the risk to abattoir workers of exposure to Brucella abortus from infected cattle. Nearly 1000 specimens of serum from workers at three abattoirs were tested for brucella antibodies at the Microbiological Diagnostic Unit. Serum agglutination and antihuman globulin tests were performed by a microtitre technique. Approximately 25% of these specimens gave positive results, with a wide variation in frequency in different abattoirs. Data relating to personal, employment and medical history were obtained by means of questionnaires. An attempt was made to identify risk factors by analysis of this information and the serological results. Within each abattoir, the presence of detectable antibodies was no more likely in people with symptoms than in asymptomatic people working in the same abattoir. However, the proportion of workers with symptoms was much higher in two abattoirs with a relatively high percentage of seropositive workers, than in a third, in which the percentage was comparatively low. There was evidence that the risk of exposure to B. abortus correlated with the percentage of cows in the total yearly "kill" for each abattoir.