MAINTENANCE OF BRUCELLA-ABORTUS FREE HERDS - A REVIEW WITH EMPHASIS ON THE EPIDEMIOLOGY AND THE PROBLEMS IN DIAGNOSING BRUCELLOSIS IN AREASOF LOW-PREVALENCE

This review covers some epidemiological aspects that allow Brucella to survive, spread, and maintain itself in the environment. Because the success of maintaining Brucella-free herds is determined by the effici ency of the serological tests to detect a single infected animal the l imitations of the traditional serological tests are emphasized. Serolo gical tests cannot differentiate between cattle infected with Brucella and cattle infected with microorganisms that serologically cross-reac t with B. abortus antigen. These cattle and cattle with 'natural' anti bodies jeopardize the Brucella-free status of a herd. Likewise, infect ed cattle with serologically inconclusive test results or which elude detection are also a hazard to Brucella-free herds. Since cattle that elude detection with serological tests and the presence of non-specifi c serum antibodies in healthy cattle have long been recignized as prob lems, it is opportune to reconsider the procedures currently used to d iagnose brucellosis in individual animals. Use of the skin delayed-typ e hypersensitivity test in addition to serological tests will signific antly improve the diagnosis of brucellosis. This will limit the financ ial loss incurred by outbreaks of brucellosis.