Brucellosis as an occupational disease: a study of an airborne-spread outbreak at a slaughterhouse

Abstract

Background: The onset of a large number of cases of brucellosis among employees at a slaughterhouse in Zaragoza where sheep from livestock culling procedures were being slaughtered, led to an investigation being made for the purpose of shedding light on the cause of this outbreak. Methods: This study was organized into three parts: 1) Description of the outbreak 2) Study of the slaughterhouse layout and activity as regards the number of animals slaughtered, the employee workload and the degree of risk involved in each working area and 3) Unmatched case-control study. Results: No significant differences were found among the attack rates by the sections of the slaughterhouse where the employees in question worked. The slaughtering analysis revealed a concomitant fluctuation between the slaughter of culled sheep and the epidemic. The case-control study revealed no significant differences for the risk factors involving working in a risk area, the use of protective measures and cuts/wounds. Conclusions: This outbreak is related to the slaughter of culled sheep. The fact that no significant difference were found by sections or due to working in a risk area is compatible with an overall explanation. Nor were any differences among the employees found to exist with regard to cuts/wounds or the use of protective measures, which focuses importance on airborne spread.