Brucellosis: re-emergence and changing epidemiology in Queensland

Abstract

Objective: To define the epidemiological and clinical characteristics of human brucellosis, which is being detected in increasing numbers of patients in Queensland.

Design and setting: Thirty-four cases of brucellosis diagnosed according to standard clinical and microbiological criteria were studied either retrospectively or prospectively over a two-year period from October 1989 to October 1991.

Results: Cases were assessed by means of standard laboratory investigations and a questionnaire documenting clinical symptoms, occupation and recreational activities, treatment and response, relapse rate and complications. Blood cultures taken from 11 patients were positive for Brucella suis; in three others, Brucella suis was cultured from other sites. In the 12 months before diagnosis, all affected individuals were involved in the killing and slaughter of feral pigs. Most infections occurred in rural Queensland but six were contracted in metropolitan Brisbane from feral pig abattoirs. All patients responded to appropriate antibiotic therapy; the relapse rate was 66% in those treated for less than four weeks. Complications (multiple splenic abscesses, epididymitis, cervical lymphadenitis and septic arthritis) occurred in four patients, who were ill for more than one month before diagnosis.

Conclusions: Brucellosis due to Brucella abortus is a disappearing disease in Australia as a result of effective eradication programs in cattle. However, the disease is re-emerging in Queensland because of recreational and occupational exposure to feral pigs infected with Brucella suis. The population at risk is increasing as the lucrative export industry based on field-shot feral pigs expands.