The epidemiology of leptospirosis and the emergence of Leptospira borgpetersenii serovar Arborea in Queensland, Australia, 1998-2004

Abstract

Leptospirosis is one of the most commonly encountered zoonoses in both Australia and the rest of the world. The incidence of leptospirosis in Queensland over the 7-year study period (1998-2004) was 3.1/100000 population. Enhanced surveillance questionnaires were used to collect patient data and facilitate an epidemiological investigation of leptospirosis in Queensland. Farming occupations comprised the majority of occupational exposure cases, however, recreational exposure accounted for 18% of the 883 cases. Rainfall and the presence of animal hosts had the most influence on the incidence of leptospirosis. Several trends in serovar numbers over this period are noted, in particular the emergence of L. borgpetersenii serovar Arborea, which accounted for 22% of all leptospirosis cases in Australia and 68% of South-East Queensland cases in 2004. Assessment of epidemiological trends in leptospirosis is important to obtain directed public health intervention and outcomes in the reduction of leptospirosis cases.

Fig. 1

Trends in the five major serovars detected in Queensland from 1998 to 2004. ■, Arborea; □, Australis; , Hardjo; , Pomona; , Zanoni.

Fig. 2

The distribution of leptospirosis cases over 30 health districts in the state of Queensland.

Fig. 3

The effect of rainfall on the incidence of leptospirosis. This data is based on the average rainfall data (□) [13] and average leptospirosis notifications (–◆–) from the Innisfail Health District over the 7-year study period.