Epidemiology of Legionella Infection in Western Australia

Abstract

The population of Western Australia (WA) is concentrated mainly in the Perth metropolitan area and the coastal hinterland of the southwestern tip of the continent. Its climate is dry and warm and is described as Mediterranean. Yet Legionella infection in WA has been associated with exposure to garden products such as potting mix contaminated with L. longbeachae. The Legionella urinary antigen test is not available in WA. The majority of cases of Legionella infection are therefore diagnosed by serological means. Nucleic acid amplification methods for diagnosis of Legionella infection (a mip-based PCR protocol) were only introduced to WA in 1998 and have led to more diagnoses of L. pneumophila serogroup 1 infection than L. longbeachae infection since then, though the L. longbeachae type culture strain is negative by the mip-PCR. There was no evidence of temporal clustering of seropositive Legionella cases in WA from mid-1994 to mid-2000. During 1997, L. longbeachae was isolated from cooling tower water on three consecutive monthly samplings. Nevertheless, they suggest that the epidemiology of Legionella infection in WA is significantly different from what has been described elsewhere. The authors have been unable to find any laboratory-based evidence for the occurrence of time or space clusters of legionellosis cases in WA. Further studies into the epidemiology of Legionella infection in WA may generate useful insight into the environmental biology of this disease.