Ratting out leptospirosis: investigation of a revealing urban case associated with socioeconomic disadvantage in Sydney, Australia

Classically reported in Australia in association with travel or occupational exposures, leptospirosis in the urban setting is a disease of lower socioeconomic status with the risk of rat exposure inversely proportional to conditions of living. Whilst this has been widely reported elsewhere in the world, urban-acquired cases of leptospirosis are rare in Australia. Here we report on the fifth locally acquired case in Sydney, Australia, during the period 2003-2024. This case coincided with a severe rat infestation in the case's social housing block. A collaborative environmental health investigation followed, involving members of the Public Health Unit and Department of Primary Industries and Regional Development. Twelve rats captured within a 1.5 km radius of the case's residence underwent polymerase chain reaction testing for leptospirosis and were all negative. This prompted consideration of other potential reservoirs, including native species. This case demonstrates persisting social inequities in metropolitan Sydney, and the consequences for health.