Pathogenic Leptospira Species Are Present in Urban Rats in Sydney, Australia

Abstract

Leptospirosis is an emerging disease among people and dogs in Sydney, Australia. However, the routes of Leptospira transmission in these cases, and in particular the possible role of rats as reservoirs of infection in Sydney, are unknown. Rats were collected within the City of Sydney Council area and their kidneys were tested for pathogenic Leptospira DNA by real-time (q)PCR. A subset of rats also had qPCR testing performed on whole blood and urine, and Microscopic Agglutination Testing (MAT) that included a panel of 10 Leptospira serovars from nine different Leptospira serogroups was performed on a subset of serum samples. Based on qPCR testing, the proportion of rats with Leptospira DNA in their kidneys was 9/111 (8.1%). qPCR testing of blood samples (n = 9) and urine (n = 4) was negative. None of the 10 serum samples tested MAT positive. A primary cluster of qPCR-positive locations was detected based on six infected rats, which partially overlapped with a previously identified cluster of canine leptospirosis cases in Sydney. These findings suggest that rats in Sydney might play a role in the transmission of leptospirosis to dogs and people. Further testing of rats in Sydney and investigation into other possible wildlife reservoirs of infection and environmental sources of leptospires are needed.

Are Pathogenic Leptospira Species Ubiquitous in Urban Recreational Parks in Sydney, Australia?

“…This result triggers several questions: is it associated with wildlife contamination, or could it indicate transmission of Lepstopira via aerosolized soil in a natural environment? In rats trapped in the City of Sydney council area, 8.1% of the sampled individuals were infected with leptospires and carried the bacteria in their kidneys, which could result in the shedding of the bacteria if individuals are chronically infected [ 61 ]. Other common Australian urban wildlife, including flying foxes [ 62 ], bandicoots [ 63 ], and possums [ 64 ], are all potential reservoirs of pathogenic Leptospira organisms.…”

Landscape, Socioeconomic, and Meteorological Risk Factors for Canine Leptospirosis in Urban Sydney (2017–2023): A Spatial and Temporal Study

“…They may cause a more significant impact in locations outside our study area. Previously, pathogenic Leptospira has been identified using PCR in 8% of sampled rats [ 8 ]. Due to the lack of knowledge about rat populations in Sydney, the presence of commercial properties (e.g., restaurants) in the SA1s was included to present neighbouring rat presence and activity [ 56 ].…”

“…Regarding urban wildlife reservoirs, rats have been the most suspected source of human leptospirosis outbreaks and the most surveyed animals due to their proximity to human households and consistent seropositivity, as well as the microbial presence of pathogenic Leptospira in locations including Sydney, Australia [ 7 , 8 , 9 , 10 , 11 ]. In Australia, the presence of Leptospira interrogans has also been detected in kangaroos [ 12 ], urban possums [ 13 ], and flying foxes [ 14 ], with evidence of urinary shedding of leptospires from flying foxes [ 15 ].…”

Older urban rats are infected with the zoonotic nematode Angiostrongylus cantonensis

“…Black ( R. rattus ) and brown ( R. norvegicus ) rats were trapped during the years of 2020 and 2021 in the City of Sydney local government area (LGA) for a leptospirosis surveillance project (University of Sydney Animal Ethics Committee approval number 2020/1725, N00/1–2013/3/5920, 2017/1130 and 2019/1665). The methodology for rat trapping, placement of traps and morphometric data collection are described in the materials and methods of the original article by Bedoya-Pérez et al (2023) . Superfluous faecal samples from the abovementioned project were provided to the University of Sydney Laboratory of Veterinary Parasitology.…”

“…Animal ethics approval for rat sampling in a separate project was granted by the Animal Ethics Committee (approval number 2020/1725, N00/1–2013/3/5920, 2017/1130 and 2019/1665). Ethics approval was obtained by Bedoya-Pérez et al (2023) .…”