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

Leptospirosis is an emerging disease among people and dogs in Sydney, Australia. However, the routes of 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 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 serovars from nine different serogroups was performed on a subset of serum samples. Based on qPCR testing, the proportion of rats with DNA in their kidneys was 9/111 (8.1%). qPCR testing of blood samples ( = 9) and urine ( = 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.