Distribution of Leptospira interrogans by Multispacer Sequence Typing in Urban Norway Rats (Rattus norvegicus): A Survey in France in 2011-2013

Background

Urban leptospirosis has increasingly been reported in both developing and developed countries. The control of the disease is limited because our understanding of basic aspects of the epidemiology, including the transmission routes of leptospires among rat populations, remains incomplete. Through the ability to distinguish among Leptospira strains in rats, multispacer sequence typing (MST) could provide a modern understanding of Leptospira epidemiology; however, to our knowledge, the distribution of Leptospira strains among urban rat colonies has not been investigated using MST.

Aims and Methodology

The objective of this study was to identify the Leptospira strains present in rats (Rattus norvegicus) in Lyon (France) using MST and to characterize their spatial distribution. Kidneys and urine were collected from rats trapped live in seven locations in the city and in one suburban location. Each location was considered to represent a rat colony. Bacterial cultures and quantitative polymerase chain reaction (qPCR) assays were performed, and the L. interrogans DNA identified was then genotyped using MST. The distributions of Leptospira strains were spatially described.

Key Results

Among 84 wild rats, MST profiles were obtained in 35 of 37 rats that had a positive result for L. interrogans by bacterial culture and/or qPCR analyses. All of the MST profiles were related to reference strains previously isolated from human patients that belong to the serogroup Icterohaemorrhagiae and the serovars strain(s)] Copenhageni Wijinberg or M20] (n = 26), Icterohaemorrhagiae CHU Réunion] (n = 7), Icterohaemorrhagiae R1] (n = 1) and Copenhageni Shibaura 9] (n = 1). Each colony was infected with leptospires having the same MST profile.

Major Conclusions

This study demonstrated that MST could be used for the purpose of field studies, either on culture isolates or on DNA extracted from kidneys and urine, to distinguish among L. interrogans isolates in rats. MST could thus be used to monitor their distributions in urban rats from the same city, thereby providing new knowledge that could be applied to explore the circulation of L. interrogans infection in rat colonies. Because the strains are related to those previously found in humans, this application of MST could aid in the source tracking of human leptospirosis, and the findings would be relevant for public health purposes according to the One Health principle.