Pathogenic Leptospira and their animal reservoirs: testing host specificity through experimental infection

Jean-Loup Bascands,Matthieu Bringart,Marjolaine Roche,Pablo Tortosa,Colette Cordonin,Patrick Mavingui,Olivier Flores,Magali Turpin,Koussay Dellagi

doi:10.1038/s41598-020-64172-4

Abstract

Leptospirosis is caused by pathogenic Leptospira transmitted through contact with contaminated environments. Most mammalian species are infectable by Leptospira but only few act as efficient reservoir being capable of establishing long term kidney colonization and shedding Leptospira in urine. In Madagascar, a large diversity of pathogenic Leptospira display a tight specificity towards their endemic volant or terrestrial mammalian hosts. The basis of this specificity is unknown: it may indicate some genetically determined compatibility between host cells and bacteria or only reflect ecological constraints preventing contacts between specific hosts. In this study, Rattus norvegicus was experimentally infected with either Leptospira interrogans, Leptospira borgpetersenii or Leptospira mayottensis isolated from rats, bats or tenrecs, respectively. Leptospira borgpetersenii and L. mayottensis do not support renal colonization as featured by no shedding of live bacteria in urine and low level and sporadic detection of Leptospira DNA in kidneys. In contrast 2 out of the 7 R. norvegicus challenged with L. interrogans developed renal colonization and intense Leptospira shedding in urine throughout the 3 months of experimental infection. These data suggest that host-Leptospira specificity in this biodiversity hotspot is driven at least in part by genetic determinants likely resulting from long-term co-diversification processes.

Highlights

Leptospirosis is caused by pathogenic Leptospira transmitted through contact with contaminated environments
Molecular typing of Leptospira hosted by rats from Reunion Island and Seychelles have revealed the dominance of a single species, L. interrogans, represented by three Sequence Types (STs), two of them being reported in different locations worldwide[4,5]
We tested the ability of Leptospira isolates obtained from bats (L. borgpetersenii) and tenrecs (L. mayottensis), two reservoirs endemic to southwestern Indian Ocean (SWIO) islands, to replicate in a genetically different host via i.p. inoculation of these isolates in rats, a well-known Leptospira reservoir of L. interrogans worldwide including on several SWIO islands[4,5,6,15]

Summary

Introduction

Leptospirosis is caused by pathogenic Leptospira transmitted through contact with contaminated environments. In Madagascar, a large diversity of pathogenic Leptospira display a tight specificity towards their endemic volant or terrestrial mammalian hosts. The basis of this specificity is unknown: it may indicate some genetically determined compatibility between host cells and bacteria or only reflect ecological constraints preventing contacts between specific hosts. In contrast 2 out of the 7 R. norvegicus challenged with L. interrogans developed renal colonization and intense Leptospira shedding in urine throughout the 3 months of experimental infection. These data suggest that host-Leptospira specificity in this biodiversity hotspot is driven at least in part by genetic determinants likely resulting from longterm co-diversification processes. In Tanzania, unique lineages of L. borgpetersenii, different from references sequences, are found in cattle, while L. kirschneri can be found in several ruminant species[9]

Methods

Results

Conclusion