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. 2020 Sep 28;14(9):e0008662.
doi: 10.1371/journal.pntd.0008662. eCollection 2020 Sep.

Circulating genotypes of Leptospira in French Polynesia : An 9-year molecular epidemiology surveillance follow-up study

Linda Grillová  1 , Hilde Angermeier  1   2 , Marc Levy  3 , Marine Giard  4 , Stéphane Lastère  3 , Mathieu Picardeau  1
Affiliations

Circulating genotypes of Leptospira in French Polynesia : An 9-year molecular epidemiology surveillance follow-up study

Linda Grillová et al. PLoS Negl Trop Dis. .

Abstract

Background: Leptospirosis is a widespread zoonosis with global impact, particularly among vulnerable populations in resource-poor settings in tropical countries. Rodents have been considered to be the main reservoir of the disease; however, a wide variety of mammals can act as hosts as well. Here we examine the genetic diversity of Leptospira strains from biological samples of patients and animals in French Polynesia (FP) from 2011 to 2019.

Methodology/principal findings: From 2011 to 2019, we have collected 444 blood samples from patients diagnosed as having leptospirosis. The limited volume of clinical material and low amount of leptospiral DNA in blood samples led us to develop a nested PCR targeting the secY locus that enabled us to amplify and sequence 244 samples (55%). In addition, 20 Leptospira strains recovered from the blood of patients from 2002 to 2011 were sequenced and fully characterized at the serogroup level and used as reference strains for the association of different phylogenetic branches with respective serogroups. The secY sequences were compared with publicly available sequences from patients and animal reservoirs in FP (n = 79). We identified rats as the main source of infection for L. borgpetersenii serogroup Ballum and L. interrogans serogroup Icterohaemorrhagiae, dogs as the main source of infection for L. interrogans serogroup Australis, and farm pigs as the main source of infection for L. interrogans serogroups Pomona or Canicola. L. interrogans was associated with the most severe infections with 10 and 5 fatal cases due to serogroups Icterohaemorrhagiae and Australis, respectively. Mortality was significantly associated with older age (p-value < 0.001).

Conclusions/significance: We described the population dynamics of leptospires circulating among patients in FP, including two patients who were reinfected with unrelated Leptospira genotypes, and clarified the local role of the animal reservoirs in the transmission route of leptospirosis to humans. Routine Leptospira genotyping directly on biological samples should allow the epidemiological follow-up of circulating strains and assess the impact of control interventions on disease transmission.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Maximum likelihood phylogeny (1000 bootstrap replicates) of Leptospira secY sequences from patients.
The phylogeny shows the distribution of species lineages, and serogroups circulating in FP during the time span from 2002 to 2019 (n = 344). Bootstrap values are shown with the size of circles in the middle of the branches, bootstraps lower than 70 are not shown. Species, lineage and serogroup names are given by the color codes (from inner to outer circles). Serogrouping was performed on culture isolates. White color indicates that the information was not available.
Fig 2
Fig 2. Median-joining network showing different Leptospira genotypes isolated from different hosts and the number of mutational differences among them.
The number of mutations, when > 1, is given adjacent to branches (in red). Inferred allelic variants (median vectors) are shown as small black connecting circles. If contiguous, indels were considered as single events only. The numbers of individuals, when > 1, are shown inside circles and are indicated by circle size. The color code indicates the host. Genotypes (in bold) and lineages are shown adjacent to the associated haplotypes.
Fig 3
Fig 3. Muller diagram—Proportions of genotypes infecting human hosts in Tahiti during the 18-year sampling framework (lower panel).
The most prevalent genotypes are highlighted. The bar chart (upper panel) is showing the number of samples sequenced in each year.
See this image and copyright information in PMC

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Grants and funding

This work was financially supported by a PTR grant (PTR30-17) from the Institut Pasteur (MP, LG) and the European Programme for Public Health Microbiology (EUPHEM) of the European Centre for Disease Prevention and Control (HA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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