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. 2016 Aug 16;10(8):e0004895.
doi: 10.1371/journal.pntd.0004895. eCollection 2016 Aug.

Distribution and Diversity of Pathogenic Leptospira Species in Peri-domestic Surface Waters from South Central Chile

Affiliations

Distribution and Diversity of Pathogenic Leptospira Species in Peri-domestic Surface Waters from South Central Chile

Meghan R Mason et al. PLoS Negl Trop Dis. .

Abstract

Background: Leptospirosis is a neglected zoonosis affecting animals and humans caused by infection with Leptospira. The bacteria can survive outside of hosts for long periods of time in soil and water. While identification of Leptospira species from human cases and animal reservoirs are increasingly reported, little is known about the diversity of pathogenic Leptospira species in the environment and how surveillance of the environment might be used for monitoring and controlling disease.

Methods and findings: Water samples (n = 104) were collected from the peri-domestic environment of 422 households from farms, rural villages, and urban slums participating in a broader study on the eco-epidemiology of leptospirosis in the Los Rios Region, Chile, between October 2010 and April 2012. The secY region of samples, previously detected as pathogenic Leptospira by PCR, was amplified and sequenced. Sequences were aligned using ClustalW in MEGA, and a minimum spanning tree was created in PHYLOViZ using the goeBURST algorithm to assess sequence similarity. Sequences from four clinical isolates, 17 rodents, and 20 reference strains were also included in the analysis. Overall, water samples contained L. interrogans, L. kirschneri, and L. weilii, with descending frequency. All species were found in each community type. The distribution of the species differed by the season in which the water samples were obtained. There was no evidence that community-level prevalence of Leptospira in dogs, rodents, or livestock influenced pathogen diversity in the water samples.

Conclusions: This study reports the presence of pathogenic Leptospira in the peri-domestic environment of households in three community types and the differences in Leptospira diversity at the community level. Systematic environmental surveillance of Leptospira can be used for detecting changes in pathogen diversity and to identify and monitor contaminated areas where an increased risk of human infection exists.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Full Minimum Spanning Tree of sequences from surface water samples (n = 104), reference strains (n = 20), rodent kidney (n = 17), and livestock and human clinical samples (n = 4), from the Los Rios Region, Chile, 2010–2012 using the secY (202 bp) gene.
Green rectangles represent group founders and rectangles with a black border indicate nodes where multiple samples had identical sequences (two sequences each, unless otherwise noted in the legend). Samples labeled with a Leptospira species name are reference strains. For the water and rodent samples, the first letter represents the community type of origin (C = rural village, D = farm area, U = urban slum), the first number indicates the community number (1–4 for each community type), followed by the household number. The second letter indicates whether it is a water (B) or rodent (R) sequence and the last number corresponds to the sample number from a particular household. The clinical samples not already identical to other sequences and absorbed into the larger rectangles are listed by their types: Clinical-Human (blood sample) and Human-Urine.
Fig 2
Fig 2. Minimum Spanning Trees of Leptospira-positive secY sequences from surface water samples (n = 104), rodent samples (n = 17), and clinical samples (n = 4) by community type.
Community type of origin of water and rodent sequences are color coded. L. interrogans, L. kirschneri and L. weilii were found in water samples from all community types. L. borgpetersenii was found in rodents from rural farms but not in water samples.
Fig 3
Fig 3. Community-level distribution of Leptospira species from water samples collected from households in Los Rios Region, Chile.
Communities corresponded to urban slums (U), rural villages (C), and farm communities (D). Size of the pie correlates with the number of sequences available for the community.
Fig 4
Fig 4. Diagram of the theoretical framework for environmental surveillance of Leptospira.
Systematic sampling to obtain changes in presence, concentration and genotype of Leptospira could aid in detecting changes in the local epidemiology, including shifts in genetic diversity and potential increases in contamination that may lead to outbreaks.

References

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