Seroprevalence of leptospiral antibodies in rodents from riverside communities of Santa Fe, Argentina

Abstract

Background: Leptospirosis is a zoonotic disease that can be transmitted by contact with the urine of infected mammals. Rodents play a mayor role in the transmission of leptospires to humans. The province of Santa Fe reports the greatest number of cases in Argentina. Yet, in this region, there are still knowledge gaps regarding the diversity of rodent species that may be hosts of pathogenic leptospires. The aims of this study were to evaluate the presence of leptospiral antibodies in rodents from three riverside communities of Santa Fe, and to identify factors associated with leptospiral infection.

Methodology/principal findings: Each community was divided into three environmental settings based on the level of human disturbance, and sampled during two springs (Sep-Oct 2014 and 2015) and one autumn (Mar-Apr 2015). Serum samples of captured sigmodontine and murine rodents were tested for leptospiral antibodies by enzyme-linked immunosorbent assay (ELISA), and microagglutination test (MAT) was used to assess the infecting serovar in seropositive individuals. Factors influencing seropositivity were analyzed using logistic regression models. We caught 119 rodents, of which 101 serums were suitable for analysis. Most frequently trapped species were Scapteromys aquaticus, Akodon azarae and Oligoryzomys spp., with seroprevalences of 41.3%, 42.9% and 55% respectively. Seropositivity was higher in individuals with an average body condition score and in those that were sexually mature, but in the latter the differences were marginally significant.

Conclusions/significance: Our results suggest that native rodents may be playing a role in the environmental circulation of pathogenic leptospires and provide relevant information for public health policies in the area.

Fig 1. Study sites.

(A) Location of the sampling sites within the study area: center sites are depicted in magenta, border sites in orange and natural corridor sites in green. Base map indicates the location of the province of Santa Fe in Argentina and the location of the study area in the province of Santa Fe; (B) Enlarged view of the study sites within the study area; (C-E) Pictures of the study sites: center site of Los Zapallos (C), border site of Colastiné Sur (D), and natural corridor of Colastiné Sur (E). Map created using QGIS 3.0 Girona (QGIS Development Team). Landsat8 OLI/TIRS satellite imagery acquired from U.S. Geological Survey. Vector layers acquired from Natural Earth and Instituto Geográfico Nacional. Photos taken by Dr. Andrea Previtali and Dr. Tamara Ricardo.

Fig 2. Similarities in the rodent communities between study sites.

The top dendrogram shows the grouping of study sites according to Chao’s index. The left dendrogram displays phylogenetic relationships among captured rodent species. Relative abundance of rodents is depicted as a heatmap with darker shades corresponding to higher abundances.