Ecology of Leptospira interrogans in Norway Rats (Rattus norvegicus) in an Inner-City Neighborhood of Vancouver, Canada

Abstract

Background Leptospira interrogans is a bacterial zoonosis with a worldwide distribution for which rats (Rattus spp.) are the primary reservoir in urban settings. In order to assess, monitor, and mitigate the risk to humans, it is important to understand the ecology of this pathogen in rats. The objective of this study was to characterize the ecology of L. interrogans in Norway rats (Rattus norvegicus) in an impoverished inner-city neighborhood of Vancouver, Canada.Methodology/Principal FindingsTrapping was performed in 43 city blocks, and one location within the adjacent port, over a 12 month period. Kidney samples were tested for the presence of L. interrogans using PCR and sequencing. A multivariable model was built to predict L. interrogans infection status in individual rats using season and morphometric data (e.g., weight, sex, maturity, condition, etc.) as independent variables. Spatial analysis was undertaken to identify clusters of high and low L. interrogans prevalence. The prevalence of L. interrogans varied remarkably among blocks (0–66.7%), and spatial clusters of both high and low L. interrogans prevalence were identified. In the final cluster-controlled model, characteristics associated with L. interrogans-infection in rats included weight (OR = 1.14, 95% CI = 1.07–1.20), increased internal fat (OR = 2.12, 95% CI = 1.06–4.25), and number of bite wounds (OR = 1.20, 95% CI = 0.96–1.49).Conclusions/SignificanceBecause L. interrogans prevalence varied with weight, body fat, and bite wounds, this study suggests that social structure and interactions among rats may influence transmission. The prevalence and distribution of L. interrogans in rats was also highly variable even over a short geographic distance. These factors should be considered in future risk management efforts.

An Investigation ofBartonellaspp.,Rickettsia typhi, and Seoul Hantavirus in Rats (Rattusspp.) from an Inner-City Neighborhood of Vancouver, Canada: Is Pathogen Presence a Reflection of Global and Local Rat Population Structure?

“…Additionally, the built environment within the study area is relatively homogeneous (high-density, mixed-use urban) and does not clearly account for observed heterogeneity in pathogen distribution. It is interesting to note that similar clustering was also observed for Leptospira interrogans carriage in these rat populations and likewise could not easily be explained by environmental factors or rat phenotypic characteristics (Himsworth et al 2013b).…”

“…For tissue-based PCR screening, 630 samples were considered to be the optimal sample size to calculate pathogen prevalence accurately in each city block (Himsworth et al 2013b), although additional samples were included where resources allowed. The specific samples to be tested were selected randomly.…”

High prevalence of pathogenic Leptospira in alien American mink (Neovison vison) in Patagonia

“…In this study, we found L. interrogans in Palena, Alto Rio Cisnes, and Isla Magdalena, which is a Leptospira species largely associated to rodents (Himsworth et al 2013). In addition, we found L. borgpetersenii in Liquiñe, Neltume, Lake Todos los Santos, and Alto Rio Cisnes, which is a Leptospira species associated with cattle farming.…”

Effects of Culling onLeptospira interrogansCarriage by Rats

“…The ecology of rats and the epidemiology of L. interrogans within their populations are intimately connected ( 4 ). Previous research on other reservoir species suggests that anthropogenic disturbances may alter reservoir ecology, resulting in new transmission patterns ( 5 , 6 ).…”