Eco-Epidemiology of Leptospira Infection in Invasive Rats Across Mediterranean Landscapes of Central Chile.

INTRODUCTION Leptospirosis is a global zoonosis, and rodents are key maintenance hosts in many ecosystems. However, information on pathogenic Leptospira in Mediterranean-climate landscapes of Latin America remains limited. We evaluated its occurrence and associated ecological factors in invasive Rattus norvegicus and Rattus rattus across rural and natural habitats of central Chile.

Methods

Kidney samples from 821 rats captured at 31 sites between 2023 and 2025 were screened by qPCR targeting lipL32. qPCR-positive samples were further analysed by conventional PCR targeting rpoB, and successful amplicons were sequenced for species identification. Associations with qPCR positivity were evaluated separately for each rat species using a multiscale framework incorporating individual traits, local habitat characteristics, landscape composition and season.

Results

Pathogenic Leptospira DNA was detected in 23 rats (2.8%) and was more frequent in R. norvegicus (8.4%) than in R. rattus (1.4%). All 11 successfully sequenced samples were assigned to Leptospira interrogans. In R. norvegicus, qPCR positivity was positively associated with river cover, and seasonal variation differed between sexes. In R. rattus, positivity was positively associated with body length and negatively associated with woody vegetation diversity and male sex. Candidate models containing local habitat type received substantially less support for both species, although positive rats occurred in rural and natural habitats.

Conclusions

Pathogenic Leptospira occurs at low frequency in invasive rats across Mediterranean landscapes of central Chile, with associated individual and environmental factors differing between species. Species-informed surveillance incorporating environmental heterogeneity may better characterize Leptospira circulation than broad habitat classifications alone.