Rodent Reservoirs of Pathogenic Leptospira in Madagascar: Investigating Risk Factors for Infection and Renal Carriage in Rattus rattus

Abstract

Leptospirosis is a neglected zoonotic disease of global concern, primarily transmitted by rodent reservoirs. In Madagascar, Leptospira spp. have been detected in both humans and small mammals, yet systematic studies remain limited, and host-level drivers of infection are poorly understood. Rattus rattus, the most widespread rodent in the country, thrives in close association with humans and agriculture, making it a likely reservoir of pathogenic Leptospira. This study aimed to estimate the prevalence of pathogenic Leptospira in Rattus rattus and evaluate whether sex, age, and body weight act as potential risk factors for infection or renal carriage. Rats were sampled from two sites in Madagascar: Betampona Natural Reserve (BET) and Kirindy-Mitea National Park (KMN). Molecular detection of pathogenic Leptospira was performed using qPCR targeting the gyrB and lipL32 genes. A generalized linear model (GLM) was used to evaluate whether host traits and sampling site predicted the odds of infection. Results indicated that 3.2% of rodents (n = 226) tested positive for pathogenic Leptospira across both sites, with higher prevalence at BET. Host traits did not significantly predict infection. This suggests that Rattus rattus may serve as a synanthropic reservoir for pathogenic Leptospira in Madagascar, although infection risk appears to be influenced more by environmental factors than by host demographics. Understanding these patterns will improve knowledge of rodent–pathogen ecology and inform prevention strategies for leptospirosis. More broadly, this work highlights the role of small mammal reservoirs in the persistence of zoonotic pathogens in tropical regions.