Abstract
Simple SummaryLeptospirosis is a zoonosis caused by pathogenic Leptospira, and synanthropic and wildlife species of rodents are an important source of infection; however, much of the information about the progression of the infection was obtained from lab murine models. The aim of this study was to assess infection status and risk factors by pathogenic Leptospira in synanthropic and wild rodent species and describe histopathological lesions in several organs from naturally infected animals. In this study, 121 rodents from three synanthropic species and two wild species were trapped within dairy farms in Southern Chile, where the bacteria were present. Liver, heart, kidney, and lungs from trapped animals were analyzed by different techniques to detect if the lesions present were produced by the bacteria. A large proportion of animals were identified as infected that were not detected by the microscopic agglutination test. There is a lower risk of infection in the fall compared to the rest of the seasons, and the synanthropic species has a lower risk of infection in comparison with wildlife species. Immunohistochemistry and quantitative real-time lipL32 polymerase chain reaction contributed to identifying the presence of pathogenic Leptospira in related histological lesions and 50% more infections than serology.Leptospirosis is caused by pathogenic Leptospira, and synanthropic and wildlife species of rodents are an important source of infection; however, much of the information about infection progression was obtained from murine models. The aim of this study was to assess infection status and risk factors associated with pathogenic Leptospira in synanthropic and wild rodent species and describe histopathological lesions in several organs from naturally infected animals. In a cross-sectional study, 121 rodents from three synanthropic species and two wild species were trapped in dairy farms in Southern Chile. Liver, heart, kidney, and lungs from trapped animals were fixed in formalin and stained with hematoxylin–eosin. Tissues with lesions consistent with Leptospira infection were tested by immunohistochemistry (IHC) and real-time polymerase chain reaction (qPCR) using the LipL32 antigen. Risk factors were assessed by a conditional mixed-logistic regression model. More than half (56.7%) of the negative reactors to the microscopic agglutination test were identified as infected either by IHC/qPCR. A lower risk of infection compared to the rest of the seasons was found in the fall, and the synanthropic species have a lower risk of infection in comparison with the wildlife species. IHC and qPCR contributed to the identification of pathogenic Leptospira in related histological lesions and 50% more infections than serology.
Highlights
Leptospirosis is one of the most widespread zoonotic diseases caused by infection with pathogenic spirochetes of the Leptospira genus [1]
The results suggest that during the fall, a lower risk of infection in comparison with the rest of the year was observed, and the synanthropic species had a lower risk of infection in comparison with wildlife species, which was an unexpected but interesting finding
This study reports the infection status and describes histological lesions in synanthropic and wild species of rodents naturally infected with pathogenic Leptospira, which were captured in dairy farms in the Los Ríos Region in Southern Chile
Summary
Leptospirosis is one of the most widespread zoonotic diseases caused by infection with pathogenic spirochetes of the Leptospira genus [1]. Human patients usually present with a nonspecific self-limiting febrile illness; a variable proportion of cases develop a severe disease called Weil’s disease, which is characterized by jaundice, acute renal failure, hemorrhagic diathesis, and severe pulmonary hemorrhagic syndrome (SPHS) [2]. The main burden of leptospirosis is caused by severe disease forms and can vary among countries. In countries in which leptospirosis is endemic, case fatality from Weil’s disease is >10% and >50% for SPHS [2,3]. Synanthropic rodents (Rattus norvegicus (RN), R. rattus (RR), and Mus musculus (MM)) are considered important sources of infection by pathogenic Leptospira, among which RN is the main host of L. interrogans serovar Copenhageni, which is one of the most pathogenic Leptospira species for human infections [4]. Other important sources of infection for humans are domestic dogs, cattle, horses, sheep, and goats [1]. Rodents are persistent renal carriers but rarely develop signs of the infection [5]
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