Quantification of Leptospira interrogans Survival in Soil and Water Microcosms

Abstract

is the etiological agent of leptospirosis, a globally distributed zoonotic disease. Human infection usually occurs through skin exposure with water and soil contaminated with the urine of chronically infected animals. In this study, we aimed to quantitatively characterize the survival of serovar Copenhageni in environmental matrices. We constructed laboratory microcosms to simulate natural conditions and determined the persistence of DNA markers in soil, mud, spring water and sewage using a quantitative PCR (qPCR) and a propidium monoazide (PMA)-qPCR assay. We found that does not survive at high concentrations in the tested matrices. No net growth was detected in any of the experimental conditions and in all cases the concentration of the DNA markers targeted decreased from the beginning of the experiment following an exponential decay with a decreasing decay rate over time. After 12 and 21 days of incubation the spiked concentration of 10 cells/ml or g decreased to approximately 100 cells/ml or g in soil and spring water microcosms, respectively. Furthermore, culturable persisted at concentrations under the limit of detection by PMA-qPCR or qPCR for at least 16 days in soil and 28 days in spring water. Altogether, our findings suggest that the environment is not a multiplication reservoir but a temporary carrier of Copenhageni, although the observed prolonged persistence at low concentrations may still enable the transmission of the disease. Leptospirosis is a zoonotic disease caused by spirochetes of the genus that primarily affects impoverished populations worldwide. Although leptospirosis is transmitted by contact with water and soil, little is known about the ability of the pathogen to survive in the environment. In this study, we quantitatively characterized the survival of in environmental microcosms and found that although it cannot multiply in water, soil or sewage, it survives for extended time periods (days to weeks depending on the matrix). The survival parameters obtained here may help to better understand the distribution of pathogenic in the environment and improve the predictions of human infection risks in areas where such infections are endemic.

Rainfall and other meteorological factors as drivers of urban transmission of leptospirosis

“…The 1 to 2 weeks lag between rainfall, temperature, or humidity and leptospirosis identified here, as well as the 2 weeks lag between rainfall and flooding reported in Manila, contrast with results from previous studies that used monthly data and suggested longer temporal association between onset of symptoms of leptospirosis and meteorological data (2 to 10month lags respectively) [18][19][20]46]. Therefore, though leptospires survive for up to one year and remain virulent in culture conditions that mimic the external environment in vitro [45,47,48], L. interrogans survival in spring water decreases to 3 weeks [49].…”

A Live Attenuated Vaccine Model Confers Cross-Protective Immunity Against Different Species ofLeptospiraspp.

“…A broad range of mammalian reservoirs harbor the spirochete in their renal tubules shedding the bacteria in their urine for long periods of time 6,7 . Leptospirosis is an environmentally-transmitted disease, for which the primary mode of transmission to humans is through contact with contaminated water or soil 8 .…”

Optimal Control of Rat-Borne Leptospirosis in an Urban Environment

“…Human leptospirosis in Salvador appears to be solely caused by L. interrogans serogroup Icterohaemorrhagiae. Such pathogenic leptospires are not known to reproduce in the environment, and survival at least of the vast majority of the population is short (Evangelista and Coburn, 2011;Casanovas-Massanaa et al, 2018). Therefore, reduction in the rodent population will, in turn, reduce the environmental load of leptospires.…”