Abstract
Human leptospirosis involves the classic epidemiological triad (agent, host and environment); hence the investigations should include the knowledge on Leptospira within the animals and the environment. The objectives of this study are to explore the abundance of Leptospira in different climate zones of Sri Lanka and to describe the presence of Leptospira in the same water source at serial time points. First, water and soil samples were collected from different parts of Sri Lanka (Component-1); second, water sampling continued only in the dry zone (Component-2). Finally, serial water sampling from ten open wells was performed at five different time points (Component-3). Quantitative PCR of water and metagenomic sequencing of soil were performed to detect Leptospira. Three replicates for each sample were used for PCR testing, and positive result of two or more replicates was defined as 'strongly positive,' and one positive replicate was defined as positive. In the water and soil sample analysis in the whole country (Component-1), two out of 12 water sites were positive, and both were situated in the wet zone. Very small quantities of the genus Leptospira were detected by 16 amplicon analysis of soil in all 11 sites. In the dry zone water sample analysis (Component-2), only samples from 6 out of 26 sites were positive, of which one site was strongly positive. In the serial sample analysis (Component-3), Six, five, four, five, and six wells were positive in serial measurements. All wells were positive for at least one time point, while only one well was positive for all five time points. Proximity to the tank and greater distances from the main road were associated with strong positive results for Leptospira (P<0.05). The presence of Leptospira was not consistent, indicating the variable abundance of Leptospira in the natural environment. This intermittent nature of positivity could be explained by the repetitive contamination by animal urine.
Highlights
Integrating the knowledge on human, animal, and environmental health is essential in controlling and predicting zoonotic diseases
Of the water samples tested from 12 sites, only the samples from Mawanella and Mathara tested positive for pathogenic Leptospira (Fig 2) in qPCR
Taxonomy assigned based on the RefSeq database via Metagenome Rapid Annotation using the Subsystem Technology (MG-RAST) showed that in the soil microbiome, the Presence of Leptospira in the environment relative abundance of the genus Leptospira was minute compared to that of other organisms
Summary
Integrating the knowledge on human, animal, and environmental health is essential in controlling and predicting zoonotic diseases. While investigations on animal and human interfaces are increasing, greater incorporation of environmental and ecosystem components is highlighted as a missing link in the One Health approach [1]. Leptospirosis, a globally widespread and neglected tropical disease, lacks adequate investigations linking animal and environmental factors to human infection. Various definitive and intermediate hosts, such as livestock, domestic pets, and wild or feral animals, harbour Leptospira in their proximal convoluted tubules of renal nephrons and excrete Leptospira via urine [2]. These excreted Leptospira enter the human body through abrasions of the skin, mucus membranes, or conjunctiva and cause leptospirosis [3]. Leptospira has acquired different mechanisms for adaptation to different environments [4]
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