Predicting the Presence of Leptospires in Rodents from Environmental Indicators Opens Up Opportunities for Environmental Monitoring of Human Leptospirosis

Abstract

Leptospirosis, an environmental infectious disease of bacterial origin, is the infectious disease with the highest associated mortality in Seychelles. In small island territories, the occurrence of the disease is spatially heterogeneous and a better understanding of the environmental factors that contribute to the presence of the bacteria would help implement targeted control. The present study aimed at identifying the main environmental parameters correlated with animal reservoirs distribution and Leptospira infection in order to delineate habitats with highest prevalence. We used a previously published dataset produced from a large collection of rodents trapped during the dry and wet seasons in most habitats of Mahé, the main island of Seychelles. A land use/land cover analysis was realized in order to describe the various environments using SPOT-5 images by remote sensing (object-based image analysis). At each sampling site, landscape indices were calculated and combined with other geographical parameters together with rainfall records to be used in a multivariate statistical analysis. Several environmental factors were found to be associated with the carriage of leptospires in Rattus rattus and Rattus norvegicus, namely low elevations, fragmented landscapes, the proximity of urbanized areas, an increased distance from forests and, above all, increased precipitation in the three months preceding trapping. The analysis indicated that Leptospira renal carriage could be predicted using the species identification and a description of landscape fragmentation and rainfall, with infection prevalence being positively correlated with these two environmental variables. This model may help decision makers in implementing policies affecting urban landscapes and/or in balancing conservation efforts when designing pest control strategies that should also aim at reducing human contact with Leptospira-laden rats while limiting their impact on the autochthonous fauna.

Seroprevalence and Molecular Characterization of Leptospira spp. in Rats Captured near Pig Farms in Colombia

“…Regarding precipitation, El Valle del Cauca had the highest precipitation, which, as mentioned before, is correlated with a high prevalence of Leptospira [ 4 ]. The mean altitude of the regions showed no correlation with positivity, which matches the finding in Biscornet et al 2021 [ 29 ].…”

First Molecular Detection of Pathogens Leptospira in Common Rodent Captured in North Algeria Urban Areas

“…Consequently, Rattus Norvegicus revealed a higher prevalence than Rattus Rattus. The latter result is consistent with studies carried out in Benin [46] (Rattus Norvegicus; 27.3%, Rattus Rattus; 13.3%), Singapore (Rattus Norvegicus; 46.8%, Rattus Rattus; 10.4%) [47] and Mahé Island, Seychelles (Rattus Norvegicus; 54.0%, Rattus Rattus; 4.4%) [48]. Furthermore, our finding makes sense given that R. rattus favors dry habitats, whereas R. norvegicus favors wet habitats [49], with garbage dumps and sewers, where leptospires are found in the majority, explaining the strong association between R. norvegicus and the high prevalence of Leptospira spp.…”

Syndromic Surveillance 2.0: Emerging Global Surveillance Strategies for Infectious Disease Epidemics

“…While mosquito-borne illnesses provide several well-developed case studies, numerous other health risks, such as leptospires and Lyme disease, have been studied using remote sensing technology (Biscornet et al, 2021;Cheng et al, 2017). In this literature, one promising area of growing satellite data monitoring is in land-use change studies to map human exposure to wildlife disease reservoirs.…”