Abstract
Leptospira spp., which comprise 3 clusters (pathogenic, saprophytic, and intermediate) that vary in pathogenicity, infect >1 million persons worldwide each year. The disease burden of the intermediate leptospires is unclear. To increase knowledge of this cluster, we used new molecular approaches to characterize Leptospira spp. in 464 samples from febrile patients in rural, semiurban, and urban communities in Ecuador; in 20 samples from nonfebrile persons in the rural community; and in 206 samples from animals in the semiurban community. We observed a higher percentage of leptospiral DNA-positive samples from febrile persons in rural (64%) versus urban (21%) and semiurban (25%) communities; no leptospires were detected in nonfebrile persons. The percentage of intermediate cluster strains in humans (96%) was higher than that of pathogenic cluster strains (4%); strains in animal samples belonged to intermediate (49%) and pathogenic (51%) clusters. Intermediate cluster strains may be causing a substantial amount of fever in coastal Ecuador.
Highlights
We observed a higher percentage of leptospiral DNA–positive samples from febrile persons in rural (64%) versus urban (21%) and semiurban (25%) communities; no leptospires were detected in nonfebrile persons
The current notion is that human leptospirosis is mainly caused by strains of the pathogenic cluster [2,4,6,9,10]
Our findings show that leptospiral DNA was present in various proportions in febrile patients living in 3 communities in Ecuador; the DNA was present in 63% of samples from persons at a rural site and in 25% and 21% of samples from persons at semiurban and urban sites, respectively
Summary
To increase knowledge of this cluster, we used new molecular approaches to characterize Leptospira spp. in 464 samples from febrile patients in rural, semiurban, and urban communities in Ecuador; in 20 samples from nonfebrile persons in the rural community; and in 206 samples from animals in the semiurban community. Many aspects of leptospirosis epidemiology remain unknown because only limited information exists regarding leptospiral population genetics and the role of environmental factors, including environmental persistence of leptospires, in disease occurrence These deficiencies in knowledge result from the complexity of the disease (e.g., many animal reservoirs carry 1 of the 14 species of potentially infectious leptospires) and technical difficulties associated with classical diagnostics, such as cumbersome isolation of bacteria from clinical samples, complex standard serologic methods, and a lack of culture techniques to obtain isolates from environmental samples. We used molecular methods to amplify and sequence the leptospiral 16S rrs gene from clinical samples from patients in 3 coastal communities in Ecuador that vary in their levels of urbanization
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