Leptospirosis common in tropical areas of Ecuador

Jorge Chiriboga, Verónica Barragan and others: CDC.gov
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.

Leptospirosis, caused by spirochetes of the genus Leptospira, is a neglected and potentially fatal disease that burdens impoverished communities of developing nations in tropical regions (1–4). The bacteria cause 1.7 million human cases of severe disease worldwide each year (1,2); outbreaks frequently occur during the rainy season in cities in the tropics (4–8). Domestic, peridomestic, and wild mammals harbor diverse Leptospira spp. in their kidneys, and their urine contaminates water sources and soil (6,8).

Leptospirosis is common in tropical areas of Ecuador (17). The most severe documented outbreak occurred in 1998 in Guayaquil, where 80% of case-patients required hospitalization and 12% died (J. Leake, pers. comm., 2004). During 2010–2012 in Portoviejo, Ecuador, >2,000 serologically confirmed cases of febrile leptospirosis were reported by local health authorities (M. Morales, pers. comm., 2013). 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.

Intermediate leptospires are rarely detected in humans, probably because many PCR protocols amplify genes that are present only in pathogenic species (21). Genetic characterization of Leptospira spp. makes it possible to understand disease transmission patterns and to obtain new insights by reinterpreting serologic and clinical epidemiologic data within a genetic context. Correct identification of the etiologic agent is critical for disease management in regions where dengue, malaria, leptospirosis, and, more recently, chikungunya are present (27,28). Our finding of a high number of false-positive reactions reveals the risks of using the 16S PCR (without amplicon sequencing) for diagnosis of leptospirosis. Read Article

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