Leptospirosis is an epidemic-prone zoonotic disease that occurs worldwide. In Central America, leptospirosis outbreaks have been reported in almost all countries; Nicaragua in particular has faced several outbreaks. The objective of this study was to stratify the risk and identify “critical areas” for leptospirosis outbreaks in Nicaragua, and to perform an exploratory analysis of potential “drivers”. This ecological study includes the entire country (153 municipalities). Cases from 2004 to 2010 were obtained from the country’s health information system, demographic and socioeconomic variables from its Census, and environmental data from external sources. Criteria for risk stratification of leptospirosis were defined. Nicaragua reported 1,980 cases of leptospirosis during this period, with the highest percentage of cases (26.36%) in León, followed by Chinandega (15.35%). Among the 153 municipalities, 48 were considered critical areas, 85 were endemic and 20 silent. Using spatial and statistical analysis, the variable presenting the most evident pattern of association with critical areas defined by top quintile of incidence rate is the percentage of municipal surface occupied by the soil combination of cambisol (over pyroclastic and lava bedrock) and andosol (over a volcanic ashes foundation). Precipitation and percentage of rural population are also associated with critical areas. This methodology and findings could be used for Nicaragua’s Leptospirosis Intersectoral Plan, and to identify possible risk areas in other countries with similar drivers.

Leptospirosis is an epidemic-prone zoonotic disease that occurs worldwide, with more than 500,000 human cases reported annually. It is influenced by environmental and socioeconomic factors that affect the occurrence of outbreaks and the incidence of the disease. Critical areas and potential drivers for leptospirosis outbreaks have been identified in Nicaragua, where several conditions converge and create an appropriate scenario for the development of leptospirosis. The objectives of this study were to explore possible socioeconomic variables related to leptospirosis critical areas and to construct and validate a vulnerability index based on municipal socioeconomic indicators. Municipalities with lower socioeconomic status (greater unsatisfied basic needs for quality of the household and for sanitary services, and higher extreme poverty and illiteracy rates) were identified with the highest leptospirosis rates. The municipalities with highest local vulnerability index should be the priority for intervention. A distinction between risk given by environmental factors and vulnerability to risk given by socioeconomic conditions was shown as important, which also applies to the “causes of outbreaks” and “causes of cases”.

RESUMEN Objetivo El objetivo de este estudio fue conocer las características epidemiológicas de la leptospirosis en animales domésticos y en los casos de leptospirosis humana en áreas peridomésticas en Nicaragua entre 2014 y 2016. Métodos Las muestras se extrajeron en áreas donde se confirmaron casos en humanos utilizando un muestreo no probabilístico en 10 de los 17 departamentos del país. Se incluyeron 112 muestras de orina de animales domésticos, 129 muestras de agua y 69 de tierra para aislar leptospiras en medio Ellinghausen-McCullough-Johnson-Harris (EMJH). Además, se aplicó la prueba de microaglutinación (MAT) en 263 muestras de suero de animales y 88 aislados se analizaron mediante PCR. Resultados En 32,6% (101/310) de las muestras se aislaron espiroquetas, 23,2% (26/112) se aislaron en la orina de animales domésticos, 47,3% (61/129), en las muestras de agua y 20,3 % (14/69), en las de tierra. El análisis de aislamiento mostró diferencias significativas (P < 0,05) entre los departamentos para los diferentes tipos de muestras, y el aislamiento fue más frecuente en agua que en tierra (OR = 3,49; IC95%: 1,56-7,80). El 14,1% (37/263) de los animales fueron reactores en la prueba de microaglutinación. El serogrupo más frecuente fue Icterohaemorrhagiae (40%). En el análisis con la PCR para identificar leptospiras de las especies patógenas 10,2% (9/88) de los aislamientos fueron positivos. Conclusiones Esta investigación demuestra que los animales domésticos y el ambiente desempeñan un papel importante en la aparición de brotes de la leptospirosis y confirma el comportamiento endémico de la enfermedad en Nicaragua.