Leishmania panamensis transmission in the domestic environment: the results of a prospective epidemiological survey in Santander, Colombia

Abstract

Introduction. Domestic transmission now appears to be the principal route of Leishmaniapanamensis infection in deforested regions characterized by the replacement of primary forestby permanent plantations, i,e coffee or cacao crops. This paper presents the results of thedisease patterns in a representative population of the Opón focus, in Santander, Colombia.Objective. The principal aims were: 1) to measure the incidence rate in a representativepopulation of the Opón focus; 2) to identify demographic risk factors for infection; 3) to estimatethe proportion of infections which cause disease; 4) to estimate the protection against diseasefrom acquired immunity; 5) to estimate the frequency of reactivations, and 6) to estimate the riskof mucosal leishmaniasis.Material and methods. A 19 month prospective survey of leishmaniasis caused by Leishmaniapanamensis was carried out amongst 1380 people in a cacao growing region of SantanderDepartment, Colombia. The population was diagnosed clinically and by the Montenegro skintest (at two time points).Results: The incidence rate was 0.19 infections/person-year, with 31% of infections apparentlysubclinical. The risk of acquiring cutaneous leishmaniasis decreased with age even in theabsence of apparent previous infections. Protective immunity followed both clinical andsubclinical infections, persisting for at least 10 years after a primary lesion. Mucocutaneousleishmaniasis was detected in 12% of the population with cutaneous lesions, of which 77% hadmild symptoms, and 23% perforated nasal septa. The risk of mucosal leishmaniasis was greatestfor males, and for people whose primary cutaneous lesion was on the head.Conclusion. The average age of infection in Opón, 7.7 years (1/l), and the absence of genderas a risk factor is highly indicative of intradomiciliary or peridomiciliary transmission