Occupational Risk of Histoplasma capsulatum Exposure among Field Biologists in Ecuador: Evidence from Skin Testing and Serology

Abstract

Abstract Histoplasma capsulatum, a dimorphic fungus, is the causative agent of histoplasmosis, a respiratory disease with a wide clinical spectrum ranging from asymptomatic infection to severe pulmonary or disseminated disease. Although Ecuador is recognized as an endemic country, histoplasmosis remains underreportesd. This study presents the first investigation in Ecuador assessing occupational exposure to H. capsulatum among field biologists and environmental scientists, a group presumed to be at increased risk due to frequent contact with wildlife, caves, and rural environments. A total of 46 workers underwent histoplasmin intradermal skin testing to assess prior exposure. Positive reactions were defined as induration ≥5 mm at 48 hours. Histoplasmin positivity was detected in 21 participants (45%), with induration sizes ranging from 5 to 32 mm (mean 15 mm). Among histoplasmin-positive individuals, reported risk factors included cave visitation (83%), contact with dead animals or feces (55%), and contact with live wildlife such as bats, rodents, and birds (50%). Serological testing identified evidence of recent infection in three participants, none of whom presented clinical symptoms at the time of evaluation. Our findings demonstrate substantial occupational exposure to H. capsulatum among Ecuadorian field biologists and highlight the need for improved surveillance, diagnostic capacity, and clinical awareness of histoplasmosis in endemic, resource-limited settings.