Forest-river interfaces shape lobomycosis risk in the Amazon Basin

Lobomycosis is a chronic implantation mycosis caused by the uncultivable fungus Paracoccidioides lobogeorgii. The disease occurs predominantly in the Amazon Basin and has traditionally been associated with traumatic inoculation during exposure to forest environments. However, many patients live, work, or travel in riverine landscapes, suggesting that environmental determinants beyond forest exposure may influence the spatial occurrence of disease.

We conducted a spatial case-background study including 192 confirmed lobomycosis cases and two environmental background locations per case. Using annual land use and land cover data aligned with the estimated year of infection, we quantified the composition and configuration of forests and water bodies at two spatial scales: 3 km2 and 10 km2. Generalized additive models were used to assess associations between environmental variables and lobomycosis occurrence while accounting for spatial structure. Models incorporating landscape configuration outperformed those based on landscape composition alone. Water-body dominance, measured by the largest patch index, and proximity to rivers were associated with lobomycosis occurrence, supporting a role for forest-river interfaces in the spatial distribution of disease.

These findings suggest that lobomycosis occurrence in the Amazon is shaped not only by forest cover but also by the spatial configuration of forest and aquatic environments. Forest-river interfaces may represent ecological and human activity zones where environmental suitability and exposure opportunities overlap. These results provide new insights into the environmental ecology of lobomycosis and may help guide surveillance and prevention strategies in riverine Amazonian landscapes.