The presence of Histoplasma capsulatum in environments from the state of Nayarit, Mexico, reveals a potential risk of infection for human populations.

The Histoplasma capsulatum complex clusters cryptic species with genetic diversities linked to their geographic distribution and virulence. The American continent harbours its highest diversity, making this region the main axis for H. capsulatum spread. Species of this complex cause respiratory-systemic mycosis known as histoplasmosis. Infection occurs through the inhalation of fungal propagules that grow in sites such as caves, mines, and abandoned buildings, where environments rich in organic matter containing micronutrients present in bat and bird guano favour the development of these fungal pathogens. This research was conducted in the state of Nayarit, Mexico, where the combination of environmental factors and the constant occurrence of bats in urban and rural areas contributes to the proliferation of H. capsulatum. The presence of the fungus was detected by nested-PCR using a specific marker (Hcp100) for H. capsulatum, either in guano or in bat organ samples collected in the municipalities of Tepic, Santa María del Oro (SAMAO), and La Yesca, Nayarit. Out of 27 guano samples analysed by nested-PCR, 21 were positive for H. capsulatum, while of the 12 bats studied, only five revealed infections. The fungus was isolated from a lung sample of a nectarivorous bat (Glossophaga mutica) by culture. The results suggest a potential risk to exposed populations, including different specialized workers and tourists who explored bat roosts. Avoiding guano accumulation, restricting access to bat roosts, and implementing bat-exclusion strategies in homes are general recommendations to prevent fungal infections.