Which fungus is endemic to the Mississippi and Ohio River valleys and is caused by the inhalation of bird and bat droppings?

• A. Aspergillus fumigatus
• B. Histoplasma capsulatum
• C. Cryptococcus neoformans
• D. Coccidioides immitis

Answer: (B)

Histoplasma capsulatum is the organism described. It thrives in soil enriched with bird and bat droppings, and in the Mississippi and Ohio River valleys this exposure is especially common. Inhaled microconidia from contaminated soil reach the lungs and convert to the yeast form inside macrophages, causing histoplasmosis, which can range from mild respiratory symptoms to more severe disease. This regional distribution and the link to bird and bat droppings distinguish it from the other fungi: Aspergillus fumigatus is a widespread mold with different clinical patterns; Cryptococcus neoformans is often linked to pigeon droppings and meningitis in immunocompromised patients; Coccidioides immitis is endemic to the southwestern deserts.