Blastomyces dermatidis is a dimorphic fungus existing as a mold in the soil (saprophytic stage) and as a yeast in tissues (parasitic stage). It causes systemic fungal diseases called blastomycosis. It is for the first time in the year 1982 that Blastomyces dermitidis from the lungs of an insectivorous bat trapped was reported in Delhi. Histopathologically, there is a case report of blastomycosis in aged male pariah dog in India. Infection develops when spores or mycelial fragments, aerosolized from soil, are inhaled and deposited in alveoli.
Diagnosis: Smears of aspirates, and tissue impressions are stained with a Romanvsky-type (e.g. Wright’s or Giemsa) or a fungal stain (periodic acid-schiff [PAS], Gridley or Gomori methenamine silver) and examined for yeast cells. The fungus can be cultured on Sabouraud’s agar (with or without inhibitors) incubated at 25-30 °C for up to 3 weeks. Yeast form of the fungus is difficult to obtain on culture, however, the mold can be converted to yeast phase by increasing the temperature to 37 °C.Treatment: Blastomycosis responds to amphtericin B and ketoconazole or to itracnazole. Fluconazole is faily effective.