Attempted isolation of Blastomyces dermatitidis from native shrews in northern Wisconsin, USA

The precise ecological niche of Blastomyces dermatitidis is unknown. The related dimorphic fungus, Paracoccidioides brasiliensis, has been isolated from South American ground-dwelling insectivorous armadillos. We attempted to isolate Blastomyces from shrews, North American ground-dwelling insectivores that have been shown to harbor Histoplasma capsulatum in endemic areas. Forty-seven masked shrews (Sorex cinereus) and 13 northern short-tailed shrews (Blarina brevicauda) were collected in endemic areas of northern Wisconsin and Michigan using pitfall traps. Specimens were collected between 1998 and summer 2002, stored frozen, then necropsied. Cultures of nasopharynx, lungs, liver, spleen and large and small bowel were placed on yeast extract phosphate agar with one or two drops of ammonium hydroxide. Cultures for Blastomyces were negative from all 60 shrews and two deer mice (Peromyscus maniculatus) and three southern red-backed voles (Clethrionomys gapperi), which were trapped inadvertently. Histological examination of 36 of these specimens revealed no Blastomyces yeast forms. Northern Wisconsin shrews do not appear to be carriers of B. dermatitidis.