Blastomycosis is a chronic skin disorder caused by opportunistic Blastomyces dermatitis (1). B. dermatitis is a dimorphic fungus that exists in the mycelial and the yeast phase. Since most Blastomyces infections occur via inhalation of conidia, it seems soil is a niche for this fungus (2). Cases of Blastomycosis have been reported from all parts of the world (3). In the United States, the fungus is epidemic to the Ohio and Mississippi River areas. The Blastomycosis is very rare compared to Histoplasmosis (4).

Infection with B. dermatitis produces a wide spectrum of illness in humans and canines. Isolated pulmonary Blastomycosis is the most frequent clinical manifestation of the disease.

One of the impediments to serodiagnosis of Blastomycosis has been the lack of suitable antigen. The "A" antigen which is a culture filtrate of Blastomyces yeast cells provides a useful tool for serodiagnosis of Blastomycosis. In one study (5) antigen "A" of B. dermatitis was used in an EIA. Study showed (6) that EIA is the most sensitive serological test for Blastomycosis. EIA assays detect 77% of definite and probable cases of Blastomycosis cases as compared to 27% and 8% for immunodiffusion and complement-fixation tests, respectively. The Micro Detect "BLASTOMYCES DETECT IgM" is an EIA assay which uses the cell-filtrate of B. dermatitis as the antigen for detecting specific serum IgM to B. dermatitis in human sera.