Background: Our previous publications on the epidemiology of blastomycosis suggested that the etiologic organism, Blastomyces dermatitidis, may be acquired at home, however this view was challenged in an editorial.
Methods: 1) Field study of 2 properties that preliminarily suggested disease acquisition in the home. Owner interviews, site visits and environmental cultures using our in-vitro technique were used. 2) An address registry of human and dog blastomycosis cases was constructed from extensions of our previously published case series. 3) Literature review.
Results: 1) Blastomycosis occurred in a dog (December, 1998) and then a cat confined to its home (September, 1999), from a household in urban Manitowoc County, WI; and additionally in a house-confined cat (July, 1998) at a home in Milwaukee, WI. Interviews implicated the basement and the attic or basement, respectively, as the most likely source of infection at these homes. Environmental cultures were negative for Blastomyces. Of the 229 domiciles in the registry, a minimum of 27 (12%) were associated with more than one blastomycosis case, 10 sites with more than two and 7 with more than three. In 4 domiciles, repeat cases occurred in different families. Most cases were separated by 1 year or more (range: 3 weeks to 7 years). Recent case series reveal a minority of outdoor activities and occupations among humans with blastomycosis. The organism has been isolated from an inhabited yard and from a house being razed.
Conclusions: There appears to be growing evidence that blastomycosis may be acquired at home, and that B. dermatitidis may be relatively persistent on certain properties.