Two Outbreaks of Blastomycosis Along Rivers in Wisconsin: Isolation ofBlastomyces dermatitidisfrom Riverbank Soil and Evidence of its Transmission Along Waterways

Abstract

Blastomycosis cannot yet be prevented or controlled, in part because the natural habitat of the causative fungus, Blastomyces dermatitidis, remains ill defined. In investigating 2 outbreaks of blastomycosis that occurred in the summer of 1985 among persons engaged in activities along rivers in contiguous central Wisconsin counties, we isolated B. dermatitidis from soil at one of the riverbanks. Blastomycosis developed in 7 (58%) of 12 residents and guests who had gathered at a pheasant farm on the Tomorrow River in early May, and in 7 (88%) of 8 boys and 1 adult who had visited a site on the Crystal River in early June. Of the 14 patients, 13 (93%) were symptomatic. Two patients visiting the sites only once became ill 23 and 78 days after exposure, respectively. We traced one outbreak to fishing from the bank of the Tomorrow River, and the other to climbing into an underground timber fort along the Crystal River. A culture of soil and organic debris from the fishing site yielded B. dermatitidis. From these and other outbreaks, and studies of endemic disease, we conclude that riverbanks can be a natural habitat of B. dermatitidis, and that the environment around waterways represents the most important site yet identified for transmission of B. dermatitidis.

Blastomycosis hospitalizations in northwestern Ontario: 2006–2015

“…This finding can be attributed to men dominating the types of labour (such as excavation or construction) common in these areas. More men than women may also prefer recreational activities near waterways that favour growth of B. dermatitidis (5). The exception was in the 50-to 59-year age group, where 59% of cases were female and 41% male.…”

“…Although blastomycosis infection occurs primarily through the inhalation of airborne spores, it can also occur, though rarely, through a puncture in the skin with infected material. Exposure to the fungal spores may increase during excavation and construction operations as well as during recreational activities that involve contact with soil near waterways as the moist and acidic soil environment is favourable to B. dermatitidis growth (2,5). Aerosolization of spores occurs more readily from dry soil that is disturbed (2).…”

Factors associated withParacoccidiodes brasiliensisinfection among permanent residents of three endemic areas in Colombia

“…The fungus microfoci was also noted to be associated with bodies of water [24]. However, many other investigations done in locations where common-source exposure was suspected proved unsuccessful in recovering the organism from soil [25].…”

Geodemographic Features of Human Blastomycosis in Eastern Wisconsin

“…3 While reports are emerging from lesser endemic portions of the state, 4,5 most epidemiologic investigations of sporadic and outbreak cases have focused on rural northern and central Wisconsin. [6][7][8][9][10][11][12][13][14][15][16][17] Despite generally lower incidence rates of blastomycosis in more urban eastern and southeastern Wisconsin counties, case numbers often meet or exceed those from their rural Wisconsin counterparts. For example, recent annual incidence rates for rural Vilas County, Wisconsin (27/100,000) 10 equate to 5.5 cases per year from this county.…”