as working with wood or plant material in forested or riparian areas, involvement in forestry in highly endemic areas, excavation, fishing and possibly gardening and trapping. urban infections there is also a developing profile of urban and other domestic blastomycosis cases, beginning with an outbreak tentatively attributed to construction dust in westmont, illinois. the city of rockford, illinois, was also documented as a hyperendemic area based on incidence rates as high as 6.67 per 100,000 population for some areas of the city. though proximity to open watersheds was linked to incidence in some areas, suggesting that outdoor activity within the city may be connected to many cases, there is also an increasing body of evidence that even the interiors of buildings may be risk areas. an early case concerned a prisoner who was confined to prison during the whole of his likely blastomycotic incubation period. an epidemiological survey found that although many patients who contracted blastomycosis had engaged in fishing, hunting, gardening, outdoor work and excavation, the most strongly linked association in patients was living or visiting near waterways. based on a similar finding in a louisiana study, it has been suggested that place of residence might be the most important single factor in blastomycosis epidemiology in north central wisconsin. follow-up epidemiological and case studies indicated that clusters of cases were often associated with particular domiciles, often spread out over a period of years, and that there were uncommon but regularly occurring cases in which pets kept mostly or entirely indoors, in particular cats, contracted blastomycosis. the occurrence of blastomycosis, then, is an issue strongly linked to housing and domestic circumstances. seasonal trends seasonality and weather also appear to be linked to contraction of blastomycosis. many studies have suggested an association between blastomycosis contraction and cool to moderately warm, moist periods of the spring and autumn or, in relatively warm winter areas. however, the entire summer or a known summer exposure date is included in the association in some studies. occasional studies fail to detect a seasonal link. in terms of weather, both unusually dry weather and unusually moist weather have been cited. the seemingly contradictory data can most likely be reconciled by proposing that b. dermatitidis prospers in its natural habitats in times of moisture and moderate warmth, but that inoculum formed during these periods remains alive for some time and can be released into the air by subsequent dust formation under dry conditions. indeed, dust per se or construction potentially linked to dust has been associated with several outbreaks the data, then, tend to link blastomycosis to all weather, climate and atmospheric conditions except freezing weather, periods of snow cover, and extended periods of hot, dry summer weather in which soil is not agitated. gender bias sex is another factor inconstantly linked to contraction of blastomycosis: though many studies show more men than women affected, some show no sex-related bias. as mentioned above, most cases are in middle aged adults, but all age groups are affected, and cases in children are not uncommon. ethnic populations ethnic group or race is frequently investigated in epidemiological studies of blastomycosis, but is potentially confounded by differences in residence and in quality and accessibility of medical care, factors that have not been stringently controlled for to date. in the united states, some studies show a disproportionately high incidence and/or mortality rate for blastomycosis among black people. in canada, some studies, but not others, indicate that first nations people have a disproportionately high incidence of blastomycosis. incidence in first nations children may be unusually high. the canadian data in some areas may be confounded or explained by the tendency to establish indigenous communities in wooded, riparian, northern areas corresponding to the core habitat of b. dermatitidis, often with known b. dermatitidis habitats such as woodpiles and beaver constructions in the near vicinity. communicability blastomycosis is not considered contagious, either among humans or between animals and humans. however, there are a very small number of cases of human-to-human transmission of b. dermatitidis related to dermal contact or sexual transmission of disseminated blastomycosis of the genital tract among spouses. history thomas caspar gilchrist, first describer of blastomycosis and blastomyces dermatitidis. the organisms causing blastomycosis have existed for millions of years. the pathogenic group of onygenalean fungi that give rise to conditions including blastomycosis and histoplasmosis emerged approximately 150 million years ago. the most closely related blastomycosis-causing fungi, blastomyces dermatitidis and blastomyces gilchristii, diverged during the pleistocene, approximately 1.9 million years ago. at the koster site in illinois, evidence pointing to possible blastomycosis infections among late woodland native americans has been identified. at that site, dr. jane buikstra found evidence for what may have been an epidemic of a serious spinal disease in adolescents and young adults. several of the skeletons showed lesions in the spinal vertebrae in the lower back. there are two modern diseases that produce lesions in the bone similar to the ones dr. buikstra found in these prehistoric specimens: spinal tb and blastomycosis. the bony lesions in these two diseases are practically identical. blastomycosis seems more probable as these young people in late woodland and mississippian times may have been affected because they were spending more time cultivating plants than their middle woodland predecessors had done. if true, it would be another severe penalty late woodland people had to pay as they shifted to agriculture as a way of life, and it would be a contributing factor to shortening their lifespans compared to those of the middle woodland people. blastomycosis was first described by thomas caspar gilchrist in 1894, as a skin disease. because of this, blastomycosis is sometimes called "gilchrist's disease". gilchrist initially identified the cause of the disease as a protozoan, but later correctly identified it as a fungus. in 1898 he and william royal stokes published the first description of blastomyces dermatitidis. gilchrist referred to the disease as "blastomycetic dermatitis". the systemic spread of blastomycosis was first described in 1902, in a case that had been misdiagnosed as a combination of tuberculosis and a blastomycosis skin infection. in 1907, the dimorphic nature of the blastomyces fungus was first identified. in 1912, the first case of canine blastomycosis was reported. prior to the 1930s, blastomycosis was not clearly distinguished from similar fungal conditions. a paper by rhoda williams benham in 1934 distinguished the causative agent of blastomycosis from cryptococcosis and coccidioidomycosis. in the early 1950s, blastomycosis was first determined to be a primarily respiratory disease, with most skin lesions caused by systemic spread from an initial lung infection. in 1952, the first documented case outside north or central america, in tunisia, was reported. the 1950s also saw the first introduction of antifungal drugs including amphotericin b. before 1950, the fatality rate for disseminated blastomycosis was 92%, and treatment options were limited to iodide compounds, radiation therapy, and surgery. the first azole antifungal drug, ketoconazole, was developed in the 1970s and approved in the united states in 1981. prior to 2013, the only species known to cause blastomycosis was b. dermatitidis. since that time, genomic analysis has identified multiple other blastomyces species causing blastomycosis, including b. gilchristii (2013), b. helicus (reassigned from the genus emmonsia in 2017), b. percursus (2017), and b. emzantsi (2020). the largest-ever blastomycosis outbreak in united states history occurred at an escanaba, michigan, paper mill in 2023. as of april 2023, one person had died and almost a hundred more had fallen ill. other animals the bluetick coonhound is among the dog breeds most at risk from blastomycosis. blastomycosis affects a broad range of mammals. as with humans, most animals that become infected were formerly healthy and immunocompetent. dogs are frequently affected; blastomycosis is eight to ten times more common in dogs than in humans. sporting and hound breeds are at the greatest risk. cats and horses can also be infected. cats with feline immunodeficiency virus are particularly at risk. however, the overall risk of blastomycosis in cats is 28 to 100 times lower than in dogs. cases of blastomycosis have also been reported in captive lions and tigers, in a wild north american black bear, and in marine mammals such as the atlantic bottlenose dolphin. the nonspecific symptoms that make blastomycosis difficult to diagnose in humans also complicate veterinary diagnosis. cats in particular are often only diagnosed after death. dogs and humans frequently acquire blastomycosis from the same exposure event. in most such cases, the infection in the dog becomes apparent before the human infection. this may be due to a shortened incubation period, caused by the dog inhaling larger quantities of blastomyces spores than the human. in veterinary care, blastomycosis is typically treated with itraconazole. 70% of treated dogs respond to medication and recover. in dogs as in humans, the prognosis for blastomycosis depends on the severity of the symptoms. additional images granuloma with early suppuration. fungal organisms difficult to recognize at this low magnification. large yeast-like fungi seen within giant cells at arrows. large yeast-like fungi seen within giant cells at arrows. budding yeasts in cytoplasm of giant cells at arrows. broad-based budding and double contoured cell wall seen in the giant cell in the center is characteristic of blastomyces dermatitidis. nodular skin lesions of blastomycosis, one of which is a bullous lesion on top of a nodule.