Epidemiology of Systemic Mycoses
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p745-746
2025-12-01
54
Blastomyces dermatitidis
B. dermatitidis commonly produces a chronic infection that contains a mixture of suppurative and granulomatous inflammation. The disease (blastomycosis) is most commonly found in North America and extends south ward from Canada to the Mississippi, Ohio, and Missouri river valleys, Mexico, and Central America. Some isolated cases have also been reported from Africa. The largest numbers of cases occur in the Mississippi, Ohio, and Missouri river valley regions. The exact ecologic niche for this organism in nature has not been determined; however, patients with blastomycosis often have a history of exposure to soil or wood. Several outbreaks have been reported and have been related to a common exposure. Blastomycosis is more common in men than in women and seems to be associated with outdoor occupations or activities. The disease also occurs in dogs.
Coccidioides immitis
C. immitis is found primarily in the desert portion of the southwestern United States and in the semiarid regions of Mexico and Central and South America. Although the geographic distribution of the organism is well defined, infection may be seen in any part of the world because of the ease of travel. The infection (coccidioidomycosis) is acquired by inhalation of the infective arthroconidia of C. immitis.
Histoplasma capsulatum
Outbreaks of histoplasmosis have been associated with activities that disperse aerosolized conidia or small hyphal
fragments. Infection is acquired through inhalation of these infective structures from the environment. The severity of the disease is generally related directly to the inoculum size and the immunologic status of the host. Numerous cases of histoplasmosis have been reported in people who clean out an old chicken coop or barn that has been undisturbed for long periods and in individuals who work in or clean areas that have served as roosting places for starlings and similar birds. Spelunkers (i.e., cave explorers) are commonly exposed to the organism when it is aerosolized from bat guano in caves. An estimated 500,000 people are infected with H. capsulatum annually. The history of exposure often is impossible to document, even though histoplasmosis is perhaps one of the most common systemic fungal infections seen in the Midwest and South in the United States, including areas along the Mississippi River, the Ohio River valley, and the Appalachian Mountains.
Paracoccidioides brasiliensis
Infection caused by P. brasiliensis is most commonly found in South America, with the highest prevalences in Brazil, Venezuela, and Colombia. It also has been seen in many other areas, including Mexico, Central America, and Africa. Occasional imported cases are seen in the United States and Europe. The exact mechanism by which para coccidioidomycosis is acquired is unclear; however, some speculate that it has a pulmonary origin and that it is acquired by inhalation of the organism from the environment. Because mucosal lesions are an integral part of the disease process, it also is speculated that the infection may be acquired through trauma to the oropharynx caused by vegetation commonly chewed by some residents of the endemic areas. The specific ecologic niche of the organism in nature is not known.
Penicillium marneffei
P. marneffei is an emerging dimorphic pathogenic fungus endemic to Southeast Asia, particularly the Guangxi Zhuang Autonomous Region of the People’s Republic of China. P. marneffei has been associated with the bamboo rat (Rhizomys pruinosus) and the Vietnamese bamboo rat (Rhizomys sinensis).
Sporothrix schenckii
S. schenckii has a worldwide distribution, and its natural habitat is living or dead vegetation. Humans acquire the infection (sporotrichosis) through trauma (thorns, splinters), usually to the hand, arm, or leg. The infection is an occupational hazard for farmers, nursery workers, gardeners, florists, and miners; it is commonly known as “rose gardener’s disease.” Pulmonary sporotrichosis rarely occurs as a result of inhalation of spores.
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