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Characteristics of Histoplasma capsulatum
Thermal dimorphic fungus
Droppings provide growth factors
Endemic regions include Ohio, Mississippi River Valleys
Aerosolized microconidia are inhaled when soil or other material disturbed
Hyperendemic foci: bird roosts, systemic fungi, Histoplasma capsulatum, Histoplasmosis old insulation, dead trees, caves barns, renovation of old structures
No person-to-person transmission
Pathology
Immunocompetent host: systemic fungi, Histoplasma capsulatum, Histoplasmosis granulomatous inflammation with giant cells, yeast-like fungi may be seen in reticuloendothelial system, lung
Immunosuppressed host: poor granuloma formation, yeast laden histiocytes can be seen in the bone marrow
Epidemiology/Transmission
Aerosolized microconidia (often urban)
Endemic regions Mississippi, Ohio River valleys
Hyperendemic foci/activities: windy, dry soil; renovation or cleaning basements, attics, fireplaces, old insulation; digging in bird roosts; caving; playing in barns, hollow trees; cutting dead wood
No person-to-person transmission
Clinical Manifestations
Asymptomatic (unrecognized) in 99% of lightly exposed
Clinical disease in 50% of heavily exposed persons
Indications and Drugs for Therapy of Cocci
Asymptomatic - no therapy
Uncomplicated primary pulmonary infection
Fluconazole is well tolerated and may decrease risk of complications (which occur in only 0.5% of infections)
Acute life-threatening, e.g., progressive pulmonary or disseminated infection; use Amphotericin B
Non-life-threatening infections, use fluconazole
CNS
Fluconazole is used rather than amphotericin; therapy is continued for life; amphotericin B IV and via 0mmay reservoir for failures
Manifestations depend on integrity of cell-mediated immune function. Humoral immunity is not protective
Symptoms
1. Immunocompetent host
a. Fever may be present, undifferentiated flu-like symptoms, cough, chest pain, hilar lymphadenopathy
b. Large inoculum; persistent fever, weight loss, nodular infiltrate, lymphadenopathy; cough can be progressive.
2. Immunodeficient host and otherwise normal infant:
a. Prolonged fever, weight loss,
c. Directly proportional to disease severity, especially dissemination
d. Negative result does not exclude infection
5. Nonspecific tests
a. CXR - hilar adenopathy, peripheral, soft infiltrates; calcification may be present; diffuse nodular infiltrates in intense exposure. CXR can be negative in disseminated infection.
b. ESR is elevated
c. CBC is usually normal, but mild anemia may occur. Pancytopenia. DIC may rarely occur, suggesting disseminated infection
d. Skin test has no role in diagnosis. It is an epidemiologic tool
Treatment
1. Amphotericin B for
2. Itraconazole is recommended for less severe manifestations and following induction with amphotericin B.
3. Lifelong suppression is needed for AIDS patients only (itraconazole, amphotericin B)