Coccidioidomycosis

Description

Coccidioidomycosis is an endemic systemic mycosis resulting in both asymptomatic and life-threatening disseminated infections.

Epidemiology

• Coccidioides spp. are dimorphic fungi that live in the soil.
• Endemic to the southwestern United States (southern California, Arizona, western and southern Texas, New Mexico), northern Mexico, and parts of South and Central America
• Infection is acquired from exposure to aerosolized spores (arthroconidia) usually during recreational or occupational activities; clusters of cases may involve dust storms and earthquakes.
• The average incubation period is 10 to 16 days (range 1 to 4 weeks) for primary infection.
• There is no person-to-person spread except in rare instances of draining lesions or donor derived transmission through organ donation.
• 60% of acute infections are subclinical (asymptomatic).

Risk Factors

• The course of illness is highly variable and depend on host immune response and amount of exposure.
• Risk factors for disseminated infection:
  • Immunosuppression (especially organ transplant recipients, those receiving immunosuppressive therapies and immunomodulators, and those with HIV infection)
  • Male gender (adult)
  • Neonates, infants, and the elderly
  • Filipino, African American, Native American, Hispanic ethnicity
  • Pregnancy
• Risk of dissemination is less in children than in adults.

General Prevention

• No special isolation or precautions for the hospitalized patient
• Contaminated dressings from skin lesions should be handled and discarded with care.
• Inhalation of aerosolized spores from culture can be hazardous to laboratory personnel.
• Preventive efforts are aimed at dust control and trials to eliminate organisms from soil.
• Immunocompromised people should be counseled to avoid activities that may expose them to aerosolized spores in endemic areas.

Pathophysiology

• Spores (arthroconidia) are the infectious forms of Coccidioides organisms; they are released from the mold and propagate the mold in the soil.
• Inhalation of arthroconidia from disturbed, arid soil is the major route of infection.
• In tissues, arthroconidia enlarge to form spherules. Mature spherules release endospores that propagate in the host and continue the tissue cycle.
• Primary infection occurs in the lungs.
• Most patients have infection limited to a localized area of lung and hilar lymph nodes after mounting an intense inflammatory response with granuloma formation.
• Extrapulmonary dissemination occurs via lymphatic or hematologic spread and usually involves the skin, bones and joints, and central nervous system but can spread to virtually any organ system.

Etiology

• Coccidioides immitis and Coccidioides posadasii are the etiologic agents of coccidioidomycosis.
• Asymptomatic infection is the most common outcome, occurring in 60% of infected individuals.
• Primary pulmonary infection accounts for most symptomatic cases; nonspecific illness most common feature (cough, malaise, chest pain, fever); self-limited in most cases; may be accompanied by reactive rashes such as erythema multiforme or erythema nodosum
• Disseminated disease occurs in <1% of infected individuals and may manifest with
  • Osteomyelitis:
    • Subacute or chronic and frequently involves more than one bone (40%)
    • Common sites are the hands, feet, ribs, skull, and vertebrae.
  • Meningitis:
    • Develops within 6 months of initial infection
    • Hydrocephalus is a common complication.
    • Central nervous system vasculitis and intracerebral abscesses are rare.
  • Cutaneous disease:
    • Papules or pustular lesions that ulcerate are most common.
    • Most commonly seen on the face but can occur anywhere
    • Regional adenitis is common.