Microsporidiosis

Key Features

Essentials of Diagnosis

• Acute diarrhea, especially in children in developing countries

• Outbreaks of diarrhea secondary to contaminated water or food

• Prolonged diarrhea in immunocompromised persons

• Diagnosis mostly by identifying organisms in specially stained stool specimens

General Considerations

• Infection occurs mainly by ingestion of spores, but also by direct inoculation of the eyes

• May be transmitted from person to person or by contaminated drinking or swimming water or food

• Cysts can remain viable in the environment for years

Demographics

• Occurs worldwide, particularly in the tropics and in regions where hygiene is poor

• Clustering occurs in households, day care centers, and among sexual partners

Clinical Findings

Symptoms and Signs

In immunocompetent patients

• Most commonly presents as self-limited diarrhea

• Ocular infections have also been described

In immunocompromised patients

• Most commonly caused by Enterocytozoon bieneusi and Encephalitozoon intestinalis

• Chronic diarrhea, with anorexia, bloating, weight loss, and wasting

• Fever is usually not seen

• Other illnesses include

  • Biliary tract disease (AIDS cholangiopathy)

  • Genitourinary infection with cystitis

  • Kidney disease

  • Hepatitis

  • Peritonitis

  • Myositis

  • Respiratory infections including sinusitis

  • Central nervous system infections including granulomatous encephalitis

  • Disseminated infections

• Ocular infections with Encephalitozoon species cause conjunctivitis and keratitis, presenting as redness, photophobia, and loss of visual acuity

Diagnosis

Laboratory Findings

• Identification of organisms in stool, fluid, or tissue specimens using Weber chromotrope-based stain

Diagnostic Studies

• Electron microscopy is helpful for confirmation of the diagnosis and speciation

• Polymerase chain reaction and culture techniques are available but not used routinely

Treatment

• Albendazole (400 mg orally twice daily for 2–4 weeks)

  • Has activity against a number of species, but relatively poor efficacy (about 50%) against E bieneusi, the most common microsporidial cause of diarrhea in patients with AIDS

  • Used to treat gastrointestinal and other manifestations

• Fumagillin

  • Has shown benefit in clinical trials at a dose of 20 mg orally three times per day for 14 days

  • Treatment was accompanied by reversible thrombocytopenia

• For ocular microsporidiosis

  • Fumagillin solution (3 mg/mL)

  • Consider concurrent systemic therapy with albendazole

  • Adjunctive management may include corticosteroids to decrease inflammation and keratoplasty

• Antiretroviral therapy is the best means of controlling microsporidiosis in patients with AIDS

Outcome

Prevention

• Optimal means of preventing microsporidial infections are not well understood, but water purification as discussed above and body substance precautions for immunocompromised and hospitalized individuals are likely effective

References