Blastocystis hominis

Background

Epidemiology

• Worldwide, but varies by subtype
  • Subtype 3 most common worldwide in human
  • Subtype 4 is in Europe
• Prevalence higher in developing than developed countries

Clinical Presentation

• Unclear if it causes a clinical syndrome; may be strain-dependent
• Has been implicated in acute diarrhea, chronic diarrhea, bloating, flatulence, abdominal cramping, and fatigue, as well as irritable bowel syndrome

Diagnosis

• Stool microscopy with trichrome stain
• In vitro cell culture
• PCR is standard

Management

• Eliminate all other causes of symptoms
• If still symptomatic, can consider treatment
  • Nitazoxanide 500 mg po bid for 3 days
  • Can also try: metronidazole 750 mg po tid for 10 days, trimethoprim-sulfamethoxazole DS 1 tab po bid for 7 days, and iodoquinol 650 mg po tid for 20 days
  • Unclear which, if any, is helpful