Blastocystis hominis infection

CASES/YEAR
16,000 (US); 300,000 (Global)
CATEGORY
Gastroenteritis--Noninflammatory
AGENT TYPE
Protozoa
OTHER NAMES
Blastocystosis
ACUITY
Subacute/Chronic
INCUBATION
INITIAL SYMPTOMS
Diarrhea
PRECAUTIONS
COMMENTS
Blastocystis hominis commonly inhabits the colon of humans. Its pathogenicity is not well understood. Fecal-oral spread by the cyst form is suspected. Some patients have diarrhea, abdominal cramping, nausea & vomiting, and malaise. Treatment of asymptomatic carriers is not warranted. [Guerrant, p. 621-2] The prevalence of infection is higher in developing countries (30% to 50%) than in developed countries (1.5% to 10%). [PPID, 3427] The pathogenicity of B. hominis is debated. [Cecil, p. 2116t]
DIAGNOSTIC
Identification of cysts in trichrome stained stool sample; Serology is not useful for diagnosis. PCR (sensitive and specific) is becoming widely available. [PPID, p. 3427]
SCOPE
Global
SIGNS & SYMPTOMS
  • >fatigue, weakness
  • >fever
  • G abdominal pain
  • G diarrhea
  • G nausea, vomiting
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Ingestion
SOURCE
Person-to-Person, Human Fecal-Oral, Waterborne (Ingesting, Inhaling, or Swimming)
RESERVOIR
Human
RISK FACTORS
  • Ingest infectious agents in food/water
  • Travel to endemic area
TREATMENT
Asymptomatic infections do not need treatment. Rule out other causes before treating "symptomatic" infections. [PPID, p. 3427] "If diarrheal symptoms associated with Blastocystis are prominent, either metronidazole (750 mg thrice daily for 10 days) or TMP-SMX (160 mg/800 mg twice daily for 7 days) can be used." [Harrison ID, p. 1123]
DRUG LINK
REFERENCES FOR CASES/YEAR
1. (US) No data found; Assume same cases/yr as Cyclospora;
2. (Global) "It seems not to cause any disease in most cases of isolation." [Gorbach, p. 421] No data found; Assume same rate as Cyclospora;