Parasites (Intestinal)

NOTE: Stool for Ova & Parasites (O&Ps) requires 3 specimens on separate days.

Giardia (most common parasite)
  • Best test: fresh stool for Giardia Antigen
  • Risks: Travel (3rd World, Russia), wilderness hiking, MSM
Ameba
  • Pathogen: Entamoeba histolitica (risk: 3rd World travel)
  • Non-Pathogen: E. dispar, E. moshkovskii (common among gay men)
  • Distinguish by sending fresh stool for Antigen Detection
  • Serology for E. histolitica useful if negative
  • E. histolitica causes dysentery & liver abscesses
Trichuris trichiura (“whipworm”)
  • Rare in U.S. (maybe common in rural Southeast)
  • Risk: 3rd World travel
  • Suspect if eosinophilia
Strongyloides
  • Risk: 3rd World travel.  Can persist for decades
  • Suspect if eosinophilia
  • O&P’s poor; order ELISA serology for immunocompetent persons
  • Very hard Dx in immunocompromised
Blastocystis spp. (a.k.a. B. hominis)
  • Probably not pathogenic
  • Thus, no documented Tx
  • Suggestion: Tx for Giardia w/ low-dose Metronidazole (250 mg TID x5d)

See posting Chronic Diarrhea.