Diagnosis and Treatment
Diagnostic Tests
  • Identification of cysts in stool sample, using trichrome or iron hematoxylin staining (19).
  • More than one sample is recommended (at least 3 stool samples with two days between each), since the presence of cysts in the stool can be highly irregular, and cysts may not be present until a week after symptoms appear. (14)
  • Trophozoites break up rapidly in the stool, and should not be relied upon to measure an infection (14).
  • An Enzyme-Linked Immunosorbent Assay (ELISA) may be used to detect Giardia antigens in the stool, and is commercially available (highly sensitive). (14)
  • String Test: a patient swallows a capsule with a string attached, and when it is passed into the small intestine, trophozoites stick to the string. The string is then removed and examined for the trophozoites. (19)
  • A duodenal biopsy may also be useful to detect trophozoite presence, although trophozoites may be hard to distinguish in the sample (14)
  • Seropositivity tests are not recommended, since they cannot distinguish between current and previous infections (19).
  • A CBC (complete blood count) is not helpful, because eosinophilia is not present, and the white blood cell count should be normal. (14)
Treatment
 
  • Metronidazole (also known as Flagyl) is a first-line treatment (9)
    Dosage: Adult: 250mg per oral three times a day, for 5-7 days
                  Child: 5 mg/kg per oral three times a day, for 5-7 days (14)
    Contraindications: if patient has documented hypersensitivity, or pregnancy (there are potential risks, must outweigh risks). (14)

  • Tinidazole (Tindamax) is also a first-line treatment
    Dosage: Adult: 2 g per oral once with food (14)
    Child: >3 yrs, 50mg/kg per oral once with food (14)
    Contraindications: documented hypersensitivity, first trimester pregnancy (14)

  • Nitazoxanide (also know as Alinia) inhibits trophozoite growth by disrupting their energy metabolism, is available in liquid form for children. (14)
    Dosage: Adult: 500 mg PO bid for 3 d (14)
      Child:  <1 yr: not documented
                                                      1-4 years: 100 mg (5 mL) per oral every 12 hrs for 3 days with food
                  4-11 years: 200 mg (10 mL) per oral every 12 hrs for 3 days with food (14)
                            Contraindications: documented hypersensitivity

  • Paromomycin (Humatin) may be used to treat severe infections in pregnant women, but has worse side effects and long term use is not recommended. (14)
    Dosage: 25-30 mg/kg per oral three times a day for 7-10 days (same for children) (14)
    Contraindications: intestinal obstruction, hypersensitivity (14)

  • Furazolidone (Furoxone) is available in liquid form, although is less effective than other treatments, and children should be watched carefully for relapse (14)
    Dosage:  Adult:100 mg per oral four times a day for 7-10 days
       Child: 6 mg/kg/d per oral divided four times a day for 7-10 days (14)
    Contraindications: documented hypersensitivity

  • Also effective: albendazol and mebendazole(9)