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Info


A. Propertiesnavigator

  1. Flagellated (4 pairs) protozoan
  2. Lives in water; transmitted by fecal-oral route
  3. Trophozoite 20x15µm with 2 nucleoli (killed in stomach)
  4. "Tennis racquet" shape
  5. Cyst is 12µm and is the infective form (can survive in stomach)
  6. Most commonly identified intestinal parasite in USA
  7. Infective dose is as low as 10-20 cysts per persons

B. Symptomsnavigator

  1. Diarrhea, Non-Bloody (80%) and Steatorrhea (70%)
  2. Abdominal pain and/or distension (70%)
  3. Lactose Intolerance with Flatulence (70%)
  4. Abdominal cramps (60%)
  5. Malaise (85%)
  6. Nausea (70%)
  7. Anorexia (65%)
  8. Weight Loss (60%)

C. Pathophysiologynavigator

  1. Mucosal competition in small intestine
  2. Bile deconjugation causes fat malabsorption
  3. Lactose intolerance due to lactase destruction
  4. Competition for Vitamin B12 and Folate

D. Diagnosisnavigator

  1. History consistent with diagnosis
  2. Stool examination for ova and parasites
  3. Detection of Giardia Antigen in stool by IFA or ELISA
  4. Duodenal Sampling
    1. String Test
    2. Duodenal Aspiration
    3. Duodenal Biopsy
  5. Response to empiric therapy

E. Therapy [2] navigator

  1. Metronidazole (Flagyl®)
    1. 250mg po tid for 5-7 days for adults
    2. 5mg/kg po tid for 7 days for children
    3. 7% of patients have moderate to severe side effects
  2. Tinidazole (Tindamax®) [3]
    1. 2gm x 1 dose
    2. Generally better tolerated than metronidazole
  3. Quinacrine
    1. 100mg po tid for 5-7 days for adults
    2. 2mg/kg tid for 7 days for children
    3. 23% side effects
  4. Nitazoxanide (Alinia®)
    1. Dose (Giardiasis, HIV-) age 12-47 months: 100mg q12 hours x 3 days
    2. Dose (Giardiasis, HIV-) age 4-11 years: 200mg q 12 hours x 3 days
    3. Very well tolerated; some abdominal pain, diarrhea, vomiting but similar to placebo rates
  5. Pregnancy
    1. Paromomycin (Humatin®) may be used for treatment
    2. 25-30mg/kg per day in 3 divided doses
    3. Therapy for 5-10 days
  6. Examine household contacts and sexual partner

References navigator

  1. Hill DR. 1993. Infect Dis Clin North Amer. 7:503 abstract
  2. Nitazoxanide. 2003. Med Let. 45(1154):29 abstract
  3. Tinidazole. 2004. Med Let. 46(1190):70 abstract