Nejm 1978;298:319

Cause:Giardia lamblia

Pathophys:Malabsorption due to mechanical obstruction of duodenum, hence fat absorption is especially hard hit

Encysted form excreted in feces, ingested by new host, resides in duodenum. Animal reservoirs: beaver, dog, muskrat, perhaps deer

Occurs in areas of poor sanitation with raw rural surface (not ground) water; gay males; Southeast Asian refugees. Associated with globulin deficiencies, especially of IgA; achlorhydria, nodular lymphoid hyperplasia

Sx:

Loose, watery stools (93%), malaise (80%), bloating and cramps (75%), fatigue, weight loss (73%); true diarrhea in only 30%

"Traveler's diarrhea," which often doesn't start until return from a trip, ie, delayed onset

10-d incubation period, 10+-wk duration

Malabsorption, upper gi bleed rarely

Lab:

Bact: Stool O⁺P, 70% false neg; 2 "eyed" (nuclei) flagellated trophozoite, or 4 nucleated cyst. Examination of duodenal aspirate or small bowel bx (<10% false neg)

Serol:Giardia antigen in stool

Rx:

Prevent by avoiding sewage contamination of water supplies; filtration; iodine as 2% solution, 0.4 cc/L of water; or heating to 70°C (158°F) × 10 min (Am J Pub Hlth 1989;79:1633). Chlorination probably inadequate even at 8 mg Cl^–/L × 10 min

of active disease:

• Metronidazole (Flagyl), 1st, 250 mg or 5 mg/kg tid × 5-7 d; or tinidazole, or alternatively
• Furazolidone 100 mg or 1.25 mg/kg qid × 5 d; no carcinogenicity
• Nitazoxanide (Alina) (Med Let 2003;45:20) 500 mg po bid (100-200 mg bid in children)