G. duodenalis, a single celled protozoa, is the most frequent cause of non-bacterial diarrhea in the United States. The Centers for Disease Control and Prevention (CDC) estimates as many as 2.5 million cases of Giardia infection occur annually in the U.S. Symptomatic individuals may experience diarrhea, abdominal cramps, dehydration, malabsorption, loss of appetite, anemia, and weight loss 1-2 weeks following the ingestion of cysts. Typically symptoms will last 1-2 weeks and infections are self-limiting. Most individuals will be completely asymptomatic. Prevalence of giardiasis in adults has been estimated to be 4-7%. Higher prevalence rates have been reported in children.
According to the Food and Drug administration, the higher prevalence of giardiasis in children versus adults suggests that many individuals have a lasting immunity following infection. Approximately 40% of patients diagnosed with giardiasis will demonstrate disaccharide (particularly lactose) intolerance that may last up to six months. Chronic cases of giardiasis may last months to years and are difficult to treat. Chronic giardiasis may lead to a malabsorption syndrome, weight loss, and general weakness and fatigue.
Giardia lives in the intestines of infected humans or animals. Contamination with Giardia from soil, food, water, or surfaces can occur from contact with feces from infected sources. Person to person transmission is common in day-care centers where diapering is done, as well as in institutions for persons with special needs. Resistance to drug treatment is common; however, Metronidazole (Flagyl) is effective. Paromomycin is the alternative for treating Giardia during pregnancy. Other therapeutic alternatives include nitazoxanide, furazolidone, and quinacrine. Natural substances include berberine, grapefruit seed extract, and quassia. Fatty foods should be avoided, as Giardia feeds on bile salts.
Giardia duodenalis (AKA intestinalis & lamblia)
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