Giardia infection occurs worldwide. Groups at high risk include infants, young children, international adoptees, travelers, immunocompromised individuals, and patients with cystic fibrosis.
Transmission of infectious Giardia cysts to humans may occur via 3 routes: waterborne, fecal-oral, or foodborne.
Giardiasis is especially common in areas with poor sanitary conditions and limited water-treatment facilities.
Symptoms of acute giardiasis include diarrhea, malaise, and abdominal cramps. Chronic giardiasis can result in significant weight loss, while acquired lactose intolerance occurs in up to 40% of patients.
Antigen and nucleic acid detection tests are more sensitive than stool microscopy.