Giardia Giardiasis is caused by Giardia intestinalis, a protozoan spread by fecal–oral transmission While humans are the primary reservoir, domesticated and wild animals can also be infected Most U.S outbreaks have been associated with contaminated drinking water, daycare facilities, and food handlers One-half to three-quarters of infections are asymptomatic Symptoms include malodorous watery, nonbloody diarrhea, flatulence, abdominal pain, and weight loss Anemia may be noted Children with humoral immunodeficiencies can develop chronic symptomatic infection The diagnosis is based on EIA or direct fluorescent antibody (DFA) assays, which have sensitivity and specificity far superior to identification of organisms in the stool Treatment is not needed for self-limited infections in normal hosts, and treatment of asymptomatic carriers is not recommended unless they live in the home with an immunocompromised person For patients requiring treatment, metronidazole (5 mg/kg every hours [maximum: 250 mg/dose for to days]), tinidazole (single dose, licensed for children years of age and older: 50 mg/kg [maximum: g]), or nitazoxanide (3-day course for children year of age and older: to years: 100 mg twice daily, to 11 years: 200 mg twice daily, ≥12 years: 500 mg twice daily) are options Standard and contact precautions should be used for the incontinent child Cryptosporidium Cryptosporidiosis is caused by C parvum and C hominis, protozoal species spread by fecal–oral transmission Humans, cattle, and other animals are reservoir species In the United States, almost 8,000 cases occur annually, so a travel history is not a prerequisite for infection Risk factors include swallowing contaminated water (including at hotel swimming pools), hiking and drinking unfiltered water, daycare attendees, workers, and the families of children who attend day care, and travelers Asymptomatic infection can be seen Most patients will develop low-grade fever, watery, nonbloody diarrhea with crampy abdominal pain, vomiting, and weight loss Symptoms last to weeks, although more severe and chronic symptoms can be seen in HIV-infected patients and other immunocompromised hosts In addition, immunocompromised children can develop extraintestinal manifestations: biliary tract and pneumonitis DFA and EIAs are more sensitive than detection of oocytes in stool Self-limited illness in immunocompetent hosts usually does not require treatment Nitazoxanide is approved for children year of age and older (3-day course for children year of age and older: to years: 100 mg twice