VIRUSES AND PARASITES AS COMMON PATHOGENS OF ACUTE INFECTIOUS DIARRHEAL DISEASES

VirusesViral infection by rotaviruses, Norwalk agent, adenovirus, and astroviruses are easily spread and frequent causes of diarrhea in children. Most cases are waterborne or food-borne, and after an incubation period of more than 12 hours, symptoms of nausea, vomiting, and watery diarrhea predominate. Bouts are self-limited, and treatment should include antidiarrheals and rehydration.
ParasitesGiardia lamblia, Entamoeba histolytica, Cryptosporidium, and Cyclospora are the most common parasites causing diarrhea in travelers, patients with acquired immunodeficiency syndrome (AIDS), and people in day care centers. Persistent diarrhea lasting longer than 2 weeks and travel to underdeveloped or mountainous regions should prompt evaluation for parasites in the appropriate patient. Giardia infection may be self-limited or chronic and is diagnosed by microscopic visualization, direct immunofluorescence, or, more commonly, enzyme-linked immunosorbent assay (ELISA). Empiric treatment may be justified in patients with persistent diarrhea without further testing. Preferred treatment is metronidazole or albendazole. Cryptosporidium parvum is transmitted fecal-orally, through contact with farm animals, food, or water, and is resistant to chlorination. Diagnosis is made by identification of oocysts in fresh stool or by ELISA. Patients with human immunodeficiency virus (HIV) infection whose CD count is less than 200 are at increased risk for chronic infection, severe dehydration, wasting, and death. In immunocompetent individuals, the disease is self-limited. Trials are currently underway to find an appropriate treatment. E. histolytica can cause a variety of illnesses, including bloody diarrhea, ulcerative colitis, and metastasis with liver abscesses and involvement of lungs, heart, and brain. Identification of cysts or trophozoites or positive ELISA findings should prompt treatment with metronidazole followed by diloxanide or paromomycin – the latter two agents for prevention of systemic invasion by remaining cysts.*71/348/5*

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