Giardial Enteritis

Giardial enteritis is infection of the small intestine by Giardia lamblia (G. duodenalis), acquired by ingestion of cysts in contaminated water or food, or person to person. It is common among children in Kenya, in nurseries, in people with HIV, travellers and hypogammaglobulinaemia.

• Cysts survive chlorination and cold water.
• Infection causes epithelial damage, villous atrophy and malabsorption.

Incubation 1 to 2 weeks, then watery or greasy foul smelling diarrhoea, bloating, flatulence, cramps, nausea, belching with sulfurous taste, and weight loss; fever is uncommon.

• Chronic infection: steatorrhoea, lactose intolerance, failure to thrive, vitamin deficiency, fatigue; many carriers are asymptomatic.
• Differential diagnosis: cryptosporidiosis, cyclosporiasis, isosporiasis, bacterial gastroenteritis, coeliac disease, tropical sprue, lactose intolerance, irritable bowel syndrome, inflammatory bowel disease, small bowel bacterial overgrowth, HIV enteropathy, chronic pancreatitis.
• Complications: dehydration, malabsorption, weight loss, growth retardation in children, post infectious irritable bowel syndrome, reactive arthritis, lactose intolerance, chronic infection in immunodeficiency.

Stool tests or small bowel sampling.

• Stool microscopy for cysts and trophozoites (three samples on separate days, sensitivity 50 to 70 percent for one sample); stool antigen test or PCR (more sensitive).
• Duodenal aspirate or biopsy when stool tests are repeatedly negative but suspicion is high.
• Full blood count, albumin, vitamin B12, HIV test, immunoglobulins in refractory disease, faecal fat.

Nitroimidazole therapy with rehydration.

• Supportive: oral rehydration, continued feeding, lactose restriction for a few weeks, hand washing, boiled water, hygiene in nurseries, exclusion from childcare until diarrhoea settles, treat household carriers.
• Pharmacological: tinidazole 2 g single oral dose (children 50 mg/kg, maximum 2 g); or metronidazole 250 mg three times daily for 5 to 7 days (children 15 mg/kg/day in 3 doses for 5 days); or secnidazole 2 g single dose (children 30 mg/kg); or nitazoxanide 500 mg twice daily for 3 days (1 to 3 years 100 mg twice daily; 4 to 11 years 200 mg twice daily); or albendazole 400 mg daily for 5 days. Refractory or relapsed: repeat course, or metronidazole 500 mg three times daily with albendazole 400 mg daily for 10 days. Pregnancy first trimester: paromomycin 500 mg three times daily for 7 days. Zinc 20 mg daily for 10 to 14 days in children.
• Procedures: endoscopy with duodenal biopsy for diagnostic uncertainty.
• Special groups: pregnancy, paromomycin in the first trimester and nitroimidazoles after; children, weight based dosing and nutrition; HIV, longer treatment and antiretroviral therapy to restore immunity; immunodeficiency, prolonged courses.
• Red flags: severe dehydration, profound weight loss, steatorrhoea unresponsive to treatment, bloody stool (consider other cause), fever, failure to thrive.
• Follow-up: stool re-examination at 2 weeks only if symptoms persist; test household contacts if recurrent; nutritional recovery.