Giardiasis (caused by the protozoan Giardia lamblia) is the most prevalent protozoal infection of the human intestine and is one of the most common causative agents of epidemic and endemic diarrhoea in the world. Infection is acquired by ingestion of infectious G. lamblia cysts, either in contaminated water or food or via direct person-to-person contact.
Most infected subjects are asymptomatic, and most infections are self-limited. However, chronic infections, marked by chronic diarrhoea/steatorrhoea and malabsorption, can occur and can last for weeks to months. The symptoms may include acute watery diarrhoea, chronic diarrhoea with malabsorption and weight loss, and abdominal cramping. Abdominal cramping, bloating, and flatulence occur in 70-75% of symptomatic patients.
The diagnosis is made by stool examination and ideally, 3 specimens from different days should be examined because of potential variations in faecal excretion of cysts. No special diet is required. As many patients have symptoms of lactose intolerance (cramping, bloating, diarrhoea), try and maintain a lactose-free diet for several months. Treatment is antibiotic therapy - metronidazole (250 mg orally three times a day for 5 days) or albendazole (400 mg orally four times a day for 3 days).