Giardiasis causing chronic diarrhoea in suburban Copenhagen: incidence, physical growth, clinical symptoms and small intestinal abnormality.

During a six-year period, 29 children (aged 0.7-13.5 years, mean 3.3 years) suffering from chronic diarrhoea due to giardiasis were studied. The incidence of this illness was 81 per 1,000,000 children aged 0- < 7 years per year. According to growth charts, relative height and weight of the patients decreased significantly (approximately 0.5 SD) from before the onset of diarrhoea to the time of diagnosis and subsequently increased up to the end of catch-up growth. Small intestinal mucosal specimens were studied. Two patients had severe villous atrophy, 8 moderate abnormalities, 6 only light changes and 13 biopsies were normal. D-xylose or lactose malabsorption was detected in 25% of the patients. The lactose malabsorption was due to hereditary low lactase levels. None of the patients with a Danish ethnic background showed lactose malabsorption. D-xylose absorption and the relative weight loss of the patients correlated with the degree of mucosal damage. Patients with persistent diarrhoea (n = 19) were younger and had a shorter duration of diarrhoeal illness and a more significant weight reduction than those with intermittent diarrhoea (n = 10). However, the age at onset of symptoms was similar in the two groups (medians 1.3 years). Seven patients contracted the disease abroad. They all developed persistent diarrhoea and had a more severe course of the illness than those who acquired the disease in Denmark.