- Giardiasis is a common protozoan infection with clinical manifestations in children ranging from asymptomatic carriage to persistent diarrhoea with malabsorption. It can lead to growth and developmental retardation. The study evaluated risk factors for the initial symptomatic giardiasis (SG) episode among Arab-Bedouin children in Israel. A community-based, prospective cohort study was conducted in Rahat, a Bedouin township in southern Israel. Infants (n=238) were followed by weekly visits from birth to age 18 months. Giardia infection was identified by antigen detection in faecal specimens. Approximately 26% of children experienced one or more SG episode. Mean (SD) age for first SG episode was 12.3 (3.3) months, with 95% of episodes occurring in children >6 months of age. Risk for the first SG in children >6 months of age was associated with it being spring or summer [odds ratio (OR) 6.16, p<0.001], exposure to livestock (OR 4.89, p=0.002) and prior infection with entero-aggregative Escherichia coli (EAEC) (OR 1.12 for each additional percentage in stool prevalence, p=0.02). Weight-for-age Z-scores at age 6 months were inversely related to SG risk (OR 0.62 for each unit increase in Z-score, p=0.029). Giardiasis is an important cause of diarrhoea in Bedouin children. Increased risk of SG in spring/summer might be linked to environmental conditions or seasonal dietary practices which increase virulence or transmission. SG in those exposed to livestock suggests that there are zoonotic risk factors or that hygiene is a causal factor. The association between EAEC infection and SG warrants further investigation.