IMMUNOLOGICAL RESPONSE TO INFECTION WITH GIARDIA-LAMBLIA IN CHILDREN - EFFECT OF DIFFERENT CLINICAL SETTINGS

Infection with Giardia lamblia varies in both its severity and duratio n. A high incidence of giardiasis in immunoglobulin-deficient individu als suggests a role for the humoral immune response in resistance to G iardia infection. Levels of specific anti-Giardia antibodies were dete rmined in three populations of children infected with the parasite: in children attending a day-care centre in which strict hygiene measures were practised and in whom all Giardia infections were asymptomatic; in a rural population residing under poor hygienic conditions in close proximity to farm animals in which children with Giardia-associated d iarrhoeal episodes were studied; and in Bedouin infants followed from birth and in whom a previous study has shown that Giardia infection is almost universal by the age of 2 years. In day-care children, infecti on was accompanied by a significant increase in anti-Giardia IgM level s, compatible with an initial exposure to the parasite, In populations in which exposure to the parasite occurs at an early age and the prev alence of infestation is high, the pattern of specific antibodies to t he parasite is rather uniform and cannot differentiate between current infection and previous exposure, Thus, other immune parameters such a s salivary or urinary secretory IgA, which reflect the intestinal IgA response, should be studied in order to delineate further the humoral immune response to Giardia.