Parasite-specific plasma immunoglobulins have been used to indicate the pre
sence of Giardia intestinalis infection in 60 infants living in a rural are
a of The Gambia. Infants were studied longitudinally between 2 and 8 mo of
age, The median age for first exposure to G. intestinalis was between 3 and
4 mo, and by 8 mo all but 3 infants (95%) showed a positive titer on at le
ast one occasion. Raised Giardia-specific IgM titers were associated with r
educed weight gain in the 2 wk preceding a positive titer, but catch-up gro
wth occurred in the following 2 wk. IgM antibody titers were also positivel
y associated with intestinal permeability (lactulose/mannitol ratio), urina
ry lactose excretion, plasma concentrations of alpha(1)-antichymotrypsin an
d total IgM, IgA and IgG immunoglobulins. However, infant growth over the w
hole 6-mo period (i.e., between 2 and 8 mo of age) was not related to mean
Giardia-specific antibody titers, nor the time of first exposure to the par
asite. The data suggest that giardiasis in these very young breast-fed chil
dren occurs as a mild, acute disease, and its presence could not explain th
e marked, long-term growth faltering observed in many of the subjects.