Abstract
The equine intestinal cestode Anoplocephala perfoliata
has been the subject of recent epidemiological and immunological studies
because of its suspected association with intestinal disease in the horse.
We have previously shown that the IgG(T) subtype antibody response to the
12/13 kDa component of the parasite excretory/secretory (E/S)
antigen is positively correlated with parasite intensity. In this study,
we utilize that correlation to examine the changes in natural infection
intensity with age. Infection intensity based on IgG(T) responses showed
a triphasic age-dependency pattern with peak mean worm burden in the 6
months–2 years age group, falling to a lower plateau level from 3
to 15 years, and rising again in older age groups. Anti-E/S total IgG
was found to have a convex age-dependency curve, with maximal response
in the 6 months–2 years old age group. IgG(a) showed a triphasic
response similar to the age-intensity profile of IgG(T); IgG(c) showed
steadily increasing levels of antibody with age. The IgG(b) age-dependency
profile was intermediate between IgG(a) and IgG(c). Age-specific correlation
coefficients between anti-12/13 kDa IgG(T) (as a measure of infection
intensity) and IgG(a) and IgG(b) revealed statistically significant values
for many age groups. The relative importance of exposure to infection and
the development of acquired immunity as determinants of the observed age-intensity
pattern is considered.