The Ascaris lumbricoides expelled by 1765 people in a poor urban community
in Bangladesh were recovered and counted after the subjects had been treate
d with pyrantel pamoate. The subjects were divided into 22 classes by age a
nd sex (mean n = 80) to examine how prevalence, mean worm burdens and measu
res of aggregation of worms varied with age and between the sexes, and to s
ee how a measure of aggregation, k, calculated in 3 ways (by maximum likeli
hood, from moments, or from the percentage uninfected) compared with an emp
irical aggregation index (the percentage of subjects who expelled an arbitr
ary 80% of all worms) and with the proportion who were moderately to heavil
y infected (defined as greater than or equal to 15 worms). The prevalence o
f infection ranged from 64% to 95%, mean worm burdens ranged from 7 to 23 w
orms, and k ranged from 0.3 to 1.2. There were significant differences betw
een adult males and females in the prevalence of infection, mean worm burde
ns and measures of aggregation, differences which are probably driven more
by behaviour than immunity. The parameter k was better described in terms o
f the proportion who were moderately to heavily infected (linear; range 0.1
5-0.58) than by the empirical aggregation index (non-linear; range 0.30-0.4
9).