THE NONRANDOMNESS OF THE DISTRIBUTION OF TRICHURIS-TRICHIURA AND ASCARIS-LUMBRICOIDES EGGS IN FECES AND THE EFFECT OF STIRRING FECAL SPECIMENS

Experiments were performed to describe the distribution of Trichuris t richiura and Ascaris lumbricoides eggs in faeces and to test for the e ffect of stirring faecal specimens prior to sampling. For each of 5 vo lunteers infected with A. lumbricoides and 7 volunteers infected with T. trichiura, helminth eggs were counted in 150 samples from a single stool specimen using the Kato-Katz smear technique. No significant dif ferences between the distribution of eggs in samples from the surface and the centre of the specimens were found. Prior to stirring, eggs we re found to be aggregately distributed in four of the specimens with T . trichiura and all of the specimens with A. lumbricoides. The distrib utions of eggs were not significantly altered by stirring the stool pr ior to sampling except in the case of one volunteer infected with A. l umbricoides for whom stirring reduced variability.