Is there added value from using three serial samples when surveying the occurrence of intestinal parasites in children?

BACKGROUND: Surveys for intestinal parasitic infections (IPIs) often involve samples from three sampling dates analysed by various microscopy techniques. However, analysis of three samples per individual is a huge burden on time and resources. We compared the value from analysing three or fewer samples.

METHODS: In this cross-sectional study, three faecal samples were collected every other day from 332 children from two locations in Guantanamo province, Cuba. Samples were analysed by wet mount with Lugol stain, Willis flotation method and Kato-Katz thick smear.

RESULTS: Most parasites were detected by wet mount, although helminth eggs not found by wet smear were detected by the Willis flotation method (in particular) and Kato-Katz smear. Blastocystis spp. was the most commonly detected parasite (about 65%), then Giardia duodenalis and then Entamoeba spp. Although analysis of two stool samples significantly increased occurrence data for Blastocystis, this was not so for the other parasites. For none of the protozoan parasites were results from analysing three samples significantly higher than results from analysing just two samples.

CONCLUSIONS: Analysing two faecal samples by wet mount and the Willis flotation method provides useful data for estimating the prevalence of IPIs in relatively high prevalence settings. Analysing further samples provides limited additional information and adds an extra burden in terms of time and resources.