Diagnosis of Soil-Transmitted Helminths in the Era of Preventive Chemotherapy: Effect of Multiple Stool Sampling and Use of Different Diagnostic Techniques

Abstract

BackgroundSoil-transmitted helminth infections are common throughout the tropics and subtropics and they disproportionately affect the poorest of the poor. In view of a growing global commitment to control soil-transmitted helminthiasis, there is a need to elucidate the effect of repeated stool sampling and the use of different diagnostic methods in areas targeted for preventive chemotherapy that are characterized by low-infection intensities. In this study, we focused on schoolchildren on Unguja Island, Zanzibar, an area where anthelminthic drugs have been repeatedly administered over the past decade.Methodology/Principal FindingsThree serial stool samples from each of 342 schoolchildren were examined using the Kato-Katz (K-K), Koga agar plate (KAP), and Baermann (BM) techniques. These methods were used individually or in combination for the diagnosis of Ascaris lumbricoides (K-K), Trichuris trichiura (K-K), hookworm (K-K and KAP), and Strongyloides stercoralis (KAP and BM). The examination of multiple stool samples instead of a single one resulted in an increase of the observed prevalence; e.g., an increase of 161% for hookworm using the K-K method. The diagnostic sensitivity of single stool sampling ranged between 20.7% for BM to detect S. stercoralis and 84.2% for K-K to diagnose A. lumbricoides. Highest sensitivities were observed when different diagnostic approaches were combined. The observed prevalences for T. trichiura, hookworm, A. lumbricoides, and S. stercoralis were 47.9%, 22.5%, 16.5%, and 10.8% after examining 3 stool samples. These values are close to the ‘true’ prevalences predicted by a mathematical model.Conclusion/SignificanceRigorous epidemiologic surveillance of soil-transmitted helminthiasis in the era of preventive chemotherapy is facilitated by multiple stool sampling bolstered by different diagnostic techniques.

Diversity of human intestinal helminthiasis in Lao PDR

“…Previous studies have shown that multiple Kato-Katz thick smears plus other diagnostic methods are mandatory to achieve a high diagnostic sensitivity. [21][22][23] In the present study, only 15 individuals (6.5%) were diagnosed as free of any intestinal parasite. It is conceivable that the actual number of parasite-free individuals is even lower, as some light infections might have been missed despite the rigorous diagnostic approach.…”

High prevalence of large trematode eggs in schoolchildren in Cambodia

“…Our findings on the cumulative sensitivities of Kato-Katz and FECT are in line with the observations of other authors: FECT is, in general, more sensitive than Kato-Katz for detection of LTE and the sensitivity of both techniques increases with multiple stool sampling (Glinz et al, 2010;Knopp et al, 2009Knopp et al, , 2008.…”

FLOTAC: A promising technique for detecting helminth eggs in human faeces

“…However, because of the low sensitivity of a single Kato-Katz, examinations of more than just one thick smear, ideally derived from multiple stool samples, are recommended for obtaining reliable results. 8 Obviously, repeated stool sampling reduces patient compliance, and increases overall costs. Economic evaluations of FLOTAC and its diagnostic potential for detection of eggs of other helminths (e.g.…”