Occurrence of Strongyloides stercoralis in Yunnan Province, China, and Comparison of Diagnostic Methods

Abstract

Background Strongyloides stercoralis is a neglected soil-transmitted helminth species, and there is a lack of parasitologic and epidemiologic data pertaining to this parasite in China and elsewhere. We studied the local occurrence of S. stercoralis in a village in Yunnan province, China, and comparatively assessed the performance of different diagnostic methods.Methodology/Principal FindingsMultiple stool samples from a random population sample were subjected to the Kato-Katz method, an ether-concentration technique, the Koga agar plate method, and the Baermann technique. Among 180 participants who submitted at least 2 stool samples, we found a S. stercoralis prevalence of 11.7%. Males had a significantly higher prevalence than females (18.3% versus 6.1%, p = 0.011), and infections were absent in individuals <15 years of age. Infections were only detected by the Baermann (highest sensitivity) and the Koga agar plate method, but neither with the Kato-Katz nor an ether-concentration technique. The examination of 3 stool samples rather than a single one resulted in the detection of 62% and 100% more infections when employing the Koga agar plate and the Baermann technique, respectively. The use of a mathematical model revealed a ‘true’ S. stercoralis prevalence in the current setting of up to 16.3%.Conclusions/SignificanceWe conclude that S. stercoralis is endemic in the southern part of Yunnan province and that differential diagnosis and integrated control of intestinal helminth infections needs more pointed emphasis in rural China.

Prevalence of Strongyloides stercoralis and other intestinal parasitic infections among mentally retarded residents in central institution of southern Iran

“…According to the high prevalence of strongyloidiasis in the rehabilitation care center, the true prevalence would be higher if specific diagnostic methods such as Baermann technique and agar plate culture method were used [11,32,33] .…”

“…Serological methods can reveal light infections in asymptomatic individuals and should be used for further studies among those population [11,15,32] and in order to achieve real prevalence, screening procedures must be applied.…”

“…Soil-transmitted helminthes (STH) as a major health problem caused by Ascaris lumbricoides, Trichuris trichiura and the hookworms are the most prevalent worldwide [7] and, Strongyloides stercoralis (S. stercoralis) is the most neglected one among them [9,11,12] . It is estimated that over 1 billion people are infected with STH and 30-100 millions with S. stercoralis worldwide [7,[11][12][13][14] .…”

“…It is estimated that over 1 billion people are infected with STH and 30-100 millions with S. stercoralis worldwide [7,[11][12][13][14] . S. stercoralis's unique life cycle makes it possible to survive in human host and causes autoinfection to lead chronic disease which could have remained for several years [13][14][15] .…”

Strongyloidiasis – the most neglected of the neglected tropical diseases?

“…In a populationbased study in China, combining diagnostic approaches and repeated examinations resulted in an unexpectedly high prevalence of 11.7%. 15 Using a similar approach, Strongyloides was shown to be a very common parasite (prevalence 10.6%) in northern Ghana. 16 In a recent study in Mozambique (unpublished data) careful examinations of direct smears and formol ether concentration sediments showed 9% and 12% of the population to be infected, while a combination of culture, Baermann concentration and PCR revealed a prevalence of 48%.…”