Implications Of Intra- And Inter-specimen Fecal Egg Count Variations In Diagnosing Schistosoma Mansoni Infection By The Kato-katz Method In Workie Mado Village Kemise North-east Ethiopia

Examination of stool specimens by the Kato–Katz (K–K) technique has been a standardrnmethod for field diagnosis of intestinal Schistosomiasis. However, it has been debatedrnthat this technique has low diagnostic sensitivity due to intra- and inter-specimen fecalrnegg count variation. The relative contribution of these two sources of variation amongrn107 community members of Workie Mado village, northeast Ethiopia, which is knownrnfor its high endemicity of S. mansoni infection was quantified. The diagnostic yield ofrnexamining one, three, or five Kato–Katz thick smears prepared from one stool specimen,rnusing 41.7 mg templates was compared. In a subset of 11 volunteers, who had norndemonstrable eggs in their first five K–K thick smears, the advantage of examining twornadditional triplet K–K thick smears from stool specimens, taken in two subsequent daysrnwas assessed. The overall prevalence estimates of infections increased with increasingrnnumber of slides examined. Prevalence of S. mansoni infection based on single, triplet,rnand quintet K–K thick smears was 62.6%, 75.7% and 84.1%, respectively. Cumulativernprevalence obtained with two additional triplet Kato–Katz thick smears from 2nd and 3rdrnday stool specimens was 85.0% and 86.0%, which is not significantly different fromrnquintet measurement. Compared to quintet K–K thick smears, single K–K thick smearrnmissed 46.8%, 2.6% and 0% of subjects with light, moderate and heavy infections,rnrespectively, while triplet K-K thick smears missed 19.1% of light infections and 0% ofrnmoderate and heavy infections. We conclude that diagnostic sensitivity in such highrntransmission areas can be maximized by using quintet K-K thick smears from one stoolrnspecimen to reduce the number of missing lightly infected individuals, and therebyrnexamining smear-negative individuals with additional triplet K-K thick smears, fromrnsubsequent day stool specimens. Moreover, examining only one stool specimen withrnquintet K-K thick smears can also make reasonable estimates of S. mansoni infectionrnintensity, and it would be more feasible and less expensive approach than day-to-dayrnexamination of individuals in communities.rnKey words: Schistosoma mansoni, Kato-Katz technique, egg count, intra-specimen,rninter-specimen, Workie Mado village, Ethiopia.

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