Mapping of Schistosoma mansoni in the Nile Delta, Egypt: Assessment of the prevalence by the circulating cathodic antigen urine assay

Abstract

In line with WHO recommendations on elimination of schistosomiasis, accurate identification of all areas of residual transmission is a key step to design and implement measures aimed at interrupting transmission in low-endemic settings. To this purpose, we assessed the prevalence of active S. mansoni infection in five pilot governorates in the Nile Delta of Egypt by examining schoolchildren (6–15 years) using the Urine-Circulating Cathodic Antigen (Urine-CCA) cassette test; we also carried out the standard Kato-Katz (KK) thick smear, the monitoring and evaluation tool employed by Egypt’s national schistosomiasis control programme. Prevalence rates determined by the Urine-CCA test for all governorates were higher than those determined by KK (p<0.01). Of 35 districts surveyed in the five governorates, S. mansoni infection was detected in 19 districts (54.3%) using KK, and in 31 districts (88.6%) by Urine-CCA (χ2=9.94; P=0.0016). S. mansoni infections were detected by Urine-CCA, but not by KK in 12 districts (34.3%), and infection was not detected by either of the two diagnostic methods in four districts in Qalyubia governorate. Males and higher age-groups have significantly higher Urine-CCA prevalence rates. Based on the findings of the current S. mansoni mapping exercise, authorities of the Ministry of Health and Population (MoHP) adopted a new elimination strategy by readjusting thresholds for mass treatment with praziquantel and targeting all transmission areas. MoHP is now planning to remap in all other endemic governorates using Urine-CCA with the aim of identifying all areas of transmission where the elimination strategy should be applied.