Comparison of novel and standard diagnostic tools for the detection ofinfection in Lao People's Democratic Republic and Cambodia

Background: Given the restricted distribution ofSchistosoma mekongi in one province in Lao People’s Democratic Republic (Lao PDR) and two provinces in Cambodia, together with progress of the national control programmes aimed at reducing morbidity and infection prevalence, the elimination of schistosomiasis mekongi seems feasible. However, sensitive diagnostic tools will be required to determine whether elimination has been achieved. We compared several standard and novel diagnostic tools inS. mekongi-endemic areas.Methods: The prevalence and infection intensity ofS. mekongi were evaluated in 377 study participants from four villages in the endemic areas in Lao PDR and Cambodia using Kato-Katz stool examination, antibody detection based on an enzyme-linked immunosorbent assay (ELISA) and schistosome circulating antigen detection by lateral-flow tests. Two highly sensitive test systems for the detection of cathodic and anodic circulating antigens (CCA, CAA) in urine and serum were utilized.Results: Stool microscopy revealed an overall prevalence ofS. mekongi of 6.4% (one case in Cambodia and 23 cases in Lao PDR), while that ofOpisthorchis viverrini, hookworm,Trichuris trichiura,Ascaris lumbricoides andTaenia spp. were 50.4%, 28.1%, 3.5%, 0.3% and 1.9%, respectively. In the urine samples, the tests for CCA and CAA detectedS. mekongi infections in 21.0% and 38.7% of the study participants, respectively. In the serum samples, the CAA assay revealed a prevalence of 32.4%, while a combination of the CAA assay in serum and in urine revealed a prevalence of 43.2%. There was a difference between the two study locations with a higher prevalence reached in the samples from Lao PDR.Conclusions: The CCA, CAA and ELISA results showed substantially higher prevalence estimates forS. mekongi compared to Kato-Katz thick smears. Active schistosomiasis mekongi in Lao PDR and Cambodia might thus have been considerably underestimated previously. Hence, sustained control efforts are still needed to break transmission ofS. mekongi. The pivotal role of highly sensitive diagnostic assays in areas targeting elimination cannot be overemphasised.