Laboratory Evaluation of a Basic Recombinase Polymerase Amplification (RPA) Assay for Early Detection of Schistosoma japonicum.

Early detection of Schistosoma japonicum (S. japonicum) within its intermediate and definitive hosts is crucial for case finding and disease surveillance, especially in low-endemic areas. Recombinase polymerase amplification (RPA) has many advantages over traditional methods of DNA-amplification, such as polymerase chain reaction (PCR), including high sensitivity and specificity whilst being deployable in resource-poor schistosomiasis-endemic areas. Here, we evaluated the performance of a basic RPA assay targeting the 28srDNA gene fragment of S. japonicum (Sj28srDNA) using schistosome-infected Oncomelania hupensis (O. hupensis) and mouse models, compared to the traditional pathological method and a PCR assay. Overall S. japonicum infection prevalence within O. hupensis hosts by microscopic dissection, PCR and RPA was 9.29% (13/140), 32.14% (45/140) and 51.43% (72/140), respectively, presenting significant differences statistically (χ2 = 58.31, p < 0.001). It was noteworthy that infection prevalence by PCR and RPA performed was 34.44% (31/90) and 53.33% (48/90) in snails within 6 weeks post-infection, while the dissection method detected all samples as negatives. In addition, the basic RPA assay presented positive results from the fourth week post-infection and third day post-infection when detecting fecal DNA and serum DNA, respectively, which were extracted from a pooled sample from mice infected with 20 S. japonicum cercariae. This study suggests that the RPA assay has high potential for early detection of S. japonicum infection within its intermediate and definitive hosts.