Diagnostic Efficacy of Plasma-Based Real-Time PCR for Schistosomiasis Japonica in Mice before and after Treatment with Praziquantel

SIMPLE SUMMARY: Molecular diagnostic methods based on nucleic acid detection possess more advantages in high sensitivity and specificity, and low cross-reactivity with other pathogens. We assessed the detection efficacy of a real-time fluorescent quantitative PCR assay for schistosomiasis japonica in mice, before and after treatment with praziquantel. The sensitivity of the method was 99.3% (152/153, 95% CI: 96.41–99.98%) and its specificity was 100% (77/77, 95% CI: 95.32–100%). The results showed that the method exhibited good sensitivity and specificity, and its sensitivity correlated with the infection intensity in mice. After the oral administration of praziquantel, mice infected with 10 cercariae or 40 cercariae were all Schistosoma japonicum-negative via this method 6 weeks after treatment. This method had advantages over a soluble-egg-antigen-based enzyme-linked immunosorbent assay, and possessed better potential utility for evaluating the treatment efficacy of praziquantel in schistosome-infected mice. ABSTRACT: The prevalence of schistosomiasis japonica in China is now characterized by a low epidemic rate and low-intensity infections. Some diagnostic methods with high sensitivity and specificity are urgently needed to better monitor this disease in the current situation. In this study, the detection efficacy of a real-time fluorescent quantitative PCR (qPCR) assay was assessed for schistosomiasis japonica in mice, and before and after treatment with praziquantel (PZQ). Our results showed that the sensitivity of the qPCR was 99.3% (152/153, 95% CI: 96.41–99.98%) and its specificity was 100% (77/77, 95% CI: 95.32–100%) in mice infected with different numbers of Schistosoma japonicum. After the oral administration of PZQ, mice infected with 10 cercariae or 40 cercariae were all Schistosoma japonicum-negative 6 weeks after treatment. However, the negativity rates on a soluble egg antigen (SEA)-based enzyme-linked immunosorbent assay (ELISA) were only 34.8% (8/23, 10 cercariae group) and 6.7% (1/15, 40 cercariae group) at the sixth week after PZQ treatment. These results demonstrated that the qPCR method had good sensitivity and specificity, and suggested that its sensitivity correlated with the infection intensity in mice. Moreover, this method had better potential utility for evaluating the treatment efficacy of PZQ in schistosome-infected mice than SEA-based ELISA.