Da-Bing Lu

China was once a major endemic zone for Schistosoma japonicum, but decades of control efforts have dramatically reduced transmission. Suzhou City, in Jiangsu Province, a former hyperendemic area, achieved transmission interruption in 1995. However, the intermediate host Oncomelania hupensis persists and new habitats in non-endemic villages pose resurgence risks if parasites are reintroduced. To evaluate genetic resilience and dispersal potential, we analyzed six O. hupensis populations (214 snails) from ecologically distinct habitats in Wuzhong district, Suzhou (2018 to 2021): Guangfu (GF20 and GF21: wetlands), Jinting (JT18, JT19, and JT20: isolated island), and Dongshan (DS19: lakeside hills). Using nine microsatellite loci, we identified 91 alleles and assessed genetic diversity, structure, and demography. All populations exhibited low observed heterozygosity (Ho < 0.5), with bottlenecks detected in GF21, GF20, and JT20. Paradoxically, infinite effective population sizes (Ne) at 95% CI upper limits suggested retained adaptive potential. Significant genetic differentiation (F_ST = 0.287, p < 0.01) reflected habitat-driven isolation: Jinting’s island populations diverged markedly from Dongshan and Guangfu, while bidirectional gene flow (Nm > 1) between Guangfu’s temporally sampled populations indicated sustained genetic connectivity over time. DIYABC modeling traced JT20’s ancestry to admixture between Jinting (JT18) and Guangfu (GF20) sources, implicating flood-mediated dispersal. Despite local control efficacy, snails retain resilience via large Ne. These findings mandate habitat-tailored strategies: habitat modification and intensified molluscicide campaigns in Guangfu and targeted eradication of Jinting’s isolated populations. Integrating genetic surveillance into snail monitoring programs will be critical to sustaining transmission interruption and achieving elimination in ecologically complex regions.

Following the exciting announcement that Anhui Province, one of the historically most heavily Schistosoma japonicum endemic regions in China, has been officially declared to have achieved the goal of province-wide transmission interruption of schistosomiasis, we raise two concerns that merit further consideration. Firstly, S. japonicum is zoonotic, and in China it is known that humans, livestock, and wild animals such as rodents are major reservoirs of infection. While S. japonicum infections both in humans and bovines have recently been reduced to zero prevalence, infection persists at moderate to high levels within rodents with, for example, prevalence’s reported of up to 12.81% within Anhui Province over last 5 years. Therefore, surveillance of schistosome infections in wild animals, at least in rodents, must be included in the criteria of verifying transmission interruption or elimination in China. Secondly, regarding how the official procedure of verification of transmission of interruption was assessed, we propose that a more accurate survey design and foci selection would be based, at least in part, upon areas where schistosome infections in either humans, domestic/wild animals and/or snails have recently been documented. This is particularly urgent, not only in terms of the long-term sustainability of disease control in China, but because many other countries are now fully acknowledging the zoonotic potential of schistosomiasis and are/or will soon enter this final elimination phase as officially outlined in the WHO’s 2021–2030 Neglected Tropical Diseases Roadmap.

Advanced schistosomiasis is the most serious outcome of infection and has a negative impact on both physical fitness and mental health of patients, the latter of which has long been overlooked. Therefore, we performed this systematic review and meta-analysis to estimate the overall prevalence of depressive symptoms, one of the most common mental problems, in patients with advanced schistosomiasis in China. Six electronic databases were searched for studies reporting the prevalence of depressive symptoms in the targeted patients. Assessments were pooled using a fixed- or random-effects model based on heterogeneity test. Subgroup analyses were further performed and differences between/among groups were examined using the chi-squared test. The protocol had previously been registered in PROSPERO (CRD42023406708). A total of 11 studies with 1,673 participants were included. The pooled prevalence of depressive symptoms in advanced schistosomiasis in China was 62.01% (95% CI: 51.30% - 72.72%), with a significant heterogeneity among studies. Depressive symptoms were more prevalent in patients with complications and more than half of the patients suffered a mild- or moderate-level of depression. No publication bias was found, and sensitivity analysis showed a stable result. The overall prevalence of depressive symptoms in advanced schistosomiasis in China was high enough to warrant psychotherapeutic interventions, especially for patients with complications. This would greatly prevent or/and reduce depression and improve their quality of life. Schistosomiasis is a neglected tropical disease (NTD) which affects more than 250 million people across 78 countries worldwide. The three major schistosomes infecting humans are Schistosoma mansoni, S. japonicum, and S. haematobium. In China, after 70 years of control efforts, tremendous progress has been made, and now the number of schistosomiasis japonica infections is at its lowest historical level. However, advanced schistosomiasis, which is the most serious outcome of schistosome infection, poses a great threat as an increasing number of the patients have been diagnosed. Depression is a frequently occurring mental health issue caused by the disease that has long been overlooked. Therefore, we performed this meta-analysis to estimate the overall prevalence of depressive symptoms in patients with advanced schistosomiasis in China and its possible influential factors. We found that the pooled prevalence was 62.01% (95% CI: 51.30% - 72.72%) in the targeted patients and the estimate was associated with complications of the disease. Our study would call for psychological interventions to improve quality of life for patients with advanced schistosomiasis.

Schistosoma japonicum is one of the major infectious agents of human schistosomiasis, mainly endemic in China and the Philippines. We have previously reported the finding of two schistosome isolates, each with a different cercarial emergence pattern adapted to their different hosts. However, there are currently no whole-genome sequencing studies to investigate the underlining genetics of the adaptive traits. We sampled schistosomes in 2013 and 2020 from a hilly area Shitai (ST) and a marshland area Hexian (HX) of Anhui, China. Ten to 15 male or female adult worms from each site/year were sent for whole genome sequencing. Genetics were analyzed, and selection signals along genomes were detected. Gene enrichment analysis was performed for the genome regions under selection. The results revealed considerable genetic differentiation between the two isolates. The genome “windows” affected by natural selection were fewer in ST (64 windows containing 78 genes) than in HX (318 windows containing 276 genes). Twelve significantly enriched genes were identified in ST, but none in HX. These genes were mainly related to specific DNA binding and intercellular signaling transduction. Some functional region changes identified along the genome of the hilly schistosome may be related to its unique late afternoon cercarial emergence.

Schistosoma japonicum had once caused the greatest disease burden in China and has still been transmitted in some hilly areas, for example, in Shitai of Anhui province, where rodents are projected to be the main reservoir. This may lead to a critical need of molecular tools with high efficiency in monitoring the dynamic of the rodent-associated S. japonicum, as an appropriate amount of schistosome input can re-establish its life cycle in a place with snails and then result in the re-emergence of schistosomiasis. Therefore, the goal of this study was to develop high polymorphic microsatellites from the whole genome of rodent-associated S. japonicum strain to monitor its transmission dynamic. We sampled the hilly schistosome isolate from Shitai of Anhui in China and sequenced the parasite with the next-generation sequencing technology. The whole genome was assembled with four different approaches. We then developed 71 microsatellite markers at a genome-wide scale throughout two best assembled genomes. Based on their chromosome mapping and the expected length of targeted sequences, we selected 24 markers for the development of multiplex reactions. Two multiplexes composed of 10 loci were finally developed, and their potential was revealed by their successful application on and capturing the genetic diversity of three schistosome populations. The selected 10 markers, each with clear chromosome location and characteristics, will be greatly useful in tracing the dispersal pathways or/and dynamics of the rodent-associated S. japonicum or others in the hilly area of China or elsewhere.

Schistosome japonicum had once caused the greatest disease burden in China, and has still been transmitted in some hilly areas, for example in Shitai of Anhui province, where rodents are projected to be the main reservoir. This may lead to a critical need of molecular tools with high efficiency in monitoring the dynamic of the rodent-associated S. japonicum, as an appropriate amount of schistosome input can re-establish its life cycle in a place with snails and then result in the re-emergence of schistosomiasis. We sampled the hilly schistosome isolate from Shitai of Anhui in China and sequenced the parasite with the next-generation sequencing technology. The whole genome was assembled with four different approaches. We then developed 71 microsatellite markers at a genome-wide scale throughout two best assembled genomes. Based on their chromosome mapping and the expected length of targeted sequences, we selected 24 markers for the development of multiplex reactions. Two multiplexes composed of 10 loci were finally developed, and their potential were revealed by their successful application on and capturing the genetic diversity of three schistosome populations. The selected 10 markers, each with clear chromosome location and characteristics, will be greatly useful in tracing the dispersal pathways or/and dynamics of the rodent-associated S. japonicum or others in the hilly area of China or elsewhere.