Interactive and lag effects of environmental factors on the density of schistosome-transmitting Oncomelania hupensis: A twelve-year monthly repeated survey.

Schistosomiasis is a significant public health threat, and Oncomelania hupensis is the only intermediate host for schistosoma japonicum. We conducted 12-year monthly repeated surveys to explore the interactive and lag effects of environmental factors on snail density and to monitor their long-term and seasonal trends in a bottomland around the Dongting Lake region in China. Relevant environmental data were obtained from multiple sources. A Bayesian kernel machine regression model and a Bayesian temporal model combined with a distributed lag model were constructed to analyze interactive and lag effects of environmental factors on snail density. The results indicated the average annual snail density in the study site exhibited an increasing and then decreasing trend, peaking in 2013. Snail densities were the highest in October and the lowest in January in a year. Normalized Difference Vegetation Index (NDVI) and water level were the most effective predictors of snail density, with potential interactions among temperature, precipitation, and NDVI. The mean minimum temperature in January, water level, precipitation and NDVI were positively correlated with snail density at lags ranging from 1 to 4 months. These findings could serve as references for relevant authorities to monitor the changing trend of snail density and implement control measures, thereby reducing the occurrence of schistosomiasis.

Assessment of the influence of levees along Yangtze River on Oncomelania hupensis, the intermediate host of Schistosoma japonicum.

BACKGROUND: Oncomelania hupensis is the exclusive intermediate host of Schistosoma japonicum in China. Snail control is an essential component of schistosomiasis elimination programme. With 70 years of continuous efforts, the range of O. hupensis had reduced significantly, but slowed down in last decades. A large number of levees against flooding were constructed along Yangtze River and its affiliated lakes in the middle and lower reaches, which influenced the hydrology and ecology in the alluvial plains. The purpose of this study was to assess the impact of levees on the distribution of O. hupensis in the middle and lower reaches of the Yangtze River. METHODS: The snail habitats were digitalised by hand-held GPS system. The years for discovery and elimination of snail habitats were extracted from historical records. The accumulated snail-infested range for each habitat was calculated on the basis of annual reports. The current distribution of O. hupensis was determined by systematic and environmental sampling. The geographical distribution of levees was obtained from satellite imagery. To assess the impact of levees, the data pertaining to O. hupensis were divided into two parts: inside and outside the Yangtze River. Joinpoint regression was utilised to divide the study time span and further characterise the regression in each period. The 5-year-period moving averages of eliminated area infested by snails were calculated for the habitats inside and outside Yangtze River. The moving routes of corresponding geographical median centres were simulated in ArcGIS. Hotspot analysis was used to determine the areas with statistical significance clustering of O. hupensis density. RESULTS: Three periods were identified according to Joinpoint regression both inside and outside Yangtze River. The area infested by O. hupensis increased in the first two periods. It decreased rapidly outside Yangtze River year over year after 1970, while that inside the Yangtze River did not change significantly. Furthermore, the latter was significantly higher than the former. It was observed that the present density of O. hupensis inside Yangtze River was lower than outside the Yangtze River. The median centre for eliminated ranges inside Yangtze River wavered between the east (lower reach) and the west (middle reach). In contrast, the median centre for eliminated ranges continuously moved from the east to the west. CONCLUSIONS: Our findings indicated that the levees had a considerable negative impact on the distribution of O. hupensis outside Yangtze River. Some hotspots observed in the irrigation areas need a sluice system at the inlet of branch for snail control. The major distribution of O. hupensis located in Hubei might be caused by severe waterlogging. The intensive surveillance should be implemented there. The biggest two freshwater lakes, the major endemic regions historically, were identified as cold spots. The long-term impact of Three Gorges Dam on the distribution of O. hupensis in the lakes should be monitored and evaluated.

[Screening and functional analysis of differentially expressed long non-coding RNA in the liver of mice infected with Schistosoma japonicum during the chronic pathogenic stage].

OBJECTIVE: To screen differentially expressed long non-coding RNAs (lncRNAs) in the liver of mice infected with Schistosoma japonicum during the chronic pathogenic stage and identify their functions, so as to provide insights into unravelling the role of lncRNAs in S. japonicum infection-induced liver disorders. METHODS: Twenty 6-week-old C57BL/6 mice were randomly divided into two groups, of 10 animals each group. Each mouse in the experimental group was infected with (15 ± 2) S. japonicum cercariae via the abdomen for modeling chronic S. japonicum infection in mice, and distilled water served as controls. All mice were sacrificed 70 days post-infection, and mouse liver specimens were sampled for RNA extraction and library construction. All libraries were sequenced on the Illumina NovaSeq 6000 sequencing platform. Data cleaning was performed using the fastp software, and reference genome alignment and gene expression (FPKM) calculation were performed using the HISAT2 software. Potential lncRNA sequences were predicted using the software CNIC, CPC, Pfam, and PLEK, and potential lncRNAs were screened. Differentially expressed lncRNAs were screened with the DESeq2 software and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to identify biological processes and metabolic pathways involved in target genes of differentially expressed lncRNAs. RESULTS: A total of 333 potential lncRNAs were screened, and 67 were identified as differentially expressed lncRNAs, including 49 up-regulated and 18 down-regulated lncRNAs. A total of 53 target genes were predicted for differentially expressed lncRNAs. GO enrichment analysis showed that these target genes were mainly enriched in biological process and molecular function, among which Sema7a, Arrb1, and Ccl21b genes may be hub target genes for positive regulation of extracellular regulated protein kinase 1 (ERK1) and ERK2 cascades and may participate in the regulation of collagen expression. KEGG enrichment analysis showed that the target genes of differentially expressed lncRNAs were mainly enriched in cytokine-cytokine receptor interaction, viral protein interactions with cytokines and cytokine receptors, chemokine signaling pathway, and nuclear factor kappa-B (NF-κB) signaling pathway. CONCLUSIONS: This study identifies differentially expressed lncRNAs and functional enrichment of their target genes in the liver of mice during the chronic pathogenic stage of S. japonicum infection. Up-regulated lncRNAs may affect biological processes of ERK1/2 cascades and chemokine signaling pathways via target genes Sema7a, Arrb1, and Ccl21b, thereby affecting collagen expression and inflammatory signal pathways, ultimately affecting the development of liver disorders.