Dongting Lake Region Research Articles

Identification of optimum scopes of environmental drivers for schistosome-transmitting Oncomelania hupensis using agent-based model in Dongting Lake Region, China.

Oncomelania hupensis (O. hupensis), the sole intermediate host of Schistosoma japonicum, greatly influence the prevalence and distribution of schistosomiasis japonica. The distribution area of O. hupensis has remained extensive for numerous years. This study aimed to establish a valid agent-based model of snail density and further explore the environmental conditions suitable for snail breeding. A marshland with O. hupensis was selected as a study site in Dongting Lake Region, and snail surveys were monthly conducted from 2007 to 2016. Combined with the data from historical literature, an agent-based model of snail density was constructed in NetLogo 6.2.0 and validated with the collected survey data. BehaviorSpace was used to identify the optimal ranges of soil temperature, pH, soil water content, and vegetation coverage for snail growth, development and reproduction. An agent-based model of snail density was constructed and showed a strong agreement with the monthly average snail density from the field surveys. As soil temperature increased, the snail density initially rose before declining, reaching its peak at around 21°C. There were similar variation patterns for other environmental factors. The findings from the model suggested that the optimum ranges of soil temperature, pH, soil water content and vegetation coverage were 19°C to 23 °C, 6.4 to 7.6, 42% to 75%, and 70% to 93%, respectively. A valid agent-based model of snail density was constructed, providing more objective information about the optimum ranges of environmental factors for snail growth, development and reproduction.

Distribution dynamics of waterbirds in Dongting Lake and surrounding lakes

Abstract Dongting Lake and the lakes surrounding it are spatially relatively independent, yet they form an inseparable integrated system for waterbirds. Understanding the changes in waterbird distribution pattern in Dongting Lake and surrounding lakes is important for waterbird conservation and management. Based on six surveys during the winter period of waterbird and habitat data, we studied the changes in distribution pattern of different functional group of waterbirds between Dongting Lake and surrounding lakes and explored the effect of habitat area in Dongting Lake on waterbird distribution. The results revealed that the habitat areas within Dongting Lake are larger but less stable, whereas those in the surrounding lakes are much smaller but more stable. During regular hydrology periods, waterbirds were mainly distributed in Dongting Lake, whereas most of the diving ducks and vegetation gleaners occurred in surrounding lakes; during extreme dry periods, many waterbirds shifted to surrounding lakes (e.g., dabbling ducks and gulls). The Percentage Similarity Index (PSI) of these groups, which reflects waterbirds’ distribution dynamics, exhibited negative correlations with changes in water area within Dongting Lake. The percentages of these water-dependent groups and water area in Dongting Lake exhibited a positive correlation. Water area in Dongting Lake could reflect the distribution pattern of waterbirds between Dongting Lake and surrounding lakes. Our results emphasize the importance of the overall protection of wetlands in the Dongting Lake region.

The feeding preference and bite response between Microtus fortis and Broussonetia papyrifera.

Broussonetia papyrifera is a dioecious plant that is rich in various metabolites and widely distribute in Asia. Microtus fortis is a rodent that often causes damage to crops, especially in the Dongting Lake region of China. There is a wide overlap in the distribution areas for the above species and the M. fortis feeds on the leaves of the B. papyrifera. Preliminary experiments have shown that the reproduction of M. fortis is inhibited after feeding on the leaves of the B. papyrifera. In order to explore the potential of using B. papyrifera to develop botanical pesticides, we investigated the palatability and reactive substances. The feeding frequency of M. fortis on B. papyrifera leaves to that of on daily fodder and Carex brevicuspis that is the primary food for the wild population were compared. We also attempted to identify the responsive substances in B. papyrifera leaves that were bitten by M. fortis using metabolome analysis. In general, B. papyrifera leaves exhibited a stronger attraction to M. fortis. M. fortis foraged B. papyrifera leaves more frequently, and the intake was higher than that of the other two. Differential metabolites were screened by comparing normal leaves and leaves bitten by M. fortis, meanwhile with the intervention of clipped leaves. A total of 269 substances were screened, and many of these were involved in the biosynthesis of secondary metabolites, including terpenoids and alkaloids. These substances may be related to the defense mechanism of B. papyrifera against herbivores. These findings support further research examining animal-plant interactions and simultaneously provide insights into the utilisation of B. papyrifera resources and the management of rodents. The good palatability and the defense of B. papyrifera leaves suggest that they have the potential to contribute in development of plant rodenticide.

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.

Ecological resilience in water-land transition zones: A case study of the Dongting Lake region, China

Water-land transition zones (WLTZs) are quintessential, complex human-land systems where aquatic and terrestrial environments intermingle, playing a pivotal role in bolstering global ecological resilience (ER). Human terrestrial production activities have encroached upon ecologically sensitive aquatic areas, weakening the inherent ER patterns in WLTZs. To address these issues, we developed an ER assessment process chain across the disturbance-carrying-recovery (D-C-R) dimensions. Applied it to the Dongting Lake region, this model diagnosed the spatiotemporal variations in ER from 2000 to 2020 and revealed the stress mechanisms of various driving factors. The results indicate: (1) The ER spatial pattern in the Dongting Lake region featured a radiating enhancement structure originating from a low-value core in the central plain’s lake network area, displaying distinct water-land gradient variations. Areas with declining ER levels were mainly distributed around the main body of the lake, water system runoff areas, and near governmental centers. (2) The spatiotemporal differentiation effects of ER manifested as an east–west axial development trend, tending toward polarization. The spatiotemporal aggregation effect appeared as L-L clustering and cold spots in the north, gradually expanding toward the peripheral forest areas. (3) Factors related to land use were the dominant drivers of spatiotemporal changes in ER. Simultaneously, the nonlinear interaction intensity among these driving factors showed a significant annual increase. This research framework can be extended to assess ER in similar regions, potentially offering policy recommendations for the ecological protection and sustainable management of WLTZs.

An integrated model chain for diagnosing and predicting conflicts between production-living-ecological space in lake network regions: A case of the Dongting Lake region, China

The disorderly expansion of human production-living construction activities into aquatic ecological sensitive areas has triggered severe production-living-ecological space (PLES) conflicts. However, research on the risk-triggering mechanisms of PLES conflicts in lake network regions and multidimensional scenario simulation techniques is relatively lacking. To address these issues, this study constructs an integrated model chain by coupling the Markov-GMOP-PLUS model to achieve a quantified diagnosis and simulated regulation of spatial conflict strength index (SCSI) under sustainable development goals. Applying it to the Dongting Lake region reveals that: (1) The overall PLES exhibited a distribution pattern where “ecological space encompasses production space, with living space interspersed within”. The category conversion mainly reflected the encroachment of agricultural production space on the plain water ecological space, with a conversion area of up to 899.48 km2. (2) The distinctive “high in the north, low in the south” PLES conflict pattern was closely aligned with the land use structure and water system distribution, with conflict hotspots persistently clustering in the core lake network regions amid rapid urbanization. Among these, the growth rate of severe conflicts in the last ten years was 3.86 times that of the previous ten years. (3) The sustainable development scenario showcased the most effective conflict mitigation by curtailing production-living space expansion and ecological space encroachment. This scenario reversed the growth trend in conflict high-value zones and the reduction trend in low-value zones, with change rates of −3.30 % and 7.05 %, respectively, compared to 2020. This study provides a scientific basis for formulating sustainable land-use policies in lake network regions.

Exploring the impacts of land use and land cover change on ecosystem services in Dongting Lake, China: a spatial and temporal analysis

Background and objectives: Land use and land cover change (LULCC) directly affects the human living environment and economic society by influencing ecosystem services. This study explores the complex relationship between LULCC and ecosystem services in the Dongting Lake region of China.Methods: The analysis incorporates the transfer matrix analysis of LULCC, ecosystem service value (ESV) accounting, Mann–Kendall mutation test, gray correlation, and path analysis. This study explored the spatial and temporal characteristics of LULCC and ecosystem services and revealed the comprehensive impacts of LULCC on ecosystem services from the perspective of factor interactions.Findings: The findings reveal that open water (OW) area and farmable land are the dominant land use types transferring in and out of the study area, with significant interconversion observed among open water area, wetland (WL), arable land (AL), and forest land (FL). Water conservation, waste disposal, climate regulation, and biodiversity conservation emerge as the most crucial ecosystem services in the study area. The study identifies consistent patterns of abrupt changes in LULCC and ESV across six analyzed time periods. Forest land exhibits the most substantial direct influence on climate regulation, gas exchange, soil formation and protection, conservation of biodiversity, raw materials, and recreation and leisure. Additionally, forest land, wetland, arable land, and open water area contribute significantly to the total ESV, with forest land being the dominant factor influencing the spatial differentiation of ecosystem services in the Dongting Lake region.Conclusion: The research reveals the consistency of ecosystem services and LULCC trends in the Dongting Lake area. LULCC is a complex process influenced by multiple factors, in which the conversion between ecological and non-ecological land use has a significant impact, and the complex coupling and coordination among LULCC drivers together influence ecosystem services. Furthermore, LULCC alters the structure and scale of ecosystems, resulting in alterations in the ESV.

Extreme drought alters waterfowl distribution patterns and spatial niches in floodplain wetlands

The Yangtze River Basin was among the areas most severely affected by the widespread extreme drought in the Northern Hemisphere in 2022. Drought conditions in this basin extended into the wintering season, significantly influencing waterfowl habitat availability. Exploring how waterfowl distributions and ecological niches respond to these changes in wetland environmental conditions and the underlying ecological mechanisms are important for biodiversity conservation and understanding wetland ecological processes. By integrating field observations, remote sensing, and ecological niche modelling, we analysed habitat changes over the past decade and investigated how extreme drought affected the distribution patterns and spatial niches of two waterfowl guilds, ducks and geese, in the Dongting Lake Region, a key wetland ecosystem in the Yangtze River Basin. The extreme drought led to a drastic reduction in the waterbody area of natural habitats and caused vegetation to enter the wilting stage prematurely. In response, a substantial proportion of waterfowl shifted to adjacent managed wetlands with stable water levels, especially the ducks, whose distribution pattern was fundamentally altered. The proportion of both waterfowl guilds in the managed wetland showed a significant correlation with the proportion of the waterbody area. Further, we compared the spatial niche of waterfowl in 2022 with that in the former year, which represented a typical year with normal hydrology. The spatial niche of ducks underwent a substantial contraction, while that of geese remained large in both years but shifted inward in 2022 towards areas with lower elevation, and foraging resource use was altered. Therefore, for both waterfowl guilds, the extent of habitat overlap between the two years was small. This study has important implications for understanding the impact of extreme climatic and hydrological events on wetland ecosystems. Furthermore, our results emphasise the importance of water level-managed wetlands for biodiversity conservation.

Spatial–temporal patterns of ecological changes in the Dongting Lake region and their responses to climate factors and human activities

ABSTRACT The Dongting Lake region is an important ecological and environmental protection zone in the Yangtze River Economic Belt of China. Long-term monitoring and evaluation of its ecological environment is of great significance. In this study, the spatio-temporal pattern of ecological condition change and its response to climate factors and human activities in the Dongting Lake region was quantitatively analyzed using RSEI (Remote Sensing Ecological Index) model. The primary conclusions are as follows: (1) The temporal pattern of ecological changes has a small fluctuation period (1990–2007) and a continuous improvement period (2007–2020) with an ecological improvement rate of 1.17% per year. (2) The spatial pattern of ecological changes is directly tied to the land use types in this area. 17.36% of the regions with an excellent ecological level are primarily woodland, whereas 4.45% of the areas with a low ecological level are mostly urban. (3) The deterioration in ecological conditions in urban areas is primarily attributable to human activities, whereas the decline in ecological conditions in surrounding mountainous regions and central agricultural regions is primarily attributable to climate factors. Our research provides valuable support for ecological environment monitoring and management strategy formulation in the Dongting Lake region.

PDFID: A high-resolution flood inundation dataset with a long time series

Study regionPoyang Lake and East Dongting Lake, China. Study focusOn the basis of data on the extent of the inundation of water bodies, the water level, and DEM data, this study constructed an hourly flood inundation dataset (PDFID) for the East Dongting Lake and Poyang Lake regions with a 10 m resolution and a coverage area of >5000 km2 from 2012 to 2022 by using the RFim model and the U-net model. Validation of the results on Sentinel-1 SAR images and Sentinel-2 MSI optical images showed that the overall accuracy of the dataset ranged from 88% to 97%, with a kappa coefficient ranging from 0.601 to 0.932. The accuracy for the East Dongting Lake region ranged from 88% to 97%, with a kappa coefficient of >0.67, and for the Poyang Lake region, the accuracy ranged from 89% to 97%, with a kappa coefficient of >0.6. New hydrological insights for the regionFlood inundation datasets with a high spatiotemporal resolution and long time series enable us to analyze and comprehend floods’ processes, patterns, and dynamics, facilitating the enhanced development and management of flood prevention and mitigation strategies. However, they have yet to be made available. Thus, this study can provide a fundamental data source for analytical mining and predicting the flooding processes in basins.

Effects of Summer and Autumn Drought on Eutrophication and the Phytoplankton Community in Dongting Lake in 2022.

Since July 2022, the Yangtze River basin has experienced the most severe hydro-meteorological drought since record collection started in 1961, which has greatly affected the ecological environment of the Dongting Lake (DTL) basin. To investigate the effects of drought events on the eutrophication and phytoplankton community structure of DTL, the lake was sampled twice in August and September 2022 based on the water level fluctuations resulting in 47 samples. Furthermore, we combined the comprehensive trophic level index (TLI) and phytoplankton Shannon-Wiener diversity index (H) to characterize and evaluate the eutrophication status. The key influencing factors of the phytoplankton community were identified using redundancy analysis (RDA), hierarchical partitioning, and the Jaccard similarity index (J). Our results showed that the TLI of DTL changed from light-moderate eutrophication status (August) to mesotrophic status (September), whereas the H changed from light or no pollution to medium pollution. The phytoplankton abundance in August (122.06 × 104 cells/L) was less than that in September (351.18 × 104 cells/L) in DTL. A trend in phytoplankton community succession from Bacillariophyta to Chlorophyta and Cyanophyta was shown. The combination of physiochemical and ecological assessment more accurately characterized the true eutrophic status of the aquatic ecosystem. The RDA showed that the key influencing factors in the phytoplankton community were water temperature (WT), pH, nitrogen and phosphorus nutrients, and the permanganate index (CODMn) in August, while dissolved oxygen (DO) and redox potential (ORP) were the key factors in September. Hierarchical partitioning further indicated that temporal and spatial variations had a greater impact on the phytoplankton community. And the J of each region was slightly similar and very dissimilar, from August to September, which indicated a decreased hydrological connectivity of DTL during drought. These analyses indicated that the risk to the water ecology of DTL intensified during the summer-autumn drought in 2022. Safeguarding hydrological connectivity in the DTL region is a prerequisite for promoting energy flow, material cycle, and water ecosystem health.

Monitoring and control of water-ecological space in the Dongting Lake region

The territorial spatial planning in the new era strengthens the control of different functional spaces and emphasizes integrated and coordinated development of each functional space. Therefore, it is important to monitor the “structure-function” characteristics of water-ecological space based on the context of territorial spatial planning and develop a management and control framework. Based on land use and social statistics, and with the help of ArcGIS analysis, this paper examined the structure and function of the water-ecological space in the Dongting Lake study for 2010, 2015, and 2020, generating a control framework and proposing key initiatives. The main results are as follows: 1) The overall scale of the water ecological space in the Dongting Lake study is over 7,300 km2. Water bodies had the largest share, followed by coastal terrestrial areas, while the land-water ecotone was the smallest. There was a small decrease in the water ecological space during the study period. Yueyang had the largest overall scale of water ecological space, while Linli had the smallest. 2) The comprehensive function of water ecological space in the Dongting Lake study was about 0.4000, increasing somewhat during the study period. Among the units, the comprehensive function value was highest in Yuanjiang City, while Jincheng City had the lowest. 3) From the structural elements of water ecological space, scientific planning of functional zoning of water ecological space should be carried out and combined with the delineation of “three zones and three lines.” Key initiatives such as multi-scale and multi-level planning and control, use control and access restrictions, determination of water ecological space ownership, pollution control and accountability, and comprehensive water ecological treatment and restoration should be promoted.

The climate adaptive characteristics of urban inside/outside water bodies based on their cooling effect in Poyang and Dongting lake regions, China

Most publications have focused on the cooling effect of urban inside water bodies. However, the climate adaptive characteristics of urban inside/outside water bodies is seldom studied. In this paper, three types of water bodies, i.e., urban inside water bodies, urban outside discrete water bodies and large water bodies are identified according to their relative spatial relationships with built-up areas. The climate adaptive landscape characteristics of water bodies are analyzed based on water bodies’ cooling effect (WCE) inside and outside cities in the Poyang Lake and Dongting Lake regions. Seventy-three Landsat TM/OLI/TIRS images acquired from 1989 to 2019 are employed. Landscape scale characteristics of urban inside/outside water bodies are described by area, water depth, perimeter to area ratio (PARA) and distance-weighted area index (DWAI). Three temperature-related parameters are calculated to estimate the WCE in different conditions. Climate adaptive characteristics of water bodies inside/outside cities are determined by correlation and regression analysis. Results show that: 1) The long river shape, depth, orientation and fluidity of urban inside water bodies are benefit to enhance their cooling effect; 2) the distance of urban outside water bodies from built-up areas are positive correlated with their cooling effect; 3) the optimal acreage of large water bodies are >2500 km2 and 1111–1287.5 km2 for climate adaption of Poyang Lake and Dongting Lake, respectively. Simultaneously, the WCE of urban outside large water bodies is related with human activities and climate conditions. The results of our study provide a significant contribution to blue-space planning in cities, and provide insights into actionable climate adaption planning in inland large lake areas.

The Impact of Land Use and Landscape Pattern on Ecosystem Services in the Dongting Lake Region, China

Ecosystem services (ES) are directly affected by land use and land cover changes (LUCC); however, the impacts of extended period LUCC on ES are poorly explored. Here, we mapped the 1998–2019 annual land use and land cover in the Dongting Lake Region (China) and explored the spatiotemporal evolution of LUCC and landscape patterns (i.e., composition, shape, and aggregation) and their relationship with ES, including carbon storage, gross primary production (GPP), water conservation capacity, and crop yield in the region. The results showed a significant increase in forest areas and impervious surfaces and a decrease in croplands and bare lands with spatial heterogeneity. Carbon storage was strongly correlated with forest, cropland, waterbody, impervious surface, and bare land, and there was a nonlinear relationship between landscape patterns and ES. The trade-offs and synergies (correlations) among ES varied considerably, with crop yield being significantly synergistic with carbon stocks, GPP, or GPP with carbon stocks. This study revealed the nonlinear relationship between landscape patterns and ES, and the mechanism of landscape characteristics on ES. The findings can provide scientific support for regional land use planning, ES regulation, and landscape optimization in the lake region.

The Climate Adaptive Characteristics of Urban Inside/Outside Water Bodies Based on Their Cooling Effect in Poyang and Dongting Lake Regions, China

The Climate Adaptive Characteristics of Urban Inside/Outside Water Bodies Based on Their Cooling Effect in Poyang and Dongting Lake Regions, China

Environmental Determinants for Snail Density in Dongting Lake Region: An Ecological Study Incorporating Spatial Regression.

This study explored the environmental determinants of different months on snail density measured in April at different types of snail habitats (marshlands, inner embankments, and hills) by considering spatial effects. Data were gathered from surveys on snails that were conducted in Hunan Province in April 2016, and information was collected on environmental variables. To investigate the environmental factors influencing snail density in various types of snail habitats, the ordinary least square model, spatial lag model, and spatial error model were all used. The environmental determinants for snail density showed different effects in the three types of snail habitats. In marshlands, snail density measured in April was associated positively with the normalized difference vegetation index (NDVI) and was associated negatively with flooding duration and annual hours of sunshine. Extreme temperatures correlated strongly to snail density measured in April (P < 0.05). In areas inside embankments, snail density measured in April increased with a decreased distance between snail habitat and the nearest river (P < 0.05). In hills, extreme heat, annual hours of sunshine, NDVI in September, and annual average land surface temperature (LST) were associated negatively with snail density measured in April, whereas index of moisture (IM) was associated positively with snail density measured in April (P < 0.05). The effects of LST and hours of sunshine on snail density measured in April varied with months of the year in the three different types of snail habitats (P < 0.05). Our study might provide a theoretical foundation for preventing snail transmission and subsequent spread of schistosomiasis.

Spatiotemporal assessment of water security in the Dongting Lake region: Insights from projection pursuit method and sparrow search algorithm

The Dongting Lake region (TDLR) is China's essential commodity grain base and inland wetland reserve. Few studies, however, focus on the water security of TDLR. Additionally, as the attributes of water security increase, common methods may not obtain more structural characteristics or make full use of the data, resulting in the evaluation not being comprehensive enough. Hence, based on the vulnerability scoping diagram (VSD) and the coupled model combining projection pursuit method (PP), sparrow search algorithm (SSA), and contribution degree model, this study assesses the water security of TDLR and its three major cities. The result shows that the coupled model may be suitable to assess water security since it obtains a more accurate, comparable, sensitive, comprehensive evaluation more rapidly, intuitively, and stably. The water security of TDLR and three cities all exhibit an overall fluctuating upward trend during 2011–2020, with a significant increase in the comprehensive water security evaluation value (WSV) of TDLR (p < 0.05). Among the three cities, the water security of Yiyang is the safest, followed by Changde and Yueyang. A summary of the main contributing dimensions and top ten contributing indicators of water security of TDLR illustrates that the effective measures to improve its water security include building embankments and sewage treatment plants through increased investment; reducing industrial water consumption; improving the ability to convert rainwater to water resources and surface water storage capacity. Additional measures, such as strengthening the integrated management of the Dongting Lake and increasing the use of reclaimed water for ecological replenishment, can effectively improve its water security. This study objectively assesses and summarizes the water security of TDLR and provides a valuable reference for relevant authorities in regional water resources planning and management, as well as for water security assessments of other similar lake regions.

Study on the ground mechanics index of deep soft foundation sections in the Dongting Lake region

Due to its special geographical location, the Dongting Lake Plain has formed a unique Dongting Lake phase deep soft ground layer. In order to investigate its stratigraphic mechanical index, a research was carried out using pile foundation static load test and pile body stress test based on a trans-Dongting Lake high speed project. The results of the study show that the ultimate bearing capacity of the test piles in this project is greater than the ultimate bearing capacity of the piles proposed by the design, and the reasons for this deviation according to the pile stress test are mainly due to the clay layer, silty powder clay layer and the side friction resistance of the fine gravel layer at the end of the pile are significantly greater than the recommended value of the ground investigation data, while the side friction resistance of the fine sand layer, powder fine sand layer and gravel sand layer is basically the same as the recommended value of the ground investigation data, This can be used as a reference for similar projects in the future.

Diagnostic efficacy of indirect haemagglutination assay for detection of Schistosoma japonicum infections among boatmen and fishermen in the Dongting Lake region

To evaluate the diagnostic efficacy of indirect haemagglutination assay (IHA) for detection of Schistosoma japonicum infections among boatmen and fishermen in Dongting Lake region, so as to provide insights into improving the schistosomiasis surveillance program among boatmen and fishermen. The boatmen and fishermen were detected for S. japonicum infections using IHA and Kato-Katz technique or miracidium hatching test nylon gauze simultaneously at schistosomiasis testing sites in the anchor sites for boatmen and fishermen in the Dongting Lake region during the period from 2014 to 2016, and using IHA for serological screening followed by parasitological testing of seropositives during the period from 2017 to 2019. The sensitivity and specificity of IHA were evaluated for detection of S. japonicum infections among boatmen and fishermen, with the 2014-2016 parasitological testing results as a gold standard. In addition, the seroprevalence of S. japonicum infections was compared among boatmen and fishermen with different characteristics and among years. A total of 306 schistosomiasis testing sites were assigned for boatmen and fishermen, and a total of 143 360 person-time boatmen and fishermen were tested for S. japonicum infections in the Dongting Lake region from 2014 to 2019. The sensitivity and specificity of IHA were 69.9%, 97.3% and 96.1% (χ2 = 74.6, P < 0.05), and 70.9%, 74.5% and 71.9% for detection of S. japonicum infections from 2014 to 2016 (χ2 = 29.4, P < 0.05), respectively. The seroprevalence of S. japonicum infections reduced from 30.3% in 2014 to 1.8% in 2019 among boatmen and fishermen, appearing an overall tendency towards a decline (Z = 1 552.4, P < 0.05). In addition, male, individuals at ages of 45 to 60 years, full-time boatmen and fishermen were more likely to be seropositive for S. japonicum infections (all P values < 0.05). The seroprevalence of S. japonicum infections appeared a tendency towards a decline among boatmen and fishermen in the Dongting Lake region year by year from 2014 to 2019. IHA presented a high efficacy for screening of S. japonicum infections among boatmen and fishermen in the Dongting Lake region.

Spatiotemporal heterogeneity of schistosomiasis in mainland China: Evidence from a multi-stage continuous downscaling sentinel monitoring

Objective: To determine the spatiotemporal distribution of Schistosoma (S.) japonicum infections in humans, livestock, and Oncomelania (O.) hupensis across the endemic foci of China.Methods: Based on multi-stage continuous downscaling of sentinel monitoring, county-based schistosomiasis surveillance data were captured from the national schistosomiasis surveillance sites of China from 2005 to 2019. The data included S. japonicum infections in humans, livestock, and O. hupensis. The spatiotemporal trends for schistosomiasis were detected using a Joinpoint regression model, with a standard deviational ellipse (SDE) tool, which determined the central tendency and dispersion in the spatial distribution of schistosomiasis. Further, more spatiotemporal clusters of S. japonicum infections in humans, livestock, and O. hupensis were evaluated by the Poisson model.Results: The prevalence of S. japonicum human infections decreased from 2.06% to zero based on data of the national schistosomiasis surveillance sites of China from 2005 to 2019, with a reduction from 9.42% to zero for the prevalence of S. japonicum infections in livestock, and from 0.26% to zero for the prevalence of S. japonicum infections in O. hupensis. Analysis using an SDE tool showed that schistosomiasis-affected regions were reduced yearly from 2005 to 2014 in the endemic provinces of Hunan, Hubei, Jiangxi, and Anhui, as well as in the Poyang and Dongting Lake regions. Poisson model revealed 11 clusters of S. japonicum human infections, six clusters of S. japonicum infections in livestock, and nine clusters of S. japonicum infections in O. hupensis. The clusters of human infection were highly consistent with clusters of S. japonicum infections in livestock and O. hupensis. They were in the 5 provinces of Hunan, Hubei, Jiangxi, Anhui, and Jiangsu, as well as along the middle and lower reaches of the Yangtze River. Humans, livestock, and O. hupensis infections with S. japonicum were mainly concentrated in the north of the Hunan Province, south of the Hubei Province, north of the Jiangxi Province, and southwestern portion of Anhui Province. In the 2 mountainous provinces of Sichuan and Yunnan, human, livestock, and O. hupensis infections with S. japonicum were mainly concentrated in the northwestern portion of the Yunnan Province, the Daliangshan area in the south of Sichuan Province, and the hilly regions in the middle of Sichuan Province.Conclusions: A remarkable decline in the disease prevalence of S. japonicum infection was observed in endemic schistosomiasis in China between 2005 and 2019. However, there remains a long-term risk of transmission in local areas, with the highest-risk areas primarily in Poyang Lake and Dongting Lake regions, requiring to focus on vigilance against the rebound of the epidemic. Development of high-sensitivity detection methods and integrating the transmission links such as human and livestock infection, wild animal infection, and O. hupensis into the surveillance-response system will ensure the elimination of schistosomiasis in China by 2030.