Advances in the study of the interaction between schistosome infections and the host's intestinal microorganisms

Schistosomiasis, also called bilharziasis, is a neglected tropical disease induced by schistosomes that infects hundreds of millions of people worldwide. In the life cycle of schistosomiasis, eggs are regarded as the main pathogenic factor, causing granuloma formation in the tissues and organs of hosts, which can cause severe gastrointestinal and liver granulomatous immune responses and irreversible fibrosis. Increasing evidence suggests that the gut microbiome influences the progression of schistosomiasis and plays a central role in liver disease via the gut-liver axis. When used as pharmaceutical supplements or adjunctive therapy, probiotics have shown promising results in preventing, mitigating, and even treating schistosomiasis. This review elucidates the potential mechanisms of this three-way parasite-host-microbiome interaction by summarizing schistosome-mediated intestinal flora disorders, local immune changes, and host metabolic changes, and elaborates the important role of the gut microbiome in liver disease after schistosome infection through the gut-liver axis. Understanding the mechanisms behind this interaction may aid in the discovery of probiotics as novel therapeutic targets and sustainable control strategies for schistosomiasis.

Knowledge, attitudes, and practices regarding schistosomiasis infection and prevention: A mixed-methods study among endemic communities of western Uganda

INTRODUCTION

In Uganda, schistosomiasis (re)infections have continued to remain high despite the implementation of mass drug administration and sensitization campaigns aimed at controlling the disease. This could imply that there are some barriers to the implemented preventive measures. We conducted a mixed-methods study in Kagadi and Ntoroko districts around Lake Albert to assess knowledge, attitudes, and practices regarding schistosomiasis and to explore and understand perspectives regarding the disease.

MATERIALS AND METHODS

Semi-structured survey questionnaires were administered to 337 household adults selected through systematic random sampling. We also interviewed 12 participants and held 28 focus-group discussion sessions with 251 individuals respectively. Quantitative data was analysed using frequencies, percentages, and chi-square tests for associations, while themes and sub-themes were used to analyse qualitative data respectively.

FINDINGS

A total of 98.5%, 81.3%, and 78.5% had heard about schistosomiasis, and knew the main transmission modes and symptoms, respectively. The majority (75.8%) said avoiding contact with water was a preventative way, while 67.5% said observing signs and symptoms was a form of diagnosis. Furthermore, 98.4% and 73.4% said it was important to defecate in latrines and to avoid contact with contaminated water respectively. However, it is difficult to avoid contact with lake water because it is the only source of livelihood, especially for fisher communities. Open defecation is commonly practiced along the lake due to insufficient space and difficulties in the construction of latrines. Myths and misconceptions reported include; lake water is safe, gassing in water causes transmission, fetching water early in the morning and from deep water is safe, and feces in the lake water act as a bait for catching fish.

CONCLUSIONS AND RECOMMENDATIONS

Despite adequate knowledge of schistosomiasis and a positive attitude towards its prevention, existing myths and misconceptions, coupled with persistent risky water, sanitation, and hygiene practices still pose a challenge. A more robust community-based awareness intervention using bottom-up participatory approaches, accompanied by the provision of clean and safe water sources and increasing latrine coverage, could provide lasting solutions to these barriers.

TIPS and splenorenal shunt for complications of portal hypertension in chronic hepatosplenic schistosomiasis-A case series and review of the literature

Background

Transjugular intrahepatic portosystemic shunt (TIPS) and shunt surgery are established treatment options for portal hypertension, but have not been systematically evaluated in patients with portal hypertension due to hepatosplenic schistosomiasis (HSS), one of the neglected tropical diseases with major impact on morbidity and mortality in endemic areas.

Methods

In this retrospective case study, patients with chronic portal hypertension due to schistosomiasis treated with those therapeutic approaches in four tertiary referral hospitals in Germany and Italy between 2012 and 2020 were included. We have summarized pre-interventional clinical data, indication, technical aspects of the interventions and clinical outcome.

Findings

Overall, 13 patients with confirmed HSS were included. 11 patients received TIPS for primary or secondary prophylaxis of variceal bleeding due to advanced portal hypertension and failure of conservative management. In two patients with contraindications for TIPS or technically unsuccessful TIPS procedure, proximal splenorenal shunt surgery in combination with splenectomy was conducted. During follow-up (mean follow-up 23 months, cumulative follow-up time 31 patient years) no bleeding events were documented. In five patients, moderate and transient episodes of overt hepatic encephalopathy were observed. In one patient each, liver failure, portal vein thrombosis and catheter associated sepsis occurred after TIPS insertion. All complications were well manageable and had favorable outcomes.

Conclusions

TIPS implantation and shunt surgery are safe and effective treatment options for patients with advanced HSS and sequelae of portal hypertension in experienced centers, but require careful patient selection.

Hepatosplenic schistosomiasis is a severe form of chronic infection with various trematodes of the genus Schistosoma, characterized by portal venous fibrosis, splenomegaly with hypersplenism, and portal hypertension with subsequent life-threatening bleeding events. While effective anthelminthic treatment is available, portal fibrosis is only partially reversible. Portal hypertension with subsequent bleeding events as a complication is hitherto insufficiently addressed. Surgical techniques are currently the best established treatment option for HSS, despite their inherent complication risk and irreversibility. Interventional procedures like TIPS have rarely been assessed in HSS with mixed results. In a series of 13 cases with follow-up periods up to 99 months and a cumulative follow-up of 30.9 years, we demonstrate excellent bleeding prophylaxis and a low adverse event rate of TIPS and–if TIPS proves infeasible–splenorenal shunt surgery. Main complications of TIPS comprise transient hepatic encephalopathy and increase of liver enzymes, especially in patients with hepatic comorbidities. Due to necessary infrastructure and skills, TIPS implantation is currently limited to specialized centers. However, we think that our study can support the establishment and development of new treatment options for schistosomiasis and, in the medium term, also improve the prognosis of this neglected tropical disease in endemic regions.

Prevalence and distribution of schistosomiasis in human, livestock, and snail populations in northern Senegal: a One Health epidemiological study of a multi-host system

BACKGROUND

Schistosomiasis is a neglected tropical disease of global medical and veterinary importance. As efforts to eliminate schistosomiasis as a public health problem and interrupt transmission gather momentum, the potential zoonotic risk posed by livestock Schistosoma species via viable hybridisation in sub-Saharan Africa have been largely overlooked. We aimed to investigate the prevalence, distribution, and multi-host, multiparasite transmission cycle of Haematobium group schistosomiasis in Senegal, West Africa.

METHODS

In this epidemiological study, we carried out systematic surveys in definitive hosts (humans, cattle, sheep, and goats) and snail intermediate hosts, in 2016-18, in two areas of Northern Senegal: Richard Toll and Lac de Guiers, where transmission is perennial; and Barkedji and Linguère, where transmission is seasonal. The occurrence and distribution of Schistosoma species and hybrids were assessed by molecular analyses of parasitological specimens obtained from the different hosts. Children in the study villages aged 5-17 years and enrolled in school were selected from school registers. Adults (aged 18-78 years) were self-selecting volunteers. Livestock from the study villages in both areas were also randomly sampled, as were post-mortem samples from local abattoirs. Additionally, five malacological surveys of snail intermediate hosts were carried out at each site in open water sources used by the communities and their animals.

FINDINGS

In May to August, 2016, we surveyed 375 children and 20 adults from Richard Toll and Lac de Guiers, and 201 children and 107 adults from Barkedji and Linguère; in October, 2017, to January, 2018, we surveyed 386 children and 88 adults from Richard Toll and Lac de Guiers, and 323 children and 85 adults from Barkedji and Linguère. In Richard Toll and Lac de Guiers the prevalence of urogenital schistosomiasis in children was estimated to be 87% (95% CI 80-95) in 2016 and 88% (82-95) in 2017-18. An estimated 63% (in 2016) and 72% (in 2017-18) of infected children were shedding Schistosoma haematobium-Schistosoma bovis hybrids. In adults in Richard Toll and Lac de Guiers, the prevalence of urogenital schistosomiasis was estimated to be 79% (52-97) in 2016 and 41% (30-54) in 2017-18, with 88% of infected samples containing S haematobium-S bovis hybrids. In Barkedji and Linguère the prevalence of urogenital schistosomiasis in children was estimated to be 30% (23-38) in 2016 and 42% (35-49) in 2017-18, with the proportion of infected children found to be shedding S haematobium-S bovis hybrid miracidia much lower than in Richard Toll and Lac de Guiers (11% in 2016 and 9% in 2017-18). In adults in Barkedji and Linguère, the prevalence of urogenital schistosomiasis was estimated to be 26% (17-36) in 2016 and 47% (34-60) in 2017-18, with 10% of infected samples containing S haematobium-S bovis hybrids. The prevalence of S bovis in the sympatric cattle population of Richard Toll and the Lac de Guiers was 92% (80-99), with S bovis also found in sheep (estimated prevalence 14% [5-31]) and goats (15% [5-33]). In Barkedji and Linguère the main schistosome species in livestock was Schistosoma curassoni, with an estimated prevalence of 73% (48-93) in sheep, 84% (61-98) in goats and 8% (2-24) in cattle. S haematobium-S bovis hybrids were not found in livestock. In Richard Toll and Lac de Guiers 35% of infected Bulinus spp snail intermediate hosts were found to be shedding S haematobium-S bovis hybrids (68% shedding S haematobium; 17% shedding S bovis); however, no snails were found to be shedding S haematobium hybrids in Barkedji and Linguère (29% shedding S haematobium; 71% shedding S curassoni).

INTERPRETATION

Our findings suggest that hybrids originate in humans via zoonotic spillover from livestock populations, where schistosomiasis is co-endemic. Introgressive hybridisation, evolving host ranges, and wider ecosystem contexts could affect the transmission dynamics of schistosomiasis and other pathogens, demonstrating the need to consider control measures within a One Health framework.

FUNDING

Zoonoses and Emerging Livestock Systems programme (UK Biotechnology and Biological Sciences Research Council, UK Department for International Development, UK Economic and Social Research Council, UK Medical Research Council, UK Natural Environment Research Council, and UK Defence Science and Technology Laboratory).

Schistosome TRP channels: An appraisal

Ion channels underlie electrical excitability in cells and are essential for a variety of functions, most notably neuromuscular and sensory activity. They are also validated targets for a preponderance of approved anthelmintic compounds. Transient receptor potential (TRP) channels constitute an ion channel superfamily whose members play important roles in sensory signaling, regulation of ion homeostasis, organellar trafficking, and other key cellular and organismal activities. Unlike most other ion channels, TRP channels are often polymodal, gated by a variety of mechanisms. Furthermore, TRP channels fall into several classes or subtypes based on sequence and structure. Until recently, there had been very little investigation of the properties and functions of TRP channels from parasitic helminths, including schistosomes, but that situation has changed in the past few years. Indeed, it is now clear that at least some schistosome TRP channels exhibit unusual pharmacological properties, and, intriguingly, both a mammalian and a schistosome TRP channel are activated by praziquantel, the current antischistosomal drug of choice. With the latest release of the Schistosoma mansoni genome database, several changes in predicted TRP channel sequences appeared, some of which were significant. This review updates and reassesses the TRP channel repertoire in S. mansoni, examines recent findings regarding these potential therapeutic targets, and provides guideposts for some of the physiological functions that may be mediated by these channels in schistosomes.

Aquatic macrophytes and macroinvertebrate predators affect densities of snail hosts and local production of schistosome cercariae that cause human schistosomiasis

Background

Schistosomiasis is responsible for the second highest burden of disease among neglected tropical diseases globally, with over 90 percent of cases occurring in African regions where drugs to treat the disease are only sporadically available. Additionally, human re-infection after treatment can be a problem where there are high numbers of infected snails in the environment. Recent experiments indicate that aquatic factors, including plants, nutrients, or predators, can influence snail abundance and parasite production within infected snails, both components of human risk. This study investigated how snail host abundance and release of cercariae (the free swimming stage infective to humans) varies at water access sites in an endemic region in Senegal, a setting where human schistosomiasis prevalence is among the highest globally.

Methods/Principal findings

We collected snail intermediate hosts at 15 random points stratified by three habitat types at 36 water access sites, and counted cercarial production by each snail after transfer to the laboratory on the same day. We found that aquatic vegetation was positively associated with per-capita cercarial release by snails, probably because macrophytes harbor periphyton resources that snails feed upon, and well-fed snails tend to produce more parasites. In contrast, the abundance of aquatic macroinvertebrate snail predators was negatively associated with per-capita cercarial release by snails, probably because of several potential sublethal effects on snails or snail infection, despite a positive association between snail predators and total snail numbers at a site, possibly due to shared habitat usage or prey tracking by the predators. Thus, complex bottom-up and top-down ecological effects in this region plausibly influence the snail shedding rate and thus, total local density of schistosome cercariae.

Conclusions/Significance

Our study suggests that aquatic macrophytes and snail predators can influence per-capita cercarial production and total abundance of snails. Thus, snail control efforts might benefit by targeting specific snail habitats where parasite production is greatest. In conclusion, a better understanding of top-down and bottom-up ecological factors that regulate densities of cercarial release by snails, rather than solely snail densities or snail infection prevalence, might facilitate improved schistosomiasis control.

Over 800 million people are at risk of schistosomiasis and environmental factors that regulate densities of cercariae parasites that infect humans remain poorly understood. We sampled a spatially extensive area at 36 water-access points in northern Senegal, and quantified densities of snail intermediate hosts, snail predators, and aquatic vegetation in each sample, as well as cercariae released from snails after they were brought to the laboratory. We found that the quantity of submerged aquatic vegetation, particularly Ceratophyllum spp., was positively associated with schistosome cercariae released per infected snail, and total potential cercariae released by the collected snails per water access site. In contrast, the abundance of aquatic predators near infected snails (in the same sweep) was negatively associated with the per-capita cercarial release by infected snails, but positively associated with total snail abundance per site. Additionally, snail densities and potential cercarial densities (estimated as the sum of cercariae released by all collected, infected snails at a site) were only weakly correlated, suggesting that snail densities alone might not accurately reflect total potential of those snails to emit schistosome cercariae. Overall, a better understanding of aquatic factors that can influence the production of schistosome cercariae under field conditions, rather than snail host abundance alone, might facilitate improvements in schistosomiasis monitoring and control.

Effects of agrochemical pollution on schistosomiasis transmission: a systematic review and modelling analysis

BACKGROUND

Agrochemical pollution of surface waters is a growing global environmental challenge, especially in areas where agriculture is rapidly expanding and intensifying. Agrochemicals might affect schistosomiasis transmission through direct and indirect effects on Schistosoma parasites, their intermediate snail hosts, snail predators, and snail algal resources. We aimed to review and summarise the effects of these agrochemicals on schistosomiasis transmission dynamics.

METHODS

We did a systematic review of agrochemical effects on the lifecycle of Schistosoma spp and fitted dose-response models to data regarding the association between components of the lifecycle and agrochemical concentrations. We incorporated these dose-response functions and environmentally relevant concentrations of agrochemicals into a mathematical model to estimate agrochemical effects on schistosomiasis transmission. Dose-response functions were used to estimate individual agrochemical effects on estimates of the agrochemically influenced basic reproduction number, R0, for Schistosoma haematobium. We incorporated time series of environmentally relevant agrochemical concentrations into the model and simulated mass drug administration control efforts in the presence of agrochemicals.

FINDINGS

We derived 120 dose-response functions describing the effects of agrochemicals on schistosome lifecycle components. The median estimate of the basic reproduction number under agrochemical-free conditions, was 1·65 (IQR 1·47-1·79). Agrochemical effects on estimates of R0 for S haematobium ranged from a median three-times increase (R0 5·05, IQR 4·06-5·97) to transmission elimination (R0 0). Simulations of transmission dynamics subject to interacting annual mass drug administration and agrochemical pollution yielded a median estimate of 64·82 disability-adjusted life-years (DALYs) lost per 100 000 people per year (IQR 62·52-67·68) attributable to atrazine use. In areas where aquatic arthropod predators of intermediate host snails suppress transmission, the insecticides chlorpyrifos (6·82 DALYs lost per 100 000 people per year, IQR 4·13-8·69) and profenofos (103·06 DALYs lost per 100 000 people per year, IQR 89·63-104·90) might also increase the disability burden through their toxic effects on arthropods.

INTERPRETATION

Expected environmental concentrations of agrochemicals alter schistosomiasis transmission through direct and indirect effects on intermediate host and parasite densities. As industrial agricultural practices expand in areas where schistosomiasis is endemic, strategies to prevent increases in transmission due to agrochemical pollution should be developed and pursued.

FUNDING

National Science Foundation, National Institutes of Health.

Current and Novel Therapies Against Helminthic Infections: The Potential of Antioxidants Combined with Drugs

Infections caused by Schistosoma haematobium and Opisthorchisviverrini are classified as Group 1 biological carcinogen and it has been postulated that parasites produce oxysterol and estrogen-like metabolites that might be considered as initiators of infection-associated carcinogenesis. Chemotherapy for these helminthic infections relies on a single drug, praziquantel, (PZQ) that mainly targets the parasite. Additionally, PZQ has some major drawbacks as inefficacy against juvenile form and alone it is not capable to counteract pathologies associated to infections or prevent carcinogenesis. There is an urgent need to develop novel therapeutic approaches that not only target the parasite but also improve the pathologies associated to infection, and ultimately, counteract or/and prevent the carcinogenesis processes. Repurposing the drug in combination of compounds with different modes of action is a promising strategy to find novel therapeutics approaches against these helminthic infections and its pathologies. Here, we emphasized that using antioxidants either alone or combined with anthelmintic drugs could ameliorate tissue damage, infection-associated complications, moreover, could prevent the development of cancer associated to infections. Hence, antioxidants represent a potential adjuvant approach during treatment to reduce morbidity and mortality. Despite the success of some strategies, there is a long way to go to implement novel therapies for schistosomiasis.

[Endemic situation of schistosomiasis in Wuhu City from 2009 to 2018]

OBJECTIVE

To analyze the endemic situation of schistosomiasis in Wuhu City from 2009 to 2018, so as to provide evidence for adjusting and developing the control strategy.

METHODS

The data regarding the endemic situation were retrospectively collected and analyzed in Wuhu City from 2009 to 2018.

RESULTS

The prevalence of human Schistosoma japonicum infections reduced from 0.450% in 2009 to 0.035% in 2018 in Wuhu City, and a reduction rate of 92.22% (χ² = 1 6128.307, P < 0.01), and the prevalence of S. japonicum infections decreased from 0.483% in 2009 to 0 in 2018 (χ² = 27.570, P < 0.01) in livestock. The area of snail habitats increased from 1 501.07 hm² in 2009 to 4 408.62 hm² in 2018, with an increase of 193.70%. No infected snails were found in Wuhu City since 2012, and no egg positives were detected in humans and livestock since 2016.

CONCLUSIONS

Currently, the endemic situation of schistosomiasis is at a low level in Wuhu City; however, there are still factors affecting schistosomiasis transmission. In the future, the integrated strategy with emphasis on the control of infectious source and the surveillance-response system should be intensified to consolidate the achievements of schistosomiasis control.

[Endemic situation of schistosomiasis in Jiangshan City from 2008 to 2018]

OBJECTIVE

To analyze the endemic situation of schistosomiasis in Jiangshan City from 2008 to 2018, so as to provide evidence for formulating the future control strategy.

METHODS

The data regarding Oncomelania snail survey and control, schistosomiasis examinations and environmental improvements were collected in Jiangshan City from 2008 to 2018. The changes in snail status and morbidity due to Schistosoma japonicum infections were analyzed to assess the effectiveness of comprehensive schistosomiasis control.

RESULTS

From 2008 to 2018, a total of 61 220 person-times were examined for S. japonicum infections in Jiangshan City, and the overall seroprevalence of S. japonicum infections was 0.56% (343/61 220); however, no egg-positives were detected. Among 4 231 cattle screened for S. japonicum infections using blood tests in Jiangshan City during the period from 2008 to 2018, 12 were sero-positive, with sero-prevalence of 0.28% (12/4 231), and no egg-positives were identified. There were 422 snail habitats identified in Jiangshan City during the study period, covering an area of 46.915 hm², and among the 31 686 snails dissected, no S. japonicum infections were detected. An area of 3 625.492 hm² snail habitats were subjected to repeated snail control and 11 settings were given environmental improvements, covering snail habitats of 17.880 hm² and historical snail habitats of 204.380 hm².

CONCLUSIONS

Following the implementation of environmental improvements-based comprehensive schistosomiasis control, the endemic situation of schistosomiasis is stable in Jiangshan City; however, there is still a risk of snail importation and re-emerging schistosomiasis. Therefore, the monitoring of snails and morbidity due to S. japonicum infections should be intensified in the city.

Unavoidable Risks: Local Perspectives on Water Contact Behavior and Implications for Schistosomiasis Control in an Agricultural Region of Northern Senegal

Human schistosomiasis is a snail-borne parasitic disease affecting more than 200 million people worldwide. Direct contact with snail-infested freshwater is the primary route of exposure. Water management infrastructure, including dams and irrigation schemes, expands snail habitat, increasing the risk across the landscape. The Diama Dam, built on the lower basin of the Senegal River to prevent saltwater intrusion and promote year-round agriculture in the drought-prone Sahel, is a paradigmatic case. Since dam completion in 1986, the rural population-whose livelihoods rely mostly on agriculture-has suffered high rates of schistosome infection. The region remains one of the most hyperendemic regions in the world. Because of the convergence between livelihoods and environmental conditions favorable to transmission, schistosomiasis is considered an illustrative case of a disease-driven poverty trap (DDPT). The literature to date on the topic, however, remains largely theoretical. With qualitative data generated from 12 focus groups in four villages, we conducted team-based theme analysis to investigate how perception of schistosomiasis risk and reported preventive behaviors may suggest the presence of a DDPT. Our analysis reveals three key findings: 1) rural villagers understand schistosomiasis risk (i.e., where and when infections occur), 2) accordingly, they adopt some preventive behaviors, but ultimately, 3) exposure persists, because of circumstances characteristic of rural livelihoods. These findings highlight the capacity of local populations to participate actively in schistosomiasis control programs and the limitations of widespread drug treatment campaigns. Interventions that target the environmental reservoir of disease may provide opportunities to reduce exposure while maintaining resource-dependent livelihoods.

[Design of schistosomiasis surveillance sites based on Spatial Kluster Analysis by Tree Edge Removal (SKATER) method: an exploratory study]

OBJECTIVE

To develop a method for designing schistosomiasis surveillance sites, so as to improve the efficiency and quality of schitsosomiasis surveillance.

METHODS

By using the minimum spanning tree-based Spatial Kluster Analysis by Tree Edge Removal (SKATER) method, spatially constrained clustering was performed upon 31 historical schistosomiasis-endemic counties (districts) in Anhui Province. A surveillance site was selected from each cluster to evaluate the representativeness and surveillance efficiency of these cluster-based surveillance sites for the endemic situation of schistosomiassi in Anhui Province, and to compare the surveillance efficiency with local national schistosomiasis surveillance sites.

RESULTS

There was no significant difference in the environmental factors between the cluster-based schistosomiasis surveillance sites and the whole region, showing a high homogeneity. If the same number of schistosomiasis surveillance sites was selected, there was no significant difference between the cluster-based surveillance sites and national schistosomiasis surveillance sites in the efficiency of the mean risk and long-term trend of schistosomiasis surveillance in Anhui Province; however, the cluster-based surveillance sites were superior to the national schistosomiasis surveillance sites for the prediction and estimation of the endemic situation of schistosomiasis in the unmonitored areas.

CONCLUSIONS

The SKATER-based selection of schistosomiasis surveillance sites may better represent the endemic situation of schistosomiasis in Anhui Province, which may serve as an effective supplement for the conventional method of selecting schistosomiasis surveillance sites.

[Strategy of schistosomiasis elimination and its effects in Jinhu County, Jiangsu Province]

OBJECTIVE

To understand the strategy of schistosomiasis elimination and its effects in Jinhu County, Jiangsu Province.

METHODS

The data of schistosomiasis control in Jinhu County at different stages from 1970 to 2017 were collected and analyzed.

RESULTS

From 1970 to 2017, there were three stages of schistosomiasis control, including transmission control, transmission interruption, and monitoring and elimination stages in Jinhu County. The main measures included Oncomelania hupensis snail control, infectious source control, and health education. A total of area of 290 691.78 hm² was detected in Jinhu County, and the area with snails was 3 420.98 hm². There were 8 729.37 hm² area with snails was controlled. Since 2014, no O. hupensis snails were found. A total of 525 377 person-times were examined for schistosomiasis, with 2 815 schistosomiasis patients identified, and 2 844 person-times were treated by chemotherapy. In addition, 977 cases received the expand chemotherapy. Since 1990, no local schistosome-infected persons were found. In 2017, the awareness rate of schistosomiasis control knowledge and the correct rate of health behavior were increased by 54.59% and 14.23% respectively compared with those in 1992.

CONCLUSIONS

The comprehensive schistosomiasis control measures implemented in Jinhu County at different periods have achieved remarkable outputs and accelerated the schistosomiasis elimination process. However, the precise control measures should be implemented in the future to consolidate the prevention and control achievements.

[Surveillance of schistosomiasis in a national surveillance site of Jurong City, 2015-2017]

OBJECTIVE

To understand the endemic situation and control effect of schistosomiasis through the surveillance in a national surveillance site of Jurong City, so as to provide the evidence for formulating the prevention and control measures.

METHODS

According to the National Schistosomiasis Monitoring Scheme (2014 Edition), the surveillance of schistosome infection in Oncomelania hupensis snails, residents and livestock was performed in the Kongqing Village, a national surveillance site of Jurong City, from 2015 to 2017.

RESULTS

The areas with snails were 0, 0, and 0.63 hm² in 2015, 2016, and 2017 respectively; the average densities of living snails were 0, 0, and 0.19 snails/0.1 m² in 2015, 2016, and 2017 respectively. No schistosome-infected snails were found. The positive rates of blood tests for schistosomiasis in the local residents were 7.72%, 7.45% and 3.45%, and the positive rates of blood tests in the floating population were 4.90%, 3.47% and 0.97% in 2015, 2016 and 2017, respectively. No positives were found in the schistosome etiology detection in the crowd and livestock.

CONCLUSIONS

The effect of schistosomiasis prevention and control is obvious in Jurong City, but O. hupensis snails are still of recurrence. Therefore, the monitoring and control efforts should be strengthened to consolidate the achievements of schistosomiasis prevention and control.

Molecular characterisation of immunological memory following homologous or heterologous challenges in the schistosomiasis vector snail, Biomphalaria glabrata

Invertebrate immune response may be primed by a current infection in a sustained manner, leading to the failure of a secondary infection with the same pathogen. The present study focuses on the Schistosomiasis vector snail Biomphalaria glabrata, in which a specific genotype-dependent immunological memory was demonstrated as a shift from a cellular to a humoral immune response. Herein, we investigate the complex molecular bases associated with this genotype-dependant immunological memory response. We demonstrate that Biomphalaria regulates a polymorphic set of immune recognition molecules and immune effector repertoires to respond to different strains of Schistosoma parasites. These results suggest a combinatorial usage of pathogen recognition receptors (PRRs) that distinguish different strains of parasites during the acquisition of immunological memory. Immunizations also show that snails become resistant after exposure to parasite extracts. Hemolymph transfer and a label-free proteomic analysis proved that circulating hemolymph compounds can be produced and released to more efficiently kill the newly encountered parasite of the same genetic lineage.

Schistosomiasis in Malaysia: A review

Schistosomiasis, a neglected tropical parasitic disease caused by the trematode flatworms of the genus Schistosoma, affects approximately 207 million people worldwide. Among the five main species infecting humans, Schistosoma mansoni and S. japonicum are responsible for the majority of hepatointestinal schistosomiasis. Human settlements near fresh water sites that lack proper sanitary systems often contribute to the transmission of disease. This risk particularly impacts on travellers or immigrants who come into contact with larvae-contaminated water. This review discusses the central features of schistosomiasis; including clinical manifestations, diagnosis, treatments, and the preventive measures available for the control of this disease. The description of the Malaysian schistosome species Schistosoma malayensis and the current status of schistosomiasis in Malaysia including the compilation of cases diagnosed from 1904 to 2015 are also discussed in this paper.

Estimating the elimination feasibility in the 'end game' of control efforts for parasites subjected to regular mass drug administration: Methods and their application to schistosomiasis

Progress towards controlling and eliminating parasitic worms, including schistosomiasis, onchocerciasis, and lymphatic filariasis, is advancing rapidly as national governments, multinational NGOs, and pharmaceutical companies launch collaborative chemotherapeutic control campaigns. Critical questions remain regarding the potential for achieving elimination of these infections, and analytical methods can help to quickly estimate progress towards-and the probability of achieving-elimination over specific timeframes. Here, we propose the effective reproduction number, Reff, as a proxy of elimination potential for sexually reproducing worms that are subject to poor mating success at very low abundance (positive density dependence, or Allee effects). Reff is the number of parasites produced by a single reproductive parasite at a given stage in the transmission cycle, over the parasite's lifetime-it is the generalized form of the more familiar basic reproduction number, R0, which only applies at the beginning of an epidemic-and it can be estimated in a 'model-free' manner by an estimator ('ε'). We introduce ε, demonstrate its estimation using simulated data, and discuss how it may be used in planning and evaluation of ongoing elimination efforts for a range of parasitic diseases.

Impact of schistosome infection on long-term HIV/AIDS outcomes

Background

Africa bears the burden of approximately 70% of global HIV infections and 90% of global schistosome infections. We sought to investigate the impact of schistosome infection at the time of HIV-1 seroconversion on the speed of HIV-1 disease progression, as measured by the outcome CD4+ T-cell (CD4) counts <350 cells/μL and/or death. We hypothesized that people who had been infected with Schistosoma spp. at the time they acquired HIV-1 infection would have impaired antiviral immune response, thus leading them to progress twice as fast to a CD4 count less than 350 cells/μL or death than would people who had been free of schistosomes at time of HIV-1 seroconversion.

Methods and principal findings

We conducted a longitudinal study in Tanzania from 2006 to 2017 using stored blood spot samples, demographic surveillance and sero-survey data from the community, and a review of clinical charts. A competing risk analysis was performed to look at the difference in time to reaching CD4 counts < 350 cells/μL and/or death in HIV-1-infected people who were infected versus not infected with Schistosoma spp. at time of HIV-1 seroconversion. We found an 82% reduction in risk of reaching the outcome in seroconverters who had been infected with Schistosoma (subHazard Ratio = 0.18[0.068,0.50], p = 0.001) after adjusting for age, occupation, clinic attendance and time-dependent covariates.

Conclusions

Our study demonstrates that people with schistosome infection at the time of HIV-seroconversion develop adverse HIV outcomes more slowly than those without. The findings are contrary to our original hypothesis. Our current longitudinal findings suggest complex interactions between HIV-1 and schistosome co-infections that may be modulated over time. We urge new immunological studies to investigate the long-term impact of schistosome infection on HIV-1 viral load and CD4 counts as well as related immunologic pathways.

Several studies had shown that people infected with schistosome parasites were at risk of getting HIV and that they may have higher HIV viral concentrations in their blood as well. The authors explored the impact of the parasite on HIV disease after infection, expecting that people co-infected with the parasite at time of HIV-infection would develop worse HIV outcomes than people who did not have the parasite. HIV seroconverters were identified among a large cohort tested regularly for HIV in northwest Tanzania and were followed-up in clinics to determine their CD4 + T-cells counts and mortality. The seroconverters’ stored blood samples were tested for infection with the parasite and outcomes were compared between seroconverters who were and were not infected with the parasites at the time that they became HIV-infected. The authors surprisingly found that people with the parasite experienced fewer negative outcomes of HIV than people who did not have the parasite. To the investigators’ knowledge, this is the first longitudinal study to find this result. Long-term immunological changes may explain this protective effect and more studies are recommended to explore this research question.

The human-snail transmission environment shapes long term schistosomiasis control outcomes: Implications for improving the accuracy of predictive modeling

INTRODUCTION

Schistosomiasis is a chronic parasitic trematode disease that affects over 240 million people worldwide. The Schistosoma lifecycle is complex, involving transmission via specific intermediate-host freshwater snails. Predictive mathematical models of Schistosoma transmission have often chosen to simplify or ignore the details of environmental human-snail interaction in their analyses. Schistosome transmission models now aim to provide better precision for policy planning of elimination of transmission. This heightens the importance of including the environmental complexity of vector-pathogen interaction in order to make more accurate projections.

METHODOLOGY AND PRINCIPAL FINDINGS

We propose a nonlinear snail force of infection (FOI) that takes into account an intermediate larval stage (miracidium) and snail biology. We focused, in particular, on the effects of snail force of infection (FOI) on the impact of mass drug administration (MDA) in human communities. The proposed (modified) model was compared to a conventional model in terms of their predictions. A longitudinal dataset generated in Kenya field studies was used for model calibration and validation. For each sample community, we calibrated modified and conventional model systems, then used them to model outcomes for a range of MDA regimens. In most cases, the modified model predicted more vigorous post-MDA rebound, with faster relapse to baseline levels of infection. The effect was pronounced in higher risk communities. When compared to observed data, only the modified system was able to successfully predict persistent rebound of Schistosoma infection.

CONCLUSION AND SIGNIFICANCE

The observed impact of varying location-specific snail inputs sheds light on the diverse MDA response patterns noted in operational research on schistosomiasis control, such as the recent SCORE project. Efficiency of human-to-snail transmission is likely to be much higher than predicted by standard models, which, in practice, will make local elimination by implementation of MDA alone highly unlikely, even over a multi-decade period.

Transcriptome sequencing and differential gene expression analysis of the schistosome-transmitting snail Oncomelania hupensis inhabiting hilly and marshland regions

The freshwater snail Oncomelania hupensis is the unique intermediate host of the blood fluke Schistosoma japonicum, which is the major cause of schistosomiasis. The snail inhabits two contrasting environments: the hilly and marshland regions. The hilly snails are smaller in size and have the typical smooth shell, whereas the marshland snails are larger and possess the ribbed shell. To reveal the differences in gene expression between the hilly and marshland snails, a total of six snails, three per environment, were individually examined by RNA sequencing technology. All paired-end reads were assembled into contigs from which 34,760 unigenes were predicted. Based on single nucleotide polymorphisms, principal component analysis and neighbor-joining clustering revealed two distinct clusters of hilly and marshland snails. Analysis of expression changes between environments showed that upregulated genes relating to immunity and development were enriched in hilly snails, while those associated with reproduction were over-represented in marshland snails. Eight differentially expressed genes between the two types of snails were validated by qRT-PCR. Our study identified candidate genes that could be targets for future functional studies, and provided a link between expression profiling and ecological adaptation of the snail that may have implications for schistosomiasis control.

Changes in the neuropeptide content of Biomphalaria ganglia nervous system following Schistosoma infection

BACKGROUND

Molluscs, including snails, are prone to parasite infection, which can lead to massive physiological and behavioural changes, yet many of the molecular components involved remain unresolved. Central to this point is the neural system that in snails consists of several ganglia that regulate the animals' physiology and behaviour patterns. The availability of a genomic resource for the freshwater snail Biomphalaria glabrata provides a mean towards the high throughput analysis of changes in the central nervous system (CNS) following infection with Schistosoma miracidia.

RESULTS

In this study, we performed a proteomic analysis of the B. glabrata CNS at pre-patent infection, providing a list of proteins that were further used within a protein-protein interaction (PPI) framework against S. mansoni proteins. A hub with most connections for both non-infected and infected Biomphalaria includes leucine aminopeptidase 2 (LAP2), which interacts with numerous miracidia proteins that together belong to the immunoglobulin family of cell adhesion related molecules. We additionally reveal the presence of at least 165 neuropeptides derived from the precursors of buccalin, enterin, FMRF, FVRI, pedal peptide 1, 2, 3 and 4, RYamide, RFamide, pleurin and others. Many of these were present at significantly reduced levels in the snail's CNS post-infection, such as the egg laying hormone, a neuropeptide required to initiate egg laying in gastropod molluscs.

CONCLUSIONS

Our analysis demonstrates that LAP2 may be a key component that regulates parasite infection physiology, as well as establishing that parasite-induced reproductive castration may be facilitated by significant reductions in reproduction-associated neuropeptides. This work helps in our understanding of molluscan neuropeptides and further stimulates advances in parasite-host interactions.

Decline in infection-related morbidities following drug-mediated reductions in the intensity of Schistosoma infection: A systematic review and meta-analysis

Background

Since 1984, WHO has endorsed drug treatment to reduce Schistosoma infection and its consequent morbidity. Cross-sectional studies suggest pre-treatment correlation between infection intensity and risk for Schistosoma-related pathology. However, evidence also suggests that post-treatment reduction in intensity may not reverse morbidity because some morbidities occur at all levels of infection, and some reflect permanent tissue damage. The aim of this project was to systematically review evidence on drug-based control of schistosomiasis and to develop a quantitative estimate of the impact of post-treatment reductions in infection intensity on prevalence of infection-associated morbidity.

Methodology/Principal findings

This review was registered at inception with PROSPERO (CRD42015026080). Studies that evaluated morbidity before and after treatment were identified by online searches and searches of private archives. Post-treatment odds ratios or standardized mean differences were calculated for each outcome, and these were correlated to treatment-related egg count reduction ratios (ERRs) by meta-regression. A greater ERR correlated with greater reduction in odds of most morbidities. Random effects meta-analysis was used to derive summary estimates: after treatment of S. mansoni and S. japonicum, left-sided hepatomegaly was reduced by 54%, right-sided hepatomegaly by 47%, splenomegaly by 37%, periportal fibrosis by 52%, diarrhea by 53%, and blood in stools by 75%. For S. haematobium, hematuria was reduced by 92%, proteinuria by 90%, bladder lesions by 86%, and upper urinary tract lesions by 72%. There were no consistent changes in portal dilation or hemoglobin levels. In sub-group analysis, age, infection status, region, parasite species, and interval to follow-up were associated with meaningful differences in outcome.

Conclusion/Significance

While there are challenges to implementing therapy for schistosomiasis, and praziquantel therapy is not fully curative, reductions in egg output are significantly correlated with decreased morbidity and can be used to project diminution in disease burden when contemplating more aggressive strategies to minimize infection intensity.

Schistosomiasis is the disease caused by infection with Schistosoma parasitic flukes. Depending on the infecting species, chronic Schistosoma infection can cause a variety of pathologies including liver and spleen enlargement, fibrosis and hypertension of the portal vein of the liver, or bladder ulceration and deformities and kidney blockage. Infection can also cause anemia, diarrhea, abdominal pain, and decreased physical fitness. In our study, we quantified the reductions in prevalence of infection-related morbidities among populations with Schistosoma infection, as achieved by giving one or more drug treatments. We systematically reviewed 71 available reports of Schistosoma-related morbidity reduction and determined, based on a meta-analysis of the primary data, that the odds of persisting morbidity progressively decrease when greater post-treatment reductions in parasite burden are achieved, as reflected by reduced egg counts in standard diagnostic testing. This suggests that repeated or more effective anti-parasite drug treatment will be a valuable tool for greater reduction of Schistosoma-related patient morbidities in affected areas.

A Genome Wide Comparison to Identify Markers to Differentiate the Sex of Larval Stages of Schistosoma haematobium, Schistosoma bovis and their Respective Hybrids

For scientists working on gonochoric organisms, determining sex can be crucial for many biological questions and experimental studies, such as crossbreeding, but it can also be a challenging task, particularly when no sexual dimorphism is visible or cannot be directly observed. In metazoan parasites of the genus Schistosoma responsible for schistosomiasis, sex is genetically determined in the zygote with a female heterogametic ZW/ZZ system. Adult flukes have a pronounced sexual dimorphism, whereas the sexes of the larval stages are morphologically indistinguishable but can be distinguished uniquely by using molecular methods. Therefore, reliable methods are needed to identify the sex of larvae individuals. Here, we present an endpoint PCR-based assay using female-specific sequences identified using a genome-wide comparative analysis between males and females. This work allowed us to identify sex-markers for Schistosoma haematobium and Schistosoma bovis but also the hybrid between both species that has recently emerged in Corsica (France). Five molecular sex-markers were identified and are female-specific in S. haematobium and the hybrid parasite, whereas three of them are also female-specific in S. bovis. These molecular markers will be useful to conduct studies, such as experimental crosses on these disease-causing blood flukes, which are still largely neglected but no longer restricted to tropical areas.

Current global changes (environmental and anthropogenic) are expected to promote the spread and transmission of infectious diseases. One of the direct consequences of such changes is the modification of the geographical distribution of species, enabling natural hybridization. Such hybridization is already known to occur in schistosomes, and offspring have been shown to have superior virulence and invasive capacities. The recent outbreak of a hybrid between the human- and animal- infecting schistosomes, S. haematobium x S. bovis, in Europe (Corsica, France) clearly demonstrates this invasive capacity and raises the risk of zoonotic transmission. Therefore, it is important to study such hybrids, and experimental crosses are critical to address this issue. Here, we developed molecular sex markers for S. haematobium and S. bovis in order to distinguish gender and to be able to generate differentially introgressed hybrids, allowing us to investigate parasite fitness.

Universal Stress Proteins as New Targets for Environmental and Therapeutic Interventions of Schistosomiasis

In spite of various control measures and eradication methods that have been in progress, schistosomiasis still prevails as one of the most prevalent debilitating parasitic diseases, typically affecting the poor and the underprivileged that are predominantly concentrated in sub-Saharan Africa. The parasitic schistosome blood fluke responsible for causing the disease completes its complex developmental cycle in two hosts: humans and freshwater snails, where they physically undergo gross modifications to endure the different conditions associated with each host. Just like any other organism, the worm possesses mechanisms that help them respond to environmental insults. It has been hypothesized that a special class of proteins known as Universal Stress Proteins (USPs) are up-regulated during sudden environmental changes, thus assisting the worm to tolerate the unfavourable conditions associated with its developmental cycle. The position of praziquantel as the drug of choice against all schistosome infections has been deemed vulnerable due to mounting concerns over drug pressure and so the need for alternative treatment is now a matter of urgency. Therefore, this review seeks to explore the associations and possible roles of USPs in schistosomiasis as well as the functioning of these proteins in the schistosomulae stage in order to develop new therapeutic interventions against this disease.

Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best

BACKGROUND

Despite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control.

METHODOLOGY

We evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted.

PRINCIPAL FINDINGS

Widespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century.

CONCLUSIONS/SIGNIFICANCE

Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.

Policy Support and Resources Mobilization for the National Schistosomiasis Control Programme in The People's Republic of China

Schistosomiasis remains a public health problem in many developing countries around the world. After the founding of The People's Republic of China, from 1949 till date, all levels of government, from central to local, have been attaching great importance to schistosomiasis control in The People's Republic of China. With considerable policy support and resources mobilization, the national schistosomiasis control programmes have been implemented during the past 65years. Here, we summarize the successful experience of schistosomiasis control during the process. Recommendations for the future management of the Chinese national schistosomiasis elimination programme are put forward after considering the remaining challenges, shortcomings and lessons learnt from 65years of schistosomiasis control drives in The People's Republic of China. They will help to sustain past achievements, foster the attainment of the ultimate goal of schistosomiasis elimination for the country and provide reference for schistosomiasis control programme in other countries.

Epidemiological Features and Effectiveness of Schistosomiasis Control Programme in Mountainous and Hilly Region of The People's Republic of China

Schistosomiasis is a parasitic disease that affects over 200million people worldwide in at least 76 countries, ranking second only after malaria in terms of its socio-economic and public health importance in tropical and subtropical areas of the world. Chinese surveillance data since the mid-1950s have shown that endemic areas are divided into three types based on geographical, ecological and epidemiological factors, such as marshland and lake region, plain region with waterway networks and hilly and mountainous region. As confirmed by numerous epidemiological investigations, schistosomiasis endemic areas of the mountainous type are distributed in 178 counties in 11 provinces of The People's Republic of China. Over the past several decades great success in transmission control has been achieved by implementation of control strategies that were suitable for the mountainous and hilly endemic region.

Health Education as an Important Component in the National Schistosomiasis Control Programme in The People's Republic of China

Schistosomiasis control programme in The People's Republic of China had promoted the mass mobilization of health education in various forms, such as films, drama, traditional opera, poems, slogans, posters, exhibits. This paper is trying to review the impacts of those forms on different endemic settings and targeted populations. In the future, health education and health promotion will still be the effective strategy and one of the interventions in the national control programme for schistosomiasis and other infectious diseases, even in the pre- or posttransmission stages. With the social and economic development and improvement of people's living standard, it is necessary to establish a sustainable mechanism, in combination of health education with health guarantee of improving the quality of life, improving the production and living conditions, changing the unhealthy production methods and lifestyle of the residents in the endemic areas, in order to reach the goal of schistosomiasis elimination in The People's Republic of China.

[Establishment of surveillance and forecast platform of schistosomiasis in key water regions in Hubei Province]

OBJECTIVE

To establish an expression platform of surveillance and forecast for schistosomiasis in key water regions of Hubei Province.

METHODS

The platform of surveillance and forecast for schistosomiasis was established based on Google Earth, GIS Office software, network albums and network video stations. The results of the field surveillance and laboratory testing, and figures and videos were inputted into the established platform, and an information management file was set up to express the information of forecasting.

RESULTS

The operation and expression platform based on Google Earth in key water regions of Hubei Province was successfully established. It was able to provide the forecasting data timely, to achieve off-site and real-time query and sharing.

CONCLUSIONS

The platform based on Google Earth has preferable prospective on field application in Hubei Province.

[Progress of researches on diagnostic methods of current Schistosoma infection]

Now schistosomiasis is still a serious zoonosis which affects human health and hinders the economy development in endemic areas. Accurate diagnosis of the infection of Schistosoma is very significant in reducing hazards to human health and controlling the epidemic of schistosomiasis. This review summarizes recent advances in the laboratory diagnostic methods for current schistosome infection (including pathogenic, immunologic and molecular biologic methods) so as to provide the reference for prevention and control of schistosomiasis in the field.

[Countermeasures and experiences of schistosomiasis control work under new situation of Shengzhou City]

OBJECTIVE

To summarize the experience of Oncomelania hupensis snail control work and explore more effective snail control strategy under the new situation.

METHODS

The data of former snail control work and strategies were collected and analyzed in Shengzhou City from 1995 to 2015.

RESULTS

The snail area was effectively compressed in recent years, and it was decreased by 46.61% and 26.50% in 2014 and 2015 respectively compared with that in the last year.

CONCLUSIONS

To consolidate the snail control achievements, the government should pay more attention to the schistosomiasis control work and establish a targeted effective long-term strategy.

[Impact of self-efficacy on behaviors of contacting infested water among middle school students in Hubei Province]

OBJECTIVE

To explore the impact of self-efficacy on the behavior of contacting schistosome cercarial infested water among middle school students.

METHODS

In the transmission control area and endemic control area of the schistosomiasis endemic regions in Hubei Province, a total of 3 204 middle school students were selected through the stratified cluster random sampling method and investigated by questionnaires.

RESULTS

The incidence rates of contacting infested water with Oncomelania hupensis snails during the past 3 and 12 months among the middle school students were 11.4% (364/3 204) and 14.8% (474/3 204) respectively, while those of contacting indefinite infested water during the past 3 and 12 months were 23.8% (762/3 204) and 28.0% (898/3 204) respectively. The awareness rate of schistosomiasis prevention and control knowledge was 82.1% (2 631/3 204). There were "knowledge-practice separation"in the prevention and control of schistosomiasis among the middle school students. The correlation analysis and Logistic regression analysis showed that the self-efficacy of schistosomiasis protective behavior of middle school students was a protective factor for contacting with infested water, with the adjusted odds ratio values of 0.882, 0.886, 0.914 and 0.927.

CONCLUSIONS

Self-efficacy of schistosomiasis protective behavior is a protective factor for contacting with infested water among middle school students, and improving their self-efficacy may be an effective strategy to settle the problem of"knowledge-practice separation".

Studies of the Transmission Dynamics, Mathematical Model Development and the Control of Schistosome Parasites by Mass Drug Administration in Human Communities

Schistosomiasis is global in extent within developing countries, but more than 90% of the at-risk population lives in sub-Saharan Africa. In total, 261 million people are estimated to require preventive treatment. However, with increasing drug availability through donation, the World Health Organization has set a goal of increasing coverage to 75% of at-risk children in endemic countries and elimination in some regions. In this chapter, we discuss key biological and epidemiological processes involved in the schistosome transmission cycle and review the history of modelling schistosomiasis and the impact of mass drug administration, including both deterministic and stochastic approaches. In particular, we look at the potential impact of the WHO 2020 schistosomiasis treatment goals.

Schistosomiasis: Traverers in Africa

Schistosomiasis is a parasitic infection acquired through freshwater exposure in the tropics. It is an infection that can have devastating implications to military personnel if it is not recognized and treated, especially later in life. While there is an abundance of information available about schistosomiasis in endemic populations, the information on nonendemic populations, such as deployers, is insufficient. Definitive studies for this population are lacking, but there are actions that can and should be taken to prevent infection and to treat patients. This literary review presents a case study, reviews basic science, and explores the information available about schistosomiasis in nonendemic populations. Specifically, the authors provide recommendations for the prevention, diagnosis, and postexposure management in military personnel.

[Effect of comprehensive schistosomiasis control in Changzhou City from 2004 to 2014]

OBJECTIVE

To evaluate the effect of comprehensive schistosomiasis control in Changzhou City in recent 10 years, so as to provide the evidences for formulating the future prevention and control strategy.

METHODS

The work reports and the data of the schistosomiasis comprehensive control projects in Changzhou City from 2004 to 2014 were collected, the infection status of residents and livestock as well the Oncomelania hupensis snail situation were analyzed, and the implementation effect of the comprehensive control projects was evaluated.

RESULTS

From 2004 to 2014, totally 215 368 person-times were examined, and the positive rate of the blood examinations of the population was 0.24% (478/198 356), and there were no positive cases detected out by using the miracidium hatching method. Totally 11 935 domestic animals were detected and no positives were found. From 2004 to 2014, the total area with snails was 92.27 hm², and marshland, inland and mountain environments accounted for 34.75%, 34.82% and 30.43%, respectively. The newly discovered area with snails was 34.40 hm², and marshland, inland and mountain environments accounted for 2.62%, 71.22% and 26.16%, respectively. Totally 8 511 snails were dissected and no schistosome infected snails were found. From 2004 to 2014, a total of 242 600 harmless toilets were built, 2 704 700 domestic animals were reared in pens, 5.82 km-long rivers were dredged, 2 250.11 hm² of protective forests were constructed, a total area of 625.79 hm² were controlled with molluscicides, and an area of 149.58 hm² were environmentally transformed. Totally 5.4 million people received health education. The awareness rate of knowledge on schistosomiasis control of residents was 96.00% in 2014.

CONCLUSIONS

There exists the risks of snails import and diffusion and schistosomiasis resurrection in Changzhou City, but under the condition of continuous implementation of comprehensive control measures, the endemic situation of schistosomiasis is stable and the control achievement is consolidated in this city.

[Endemic status of schistosomiasis in People's Republic of China in 2014]

This report presented the endemic status of schistosomiasis in the People's Republic of China at national level in 2014, and analyzed the data captured from the national schistosomiasis prevention and control system and 81 national schistosomiasis surveillance sites. Among the 12 provinces (municipality and autonomous region) endemic for schistosomiasis japonica in China, 5 provinces (municipality and autonomous region) of Shanghai, Zhejiang, Fujian, Guangdong and Guangxi had achieved transmission interruption, 4 provinces of Sichuan, Yunnan, Jiangsu and Hubei had achieved transmission control, and Anhui, Jiangxi and Hunan provinces were still at infection control until 2014. There were 453 counties (city, district) endemic for schistosomiasis, with 251 million residents, and 30,048 villages endemic for schistosomiasis, with 68 million 507 thousand and 3 hundred residents. Among the 453 endemic counties (city, district), 69.09% (313/453) and 29.80% (135/ 453) endemic counties (city, district) reached the transmission interruption and transmission control respectively while the number of counties (city, district) at the stage of infection control reduced from 34 in 2013 to 5 in 2014 (accounted for 1.10% of the total number of endemic counties, 5/53). Till 2014, 115,614 people were estimated to have schistosomiasis and only 2 acute schistosomiasis cases were reported. In addition, there were 30,880 advanced schistosomiasis cases documented in 2014. In 2014, a total of 9,461,348 individuals received schistosomiasis examinations and 8,270 persons were found stool positives with the reduction rate of 50.96% as compared to that (16,865 cases) in 2013. The Oncomelania hupensis snail survey was performed in 20 123 endemic villages in 2014, and the snails were detected in 5,653 villages, which accounted for 28.09% of total villages, with 13 newly detected villages with snails. The snail survey covered an area of 576,506.37 hm² and snails were found in an area of 364 324.42 hm², including an area of 531.13 hm² detected snails for the first time. No schistosome infected snails were found in 2014. A total of 919,579 head of cattle were raised in the schistosomiasis endemic areas of China. In 2014, 494,620 head of cattle received examinations and only 666 were determined as stool positives. Based on the data from the 81 national schistosomiasis surveillance sites of China, the mean Schistosomajaponicum infection rate was 0.11% and 0.05% in humans and cattle respectively, and no infected snails were detected in 2014. There were 280,855 schistosomiasis cases receiving treatments, with 2,565,555 cases undergoing expanded chemotherapy; there were 798 head of cattle with schistosomiasis receiving treatments, with 408,690 head of cattle undergoing expanded chemotherapy; there was a total 138,923.90 hm² area with snail control by using molluscicides , with actual mollusciciding of 74,538.17 hm²; and there was an environmental modification of 5,331.42 hm². These data demonstrate a decline in the endemic city of schistosomiasis in China in 2014. However, the risk of schistosomiasis transmission remains high in some regions. Further control and effective surveillance should be strengthened to consolidate the achievements and reduce the endemic situation of schistosomiasis in China.

[Effect of schistosomiasis control strategy based on infection source control of Poyang Lake region in Yongxiu County promotion zone]

OBJECTIVE

To evaluate the effect of schistosomiasis control strategy with emphasis on infection source control in the Yongxiu County promotion zone of Poyang Lake region.

METHODS

The Wucheng Township of Yongxiu County was selected as the observation site, and the effect of the comprehensive control strategy was evaluated by using the method of field surveys combined with retrospective investigations.

RESULTS

In 2010, there were 17 persons whose stool tests for schistosome infection were positive, and the number of calculated schistosomiasis patients was 2,331. The infection rate of cattle was 4.5%, and the area with infected Oncomelania hupensis snails was 10.00 hm². In 2011, the comprehensive control strategy was carried out, and in 2012, there were no cattle in the promotion zone. In 2013 and 2014, there were no schistosomiasis patients with positive stool tests. In 2014, no schistosome infected snails were found.

CONCLUSION

The control strategy with emphasis on infection source control effectively controls the transmission of schistosomiasis in Yongxiu County promotion zone.

[Analysis of epidemic situation and control strategy of schistosomiasis in Jiu- jiang City from 2008 to 2014]

OBJECTIVE

To understand the epidemic situation of schistosomiasis in Jiujiang City, so as to provide the evidence for formulating further control strategy.

METHODS

The data of schistosomiasis control were collected in Jiujiang City from 2008 to 2014. and the indicators including the annual schistosome infections of human and cattle, acute schistosome infection, outbreak of schistosomiasis endemic, schistosome infected Oncomelania hupensis snails were analyzed statistically.

RESULTS

Compared with 2008, in 2014, the infection rates of schistosomiasis declined by 98.40% and 92.54% in human and cattle respectively. The area of schistosome infected snails decreased from 103.24 hm² to zero. The occurrence rate of frames with snails and density of living snails declined from 14.86% and 0.334 5/0.1 m² to 6.89% and 0.126 5/0.1 m², respectively. The acute schistosomiasis infection cases occurred except 2011 and 2014.

CONCLUSION

The control strategy emphasizing on infection sources control is effective in Jiujiang City, but the risk of schistosomiasis still exists, and the risk control and schistosomiasis control strategy should be strengthened.

[Impact of implementation of Three Gorges Project on schistosomiasis endemic situation and control in Nanjing City]

OBJECTIVE

To understand the changes of hydrological regime in the Yangtze River and schistosomiasis endemic situation in Nanjing City after the implementation of Three Gorges Project.

METHODS

The data of hydrological regime of the Yangtze River, schistosomiasis epidemic situation, and Oncomelania hupensis snail status were collected and analyzed in Nanjing City from 2002 to 2012.

RESULTS

After the implementation of the Three Gorges Project in 2003, the water level of the Yangtze River slightly rose from January to April, the average water levels in May and August both reduced compared with those in 2002, and the time of water withdrawal was moved up. The water level of the Yangtze River slightly reduced from November to December. The endemic situation of schistosomiasis showed a decline tendency in the areas along the Yangtze River in Nanjing City. In 2012, the rates of human and bovine infected with Schistosoma japonicum both reduced by 100% as compared with those in 2002, and the snail area, infected snail area and snail density were reduced by 48.45%, 100% and 95.76% respectively as compared with those in 2002.

CONCLUSION

After the implementation of the Three Gorges Project, the schistosomiasis endemic situation shows a decline tendency in the areas along the Yangtze River in Nanjing City, but the long-term monitoring still need to be carried out.

[Schistosomiasis monitoring and its cost in population in Danyang City, 2010-2014]

OBJECTIVE

To explore the monitoring method of the infection source of schistosomiasis in the population of the schistosomiasis transmission-interrupted area with Oncomelania hupensis snails.

METHODS

The changes of schistosomiasis among the population were investigated by using the active and passive monitoring methods in Danyang City from 2010 to 2014, and the cost-effectiveness of the two monitoring methods was evaluated.

RESULTS

Totally 49,277 persons were detected for schistosomiasis by dipstick dye immunoassay (DDIA) from 2010 to 2014 and 608 cases were positive, and the positive rate was 1.23%. There were no positive persons by etiology detections. The positive rates of active and passive monitoring methods were 1.61% and 1.13%, respectively and there was a significant difference between them (χ² = 15.982, P < 0.05). The average cost per positive case of the active monitoring was higher than that of the passive monitoring without considering the costs of the mobilization and labor.

CONCLUSION

In the schistosomiasis transmission-interrupted area with snails, the active and passive monitoring methods need to be combined in the future.

[Surveillance of schistosomiasis in national surveillance sites of Zhenjiang City, 2005-2010]

OBJECTIVE

To master the changes of schistosomiasis epidemic situation in national surveillance sites of Zhenjiang City, Jiangsu Province.

METHODS

According to the scheme of the national schistosomiasis surveillance, the Shicheng Village of Yangzhong County and Sanzhou Village of Dantu District were selected as the national schistosomiasis surveillance sites, and from 2005 to 2010, the schistosomiasis morbidity and Oncomelania hupensis status were surveyed and the results were analyzed statistically.

RESULTS

In 2010, in the Shicheng Village, the reduction rates of mean living snail density, infected snail density, area with infected snails, and positive blood tests in residents were 98.4%, 0, 0, 71.8% respectively, and in the Sanzhou Village, the reduction rates were 70.4%, 100%, 100% and 81.5%, respectively compared with those in 2005. No acute infections were found in the 2 villages during the period of 6 consecutive years.

CONCLUSION

In the national surveillance sites of Zhenjiang City, the schistosomiasis morbidity has been effectively controlled. However, the areas with snails change little. Therefore, the comprehensive management of snail environment in the marshland should be strengthened in the future.

[Current prevalence situation and control strategy of schistosomiasis in Yunnan Province]

OBJECTIVE

To evaluate the current prevalence situation of schistosomiasis in Yunnan Province, so as to provide the evidence for making further control strategy.

METHODS

The data of schistosomiasis were collected and analyzed statistically in Yunnan Province in 2014.

RESULTS

There were 7 transmission controlled counties and 11 interrupted counties in Yunnan Province in 2014, and Oncomelania hupensis snails were not found in 5 of the 11 interrupted counties for at least 5 years. In the transmission controlled areas, the schistosomiasis endemic villages, population, farm cattle, and snail areas accounted for 80.94%, 83.72%, 79.32% and 82.00% of whole schistosomiasis endemic areas in Yunnan Province, respectively. The infection source was not completely eliminated.

CONCLUSION

In the transmission controlled areas, the elimination of infection source should still be strengthened; in the transmission interrupted areas, the import infection sources should be prevented.

[Dynamics of CD4⁺ T cell subsets and their roles in schistosome infections: a review]

Schistosomiasis is a chronic helminthic disease that affects about two hundred millions of people in the world. The pathogenesis of schistosome infection is primarily due to hepatic and intestinal granuloma formation around deposited eggs and subsequent fibrosis. It is known that CD4⁺ T cell subsets play critical roles in the host immunity and immunopathogenesis to schistosome infections, in which T helper 1 (Th1) and Th2 cells are major effector T cell subsets, whereas T regulatory (Treg) cells exert immunosuppressive roles in general. The recently discovered Th17 cells are also actively involved in the immune responses to the infection. During the infection, these T cell subsets cross-talk and exhibit different kinetics and roles in the control and regulation of infection progress and fibrosis. This review summarizes current findings of Th1, Th2, Th17 and Treg cells and their effector cytokines in schistosome infection.

[Effect of integrated measures on schistosomiasis transmission--interruption in hilly areas]

OBJECTIVE

To evaluate the effect of control integrative measures which persist in snail eradication and chemotherapy on schistosomiasis transmission-interruption in hilly areas.

METHODS

The data of integrated control and endemic situation of schistosomiasis from 2004 to 2014 were collected, and the control effect of integrated measures was evaluated.

RESULTS

From 2004 to 2014, both the Oncomelania hupensis snail area and density of living snails of Jurong City were reduced from 43.13 hm2 and 1.48 snails/0.1 m2 to 0; the residents' seropositive rate declined continuously; the residents' and students' awareness rates on schistosomiasis control were increased from 88.43% and 82.04% to 92.56% and 95.74% respectively; the snail area was significantly negatively correlated with the coverage rate of snail control (r = -0.864, P < 0.05).

CONCLUSIONS

In the hilly areas, the schistosomiasis control integrated measures which persist in snail eradication and chemotherapy could control the endemic situation rapidly and steadily, accelerating to achieve the goal of schistosomiasis transmission-interruption.

[Risk assessment of schistosomiasis transmission on rescue workers involved in "Oriental Star shipwreck event"]

OBJECTIVE

To assess the impact of the "Oriental Star shipwreck event" on the risk of schistosomiasis transmission in Jianli County, Hubei Province, so as to provide the evidence for formulating appropriate measures of schistosomiasis prevention and control.

METHODS

Based on the field observation and investigation, the data of the on-the-spot rescue and the historical endemic situation of schistosomiasis in Jianli County were collected and analyzed. Meanwhile, the focus group discussion and risk matrix were conducted to assess the risk of schistosome infection of the rescuers.

RESULTS

Over 10 000 rescuers participated in the search operation, including the armed police forces, local people, reservists and so on. The armed police forces were the major components, which accounted for 39%. Jianli country was schistosomiasis endemic area with a high infection level in history, but the endemic situation had been mitigated significantly after years of positive prevention and treatment; the schistosome infection rate of population was 0.44% in 2014 and the Oncomelania hupensis snail area was only 6.6 hm2 around the rescue areas in the upstream and downstream. In addition, the snail density was not high, and no infected snails had been found for 11 years. The risk of schistosome infection was in the medium level.

CONCLUSIONS

Though there exists the schistosome infection risk in the water area where the accident happened, the probability of occurrence is not high. In order to prevent the outbreak and endemic of schistosomiasis, the protection measures and health education to the rescuers as well as snail control and monitoring, and early-warning should be strengthened.

[Analysis of schistosomiasis situation at a surveillance site in Kailhua County, Zhejiang Province from 2008 to 2014]

OBJECTIVE

To master the dynamics of schistosomiasis situation in Kaihua County, so as to provide the evidence for formulating the prevention and control scheme.

METHODS

According to the "Schistosomiasis Monitoring Work Program in Zhejiang Province", the Oncomelania hupensis snail status, schistosome infections of residents and livestock, and the influencing factors were investigated.

RESULTS

Totally 62 snail sites were discovered, the area with snails was 2.30 hm2, the snail density was 0.023 snail/0.1 m2, and the snail status declined with time. No schistosome infected snails, local residents, mobile people or livestock were found.

CONCLUSION

The endemic situation of schistosomiasis is stable in Kaihua County, but the surveillance of snail situation and mobile population is still needed.

[Endemic situation of schistosomiasis in Tongling County of Anhui Province from 2009 to 2014]

OBJECTIVE

To understand the endemic situation of schistosomiasis in Tongling County of Anhui Province, so as to provide the evidence for summarizing the "Twelfth Five-Year Plan" and formulating the "Thirteenth Five-Year Plan".

METHODS

The data of schistosomiasis control reports and other information about Oncomelania hupensis status and schistosomiasis situation of population and livestock were collected and analyzed statistically in Tongling County from 2009 to 2014.

RESULTS

From 2009 to 2014, the schistosome infection rate and blood positive rate of the population decreased significantly, and only one case of acute schistosome infection was found in 2009. The schistosome infection rate of livestock decreased significantly, and the decreasing rate was 91.10% from 2009 to 2010. From 2009 to 2014, the snail area and average density of living snails presented decreasing trends but the densities of living snails increased in 2011 and 2012. After 2011, no schistosome infected snails were found.

CONCLUSIONS

The schistosome infection rate of population has been controlled at a low level in Tongling County, but the snail area is still large in the marshland and lake regions, and the density of living snails is relatively high in the inland. Therefore, the schistosomiasis control work, especially snail control, still should be strengthened.