Transmission-Blocking Vaccines against Schistosomiasis Japonica.

Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can generate 1000-2200 eggs per day, which is about 3- to 15-fold greater than the egg output of other schistosome species. Bovines (water buffalo and cattle) are the predominant definitive hosts and are estimated to generate up to 90% of parasite eggs released into the environment in rural endemic areas where these hosts and humans are present. Here, we highlight the necessity of developing veterinary transmission-blocking vaccines for bovines to better control the disease and review potential vaccine candidates. We also point out that the approach to producing efficacious transmission-blocking animal-based vaccines before moving on to human vaccines is crucial. This will result in effective and feasible public health outcomes in agreement with the One Health concept to achieve optimum health for people, animals, and the environment. Indeed, incorporating a veterinary-based transmission vaccine, coupled with interventions such as human mass drug administration, improved sanitation and hygiene, health education, and snail control, would be invaluable to eliminating zoonotic schistosomiasis.

The prevailing infection of Schistosoma japonicum and other zoonotic parasites in bubaline reservoir hosts in the ricefield of lake ecosystem: the case of Lake Mainit, Philippines.

Bovines are important reservoir hosts of schistosomiasis, placing humans and animals in rice fields areas at risk of infection. This study reported the prevailing infection of zoonotic parasites from bovine feces in the rice fields adjacent to Lake Mainit, Philippines. Formalin Ethyl Acetate Sedimentation was performed on 124 bovine fecal samples from rice fields and documented eggs and cysts from seven parasites: Schistosoma japonicum, Fasciola gigantica, Ascaris sp., Strongyloides sp., Balantidium coli, coccidian oocyst and a hookworm species. Among these parasites, F. gigantica harboured the highest infection with a 100% prevalence rate, followed by hookworms (51.61%), B. coli (30.64%) and S. japonicum (12.09%), respectively. The intensity of infection of S. japonicum eggs per gram (MPEG = 4.19) among bovines is categorized as 'light.' Bovine contamination index (BCI) calculations revealed that, on average, infected bovines in rice fields excrete 104 750 S. japonicum eggs daily. However, across all ricefield stations, bovines were heavily infected with fascioliasis with BCI at 162 700 F. gigantica eggs per day. The study reports that apart from the persistent cases of schistosomiasis in the area, bovines in these rice fields are also heavily infected with fascioliasis. The study confirms the critical role of bovines as a reservoir host for continued infection of schistosomiasis, fascioliasis and other diseases in the rice fields of Lake Mainit. Immediate intervention to manage the spread of these diseases in bovines is recommended.

Schistosomiasis in the People's Republic of China - down but not out.

Schistosomiasis has been subjected to extensive control efforts in the People's Republic of China (China) which aims to eliminate the disease by 2030. We describe baseline results of a longitudinal cohort study undertaken in the Dongting and Poyang lakes areas of central China designed to determine the prevalence of Schistosoma japonicum in humans, animals (goats and bovines) and Oncomelania snails utilizing molecular diagnostics procedures. Data from the Chinese National Schistosomiasis Control Programme (CNSCP) were compared with the molecular results obtained.Sixteen villages from Hunan and Jiangxi provinces were surveyed; animals were only found in Hunan. The prevalence of schistosomiasis in humans was 1.8% in Jiangxi and 8.0% in Hunan determined by real-time polymerase chain reaction (PCR), while 18.3% of animals were positive by digital droplet PCR. The CNSCP data indicated that all villages harboured S. japonicum-infected individuals, detected serologically by indirect haemagglutination assay (IHA), but very few, if any, of these were subsequently positive by Kato-Katz (KK).Based on the outcome of the IHA and KK results, the CNSCP incorporates targeted human praziquantel chemotherapy but this approach can miss some infections as evidenced by the results reported here. Sensitive molecular diagnostics can play a key role in the elimination of schistosomiasis in China and inform control measures allowing for a more systematic approach to treatment.

Molecular characterization, expression profile, and preliminary evaluation of diagnostic potential of CD63 in Schistosoma japonicum.

Schistosomes are the causative agents of human schistosomiasis, which is endemic in tropical and subtropical zones. CD63 is a member of the tetraspanin protein family widely expressed among eukaryotes. Previously, we identified a CD63 homolog from extracellular vesicles isolated from Schistosoma japonicum. In this study, we characterized this CD63 homolog using a molecular approach and evaluated the potential of its recombinant protein for the diagnosis of schistosomiasis. A sequence alignment indicated that S. japonicum CD63 (SjCD63) has sequence identities of 76 and 28% with S. mansoni and human CD63, respectively. A phylogenetic analysis displayed that S. japonicum CD63 is related to S. mansoni and Opisthorchis viverrini CD63. The cDNA of SjCD63 was 740 bp long with an expected protein size of 23.58 kDa. A RT-qPCR analysis revealed significantly higher expression of SjCD63 mRNA in adult worms on days 21, 28, and 35 than in 7-day schistosomula, cercariae, and eggs. In addition, recombinant SjCD63 protein detected by ELISA revealed significantly higher optical density values compared to that of the negative control in both S. japonicum-infected mouse and rabbit sera, providing preliminary evidence for its diagnostic potential. Overall, these results provide insight into the molecular properties of SjCD63, its expression profiles, and its preliminary diagnostic potential.

Schistosoma japonicum in Samar, the Philippines: infection in dogs and rats as a possible risk factor for human infection.

The role that animals play in the transmission of Schistosoma japonicum to humans in the Philippines remains uncertain and prior studies have not included several species, adjustment for misclassification error and clustering, or used a cohort design. A cohort study of 2468 people providing stool samples at 12 months following praziquantel treatment in 50 villages of Western Samar, the Philippines, was conducted. Stool samples from dogs, cats, rats, and water buffaloes were collected at baseline (2003-2004) and follow-up (2005). Latent-class hierarchical Bayesian log-binomial models adjusting for misclassification errors in diagnostic tests were used. The village-level baseline and follow-up prevalences of cat, dog, and rat S. japonicum infection were associated with the 12-month cumulative incidence of human S. japonicum infection, with similar magnitude and precision of effect, but correlation between infection levels made it difficult to divide their respective effects. The cumulative incidence ratios associated with a 1% increase in the prevalence of infection in dogs at baseline and in rats at follow-up were 1·04 [95% Bayesian credible interval (BCI) 1·02-1·07] and 1·02 (95% BCI 1·01-1·04), respectively, when both species were entered in the model. Dogs appear to play a role in human schistosomiasis infection while rats could be used as schistosomiasis sentinels.

Development and optimization of cocktail-ELISA for a unified surveillance of zoonotic schistosomiasis in multiple host species.

The zoonotic characteristic of the human parasite Schistosoma japonicum infecting a significant number of wild and domestic animals highlights the need to develop a unified surveillance in multiple host species for a strengthened schistosomiasis control. It has been shown in several studies that water buffaloes and dogs are considered important reservoirs in the transmission of the schistosome parasite to humans. Recombinant antigens like thioredoxin peroxidase-1 (SjTPx-1) and tandem repeat proteins (Sj1TR, Sj7TR) have been shown to be good diagnostic antigens individually in humans, water buffaloes, and dogs in previous studies. Mixing these antigens together in a cocktail-ELISA might not only improve their diagnostic potentials but rather produce a multi-host species detection means for zoonotic schistosomiasis. In this study, we aimed to develop and optimize cocktail-ELISA by testing different combinations of these recombinant antigens in humans, water buffaloes, and dogs. As compared with the diagnostic potential calculated for each of the three recombinant antigens used, their combination has presented improved specificities, positive predictive values, and kappa values. Using samples collected from various endemic areas in the Philippines, results showed that the combination of SjTPx-1/Sj7TR/Sj1TR has the highest sensitivity in humans (84.1 %), water buffaloes, and dogs (80 %) and specificity (100 %) in all host species. This study therefore suggests the use of cocktail-ELISA in improving the zoonotic surveillance in schistosomiasis endemic areas.

[Intelligent identification of livestock, a source of Schistosoma japonicum infection, based on deep learning of unmanned aerial vehicle images].

OBJECTIVE: To develop an intelligent recognition model based on deep learning algorithms of unmanned aerial vehicle (UAV) images, and to preliminarily explore the value of this model for remote identification, monitoring and management of cattle, a source of Schistosoma japonicum infection. METHODS: Oncomelania hupensis snail-infested marshlands around the Poyang Lake area were selected as the study area. Image datasets of the study area were captured by aerial photography with UAV and subjected to augmentation. Cattle in the sample database were annotated with the annotation software VGG Image Annotator to create the morphological recognition labels for cattle. A model was created for intelligent recognition of livestock based on deep learning-based Mask R-convolutional neural network (CNN) algorithms. The performance of the model for cattle recognition was evaluated with accuracy, precision, recall, F1 score and mean precision. RESULTS: A total of 200 original UAV images were obtained, and 410 images were yielded following data augmentation. A total of 2 860 training samples of cattle recognition were labeled. The created deep learning-based Mask R-CNN model converged following 200 iterations, with an accuracy of 88.01%, precision of 92.33%, recall of 94.06%, F1 score of 93.19%, and mean precision of 92.27%, and the model was effective to detect and segment the morphological features of cattle. CONCLUSIONS: The deep learning-based Mask R-CNN model is highly accurate for recognition of cattle based on UAV images, which is feasible for remote intelligent recognition, monitoring, and management of the source of S. japonicum infection.

Recognizing and monitoring infectious sources of schistosomiasis by developing deep learning models with high-resolution remote sensing images.

BACKGROUND: China is progressing towards the goal of schistosomiasis elimination, but there are still some problems, such as difficult management of infection source and snail control. This study aimed to develop deep learning models with high-resolution remote sensing images for recognizing and monitoring livestock bovine, which is an intermediate source of Schistosoma japonicum infection, and to evaluate the effectiveness of the models for real-world application. METHODS: The dataset of livestock bovine's spatial distribution was collected from the Chinese National Platform for Common Geospatial Information Services. The high-resolution remote sensing images were further divided into training data, test data, and validation data for model development. Two recognition models based on deep learning methods (ENVINet5 and Mask R-CNN) were developed with reference to the training datasets. The performance of the developed models was evaluated by the performance metrics of precision, recall, and F1-score. RESULTS: A total of 50 typical image areas were selected, 1125 bovine objectives were labeled by the ENVINet5 model and 1277 bovine objectives were labeled by the Mask R-CNN model. For the ENVINet5 model, a total of 1598 records of bovine distribution were recognized. The model precision and recall were 81.9% and 80.2%, respectively. The F1 score was 0.81. For the Mask R-CNN mode, 1679 records of bovine objectives were identified. The model precision and recall were 87.3% and 85.2%, respectively. The F1 score was 0.87. When applying the developed models to real-world schistosomiasis-endemic regions, there were 63 bovine objectives in the original image, 53 records were extracted using the ENVINet5 model, and 57 records were extracted using the Mask R-CNN model. The successful recognition ratios were 84.1% and 90.5% for the respectively developed models. CONCLUSION: The ENVINet5 model is very feasible when the bovine distribution is low in structure with few samples. The Mask R-CNN model has a good framework design and runs highly efficiently. The livestock recognition models developed using deep learning methods with high-resolution remote sensing images accurately recognize the spatial distribution of livestock, which could enable precise control of schistosomiasis.

First bovine vaccine to prevent human schistosomiasis - a cluster randomised Phase 3 clinical trial.

OBJECTIVE: Schistosomiasis is a neglected tropical parasitic disease caused by blood flukes of the genus Schistosoma. Schistosoma japonicum is zoonotic in China, the Philippines, and Indonesia, with bovines acting as major reservoirs of human infection. The primary objective of the trial was to examine the impact of a combination of human mass chemotherapy, snail control through mollusciciding, and SjCTPI bovine vaccination on the rate of human infection. METHODS: A 5-year phase IIIa cluster randomized control trial was conducted among 18 schistosomiasis-endemic villages comprising 18,221 residents in Northern Samar, The Philippines. RESULTS: Overall, bovine vaccination resulted in a statistically significant decrease in human infection (relative risk [RR] = 0.75; 95% confidence interval [CI] = 0.69 to 0.82) across all trial follow-ups. The best outcome of the trial was when bovine vaccination was combined with snail mollusciciding. This combination resulted in a 31% reduction (RR = 0.69; 95% CI = 0.61 to 0.78) in human infection. CONCLUSION: This is the first trial to demonstrate the effectiveness of a bovine vaccine for schistosomiasis in reducing human schistosome infection. The trial is registered with Australian New Zealand Clinical Trials Registry (ACTRN12619001048178).

A strategy to control transmission of Schistosoma japonicum in China.

BACKGROUND: Schistosoma japonicum causes an infection involving humans, livestock, and snails and is a significant cause of morbidity in China. METHODS: We evaluated a comprehensive control strategy in two intervention villages and two control villages along Poyang Lake in the southeastern province of Jiangxi, where annual synchronous chemotherapy is routinely used. New interventions, implemented from 2005 through 2007, included removing cattle from snail-infested grasslands, providing farmers with mechanized farm equipment, improving sanitation by supplying tap water and building lavatories and latrines, providing boats with fecal-matter containers, and implementing an intensive health-education program. During the intervention period, we observed changes in S. japonicum infection in humans, measured the rate of infection in snails, and tested the infectivity of lake water in mice. RESULTS: After three transmission seasons, the rate of infection in humans decreased to less than 1.0% in the intervention villages, from 11.3% to 0.7% in one village and from 4.0% to 0.9% in the other (P<0.001 for both comparisons). The rate of infection in humans in control villages fluctuated but remained at baseline levels. In intervention villages, the percentage of sampling sites with infected snails decreased from 2.2% to 0.1% in one grassland area and from 0.3% to no infection in the other (P<0.001 for both comparisons). The rate of infection in mice after exposure to lake water decreased from 79% to no infection (P<0.001). CONCLUSIONS: A comprehensive control strategy based on interventions to reduce the rate of transmission of S. japonicum infection from cattle and humans to snails was highly effective. These interventions have been adopted as the national strategy to control schistosomiasis in China.

Comparison of worm development and host immune responses in natural hosts of Schistosoma japonicum, yellow cattle and water buffalo.

BACKGROUND: Yellow cattle and water buffalo are two of the most important natural hosts for Schistosoma japonicum in China. Previous observation has revealed that yellow cattle are more suited to the development of S. japonicum than water buffalo. Understanding more about the molecular mechanisms involved in worm development, as well as the pathological and immunological differences between yellow cattle and water buffalo post infection with S japonicum will provide useful information for the vaccine design and its delivery procedure. RESULTS: The worm length (p < 0.01), worm recovery rate (p < 0.01) and the percentage of paired worms (p < 0.01) were significantly greater in yellow cattle than those in water buffalo. There were many white egg granulomas in the livers of yellow cattle, but fewer were observed in water buffalo at 7 weeks post infection. The livers of infected yellow cattle contained significantly increased accumulation of inflammatory cells, and the schistosome eggs were surrounded with large amounts of eosinophil infiltration. In contrast, no hepatocyte swelling or lymphocyte infiltration, and fewer white blood cells, was observed in water buffalo. The percentage of CD4⁺ T cells was higher in yellow cattle, while the percentage of CD8⁺ T cells was higher in water buffalo from pre-infection to 7 w post infection. The CD4/CD8 ratios were decreased in both species after challenge with schistosomes. Comparing with water buffalo, the IFN-γ level was higher and decreased significantly, while the IL-4 level was lower and increased gradually in yellow cattle from pre-infection to 7 w post infection. CONCLUSIONS: In this study, we confirmed that yellow cattle were more suited to the development of S. japonicum than water buffalo, and more serious pathological damage was observed in infected yellow cattle. Immunological analysis suggested that CD4⁺ T cells might be an integral component of the immune response and might associate with worm development in yellow cattle. A shift from Th1 to Th2 type polarized immunity was only shown clearly in schistosome-infected yellow cattle, but no shift in water buffalo. The results provide valuable information for increased understanding of host-schistosome interactions, and for control of schistosomiasis.

What is the role of health education in the integrated strategy to control transmission of Schistosoma japonicum in China?

In 2009, Wang et al.'s field trial published in the New England Journal of Medicine, reported that a comprehensive strategy aiming to reduce the roles of humans and cattle as sources of Schistosoma japonicum infection in snails was implemented and proved effective and promising in dramatically reducing the percentage of infected humans and snails, which had been extended to other endemic provinces in China afterwards. This implies that the integrated schistosomiasis-control strategies of interventions including political will, financial support and residents' participation to control human and bovine sources of S. japonicum infection in snails may direct to successfully interrupt the parasitic transmission and to ultimately eliminate schistosomiasis. Confusingly, however, the role of health education, which is a critical part of the integrated strategy and should play an active role in schistosomiasis control, was not reflected. We wish the authors to provide the readers a better and clearer statement of the role of health education as part of the integrated control strategy and so we write this comment.

[Protective effect of SjC23-Hsp70 DNA vaccine and interleukin-12 on Schistosoma japonicum infection in water buffalos].

OBJECTIVE: To determine the immune-protective effect of Japan Schistosoma (Chinese mainland strain) 23 kD membrane protein-heat shock protein (SjC23-Hsp70) DNA vaccine plus adjuvantinduced interleukin-12 (IL-12) plasmid DNA on Schistosoma japonicum infection in water buffalos. METHODS: Forty-five health water buffalos (8-10 months old) in non-endemic area of schistosomiasis were randomly assigned into group A (SjC23-Hsp70+IL-12, 300 µg), group B (SjC23+IL-12, 300 µg) and group C (pVAX+IL-12, 300 µg), 15 in each group. Each buffalo was immuned by shoulder intramuscular injection for 3 times, at an interval of 28 days. Twenty-eight days after the last immunization, each buffalo was infected with 1000 Japan cercariae of Schistosoma. Fecal examinations were conducted 2 days and 1 day before the perfusion, and on the day of perfusion. The number of hatching miracidia and eggs per gram feces was recorded. Fifty-six days after the infection, the buffalos were sacrificed and perfused via the descending aorta. The recovered adult worms and eggs in the liver tissue were counted. RESULTS: We compared group A and B with group C: the estrogen reduction rate was 45.7% and 26.61%; bug reduction rate was 44.51% and 25.84%; the fecal egg reduction rate was 41.1% and 31.63%; the miracidium reduction rate was 48.11% and 38.07%; and the liver egg reduction rate was 43.39% and 31.95%. The above rates in group A were higher than those in group B (P<0.05). CONCLUSION: SjC23-Hsp70 DNA vaccine combined with IL-12 may have a significant immunoprotective effect on buffalos.

A simple and efficient miracidium hatching technique for preparing a single-genome DNA sample of Schistosoma japonicum.

In this study, a simple and efficient miracidium hatching technique (MHT) protocol for preparing a single-genome DNA of Schistosoma japonicum was proposed. The protocol was designed with 96-well plates to collect a miracidium for single-genome DNA preparation, and the effects of lighting conditions on hatching rates were evaluated. The highest hatching rate was recorded under sunlight (92.4%), followed by fluorescent light (88.0%), and the lowest rate was recorded under the dark condition (4.7%). The results suggested for the first time, to our knowledge, that sunlight was efficient for this simple MHT protocol. Successful amplification of microsatellite marker genes using DNA isolated from a single miracidium also confirmed the quality of the single-genome DNA for subsequent applications.

[Trends in the prevalence of schistosomiasis in Anhui Province from 2004 to 2020 based on Joinpoint regression analysis].

OBJECTIVE: To investigate the changing trends in the prevalence of schistosomiasis in Anhui Province from 2004 to 2020, so as to provide the evidence for formulating the schistosomiasis elimination strategy in the province. METHODS: The epidemiological data of schistosomiasis in Anhui Province from 2004 to 2020 were collected, and the trends in the endemic status of schistosomiasis were analyzed using a Joinpoint regression model. The trends in the prevalence of Schistosoma japonicum infections in humans, bovines and Oncomelania hupensis were measured in Anhui Province from 2004 to 2020 using average annual percent change (AAPC), and the correlations among the changing trends in the prevalence of S. japonicum infections in humans, bovines and O. hupensis snail status were evaluated using Pearson correlation analysis. RESULTS: The prevalence of S.japonicum human infections continued to decline in Anhui Province from 2004 to 2020, with an annual mean decline of 14.8% [AAPC = -14.8%, 95% confidential interval (CI): (-18.9%, -10.5%), P < 0.01]. The prevalence of S. japonicum infections continued to decline in bovines in Anhui Province from 2004 to 2015 [AAPC = -31.3%, 95%CI: (-35.1%, -27.2%), P < 0.01], and was 0 for 5 successive years from 2016 to 2020. During the period from 2004 to 2020, there was an annual mean decline of 0.7% in areas of snail habitats [AAPC = -0.7%, 95%CI: (-1.2%, 0.3%), P < 0.05] and an annual mean decline of 9.2% in the density of living snails [AAPC = -9.2%, 95%CI: (-18.3%, 1.0%), P = 0.08] in Anhui Province from 2004 to 2020, and an annual mean decline of 35.6% was found in the density of S. japonicum-infected snails [AAPC = -35.6%, 95%CI: (-49.2%, -18.3%), P < 0.01] from 2004 to 2012, with no infected snails detected in Anhui Province from 2013 to 2020. There were significant correlations in the prevalence of S. japonicum infections between humans and bovines (r = 0.959, P < 0.01), between the prevalence of S. japonicum human infections and the density of S. japonicum-infected snails (r = 0.823, P < 0.01) and between the prevalence of S. japonicum infections in bovines and the density of S. japonicum-infected snails (r = 0.902, P < 0.01). CONCLUSIONS: The prevalence of S. japonicum infections appeared a decline in humans, bovines and O. hupensis in Anhui Province from 2004 to 2020, and significant correlations were found among the changing trends in the prevalence of S. japonicum human infections, the prevalence of S. japonicum bovine infections and the density of S. japonicum-infected O. hupensis snails. Because of a minor decline in the area of snail habitats and widespread distribution of O. hupensis, however, there is still a risk of schistosomiasis transmission, and precision control for schistosomiasis remains to be reinforced in Anhui Province.

[Investigation on prevalence of Schistosoma japonicum infections in wild mice in Shitai County, Anhui Province, 2018].

OBJECTIVE: To investigate the prevalence of Schistosoma japonicum infection in wild mice in Shitai County, Anhui Province, so as to provide insights into precise control of the source of S. japonicum infections. METHODS: Wild mice were captured using the trapping method for three successive nights at snail-infested settings from Jitan Village of Jitan Township, and Shiquan Village and Xibai Village of Dingxiang Township, Shitai County, Anhui Province in June and October, 2018. All trapped wild mice were sacrificed and liver and mesenteric vein specimens were collected for detection of S. japonicum eggs using microscopy, while the fecal samples in mouse intestines were collected for identification of S. japonicum infections using Kato-Katz technique. In addition, the population density of trapped wild mice was estimated and the prevalence of S. japonicum infection was calculated in trapped wild mice. RESULTS: A total of 376 wild mice were trapped from three villages in Shitai County. The population density of trapped wild mice was 9.1% (376/4 124), and the prevalence of S. japonicum infection was 24.2% (91/376) in trapped wild mice. The highest prevalence of S. japonicum infection was detected in Shiquan Village of Dingxiang Township (30.1%), and the lowest prevalence was seen in Xibai Village of Dingxiang Township; however, there was no significant difference in the prevalence of S. japonicum infection in trapped wild mice among three villages (χ2= 4.111, P > 0.05). In addition, there was no significant difference in the prevalence of S. japonicum infection in wild mice captured between on June (26.8%, 34/127) and October (22.9%, 57/249) (χ2 = 0.690, P = 0.406). The trapped wild mice included 6 species, including Rattus norvegicus, Niviventer niviventer, R. losea, Apodemus agrarius, Mus musculus and N. coning, and the two highest prevalence of S. japonicum infection was detected in R. losea (34.9%, 22/63) and R. norvegicus (31.2%, 44/141). CONCLUSIONS: The prevalence of S. japonicum infections is high in wild mice in Shitai County, and there is a natural focus of schistosomiasis transmission in Shitai County.

Predictors of bovine Schistosoma japonicum infection in rural Sichuan, China.

In China, bovines are believed to be the most common animal source of human schistosomiasis infections, though little is known about what factors promote bovine infections. The current body of literature features inconsistent, and sometimes contradictory results, and to date, few studies have looked beyond physical characteristics to identify the broader environmental conditions that predict bovine schistosomiasis. Because schistosomiasis is a sanitation-related, water-borne disease transmitted by many animals, we hypothesised that several environmental factors - such as the lack of improved sanitation systems, or participation in agricultural production that is water-intensive - could promote schistosomiasis infection in bovines. Using data collected as part of a repeat cross-sectional study conducted in rural villages in Sichuan, China from 2007 to 2016, we used a Random Forests, machine learning approach to identify the best physical and environmental predictors of bovine Schistosoma japonicum infection. Candidate predictors included: (i) physical/biological characteristics of bovines, (ii) human sources of environmental schistosomes, (iii) socio-economic indicators, (iv) animal reservoirs, and (v) agricultural practices. The density of bovines in a village and agricultural practices such as the area of rice and dry summer crops planted, and the use of night soil as an agricultural fertilizer, were among the top predictors of bovine S. japonicum infection in all collection years. Additionally, human infection prevalence, pig ownership and bovine age were found to be strong predictors of bovine infection in at least 1 year. Our findings highlight that presumptively treating bovines in villages with high bovine density or human infection prevalence may help to interrupt transmission. Furthermore, village-level predictors were stronger predictors of bovine infection than household-level predictors, suggesting future investigations may need to apply a broad ecological lens to identify potential underlying sources of persistent transmission.

Development of a Recombinase Polymerase Amplification Assay for Schistosomiasis Japonica Diagnosis in the Experimental Mice and Domestic Goats.

Although the prevalence of schistosomiasis japonica has declined gradually in China, more accurate and sensitive diagnostic methods are urgently needed for the prevention and control of this disease. Molecular diagnostic methods are advantageous in terms of sensitivity and specificity, but they are time-consuming and require expensive instruments and skilled personnel, which limits their application in low-resource settings. In this study, an isothermal DNA amplification assay and recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD) were set up. It was used to detect S. japonicum infections in experimental mice and domestic goats by amplifying a specific DNA fragment of S. japonicum. The lower limit of detection for the LFD-RPA assay was evaluated using dilutions of plasmid containing the target sequence. Cross-reactivity was evaluated using genomic DNA from eight other parasites. The effectiveness of the LFD-RPA assay was verified by assessing 36 positive plasma samples and 36 negative plasma samples from mice. The LFD-RPA assay and real-time PCR were also used to assess 48 schistosomiasis japonica-positive plasma samples and 53 negative plasma samples from goats. The LFD-RPA assay could detect 2.6 femtogram (fg) of S. japonicum target DNA (~39 fg genomic DNA of S. japonicum), only 10-fold less sensitive than real-time PCR assay. There was no cross-reactivity with DNA from the other eight parasites, such as Haemonchus contortus and Spirometra. The whole amplification process could be completed within 15 min at 39°C, and the results can be observed easily using the LFD. The sensitivity and specificity of the LFD-RPA assay were 97.22% (35/36, 95% CI, 85.47%-99.93%) and 100% (36/36, 95% CI, 90.26%-100%) in mice, and 93.75% (45/48, 95% CI, 82.80%-98.69%) and 100% (53/53, 95% CI, 93.28%-100%) in goats. By comparison, the sensitivity and specificity of real-time PCR were 100% (36/36, 95% CI, 90.26%-100%) and 100% (36/36, 95% CI, 90.26%-100%) for mice, and 97.92% (47/48, 95% CI, 88.93%-99.95%) and 100% (53/53, 95% CI, 93.28%-100%) for goats. The LFD-RPA assay exhibits high sensitivity and specificity for the diagnosis of schistosomiasis japonica, and it is an alternative method for diagnosis schistosomiasis japonica in low resource setting.

High prevalence of Schistosoma japonicum by perfusion in naturally exposed water buffalo in a region of the Philippines endemic for human schistosomiasis.

In the past decade, ecological surveys emphasized rats and dogs as the most significant animal reservoirs for Schistosoma japonicum (S.j) in the Philippines. However, recent studies demonstrated 51-91% prevalence of schistosomiasis among water buffalo using qPCR in the Sj endemic regions in the Philippines. In order to resolve the inconsistency of reported surveys regarding Sj endemicity among carabao, a domestic water buffalo that is the most important draught animal, we introduced 42 schistosome negative water buffalo to Macanip, Jaro municipality, Leyte, the Philippines, a subsistence rice-farming village that has been the focus of schistosomiasis japonica studies of our group for the past 20 years. We conducted perfusion to the remaining 34 buffalo that survived 10 months of nature exposure and Typhoon Haiyan. Thirty-three water buffalo were found to be positive with at least 1 pair of worms from the mesenteric vein. The infection rate is 97%, with the worm burden of 94 (95% confidence interval, 49-138 worms) worms. To our knowledge, this is the first report about S. japonicum worm burden in naturally infected water buffalo in the Philippines. The fact that with less than one-year of exposure, in this human schistosomiasis endemic area, only 1 out of 34 water buffalo was uninfected is striking. Urgent attention is needed for a cost-effective technique for monitoring Sj infection in animals and humans. Meanwhile, intervention implementation, including water buffalo treatment and vaccination, should be taken into consideration.

[Endemic situation of schistosomiasis in national surveillance sites of Zhejiang Province from 2015 to 2019].

OBJECTIVE: To analyze the endemic situation of schistosomiasis in national surveillance sites of Zhejiang Province, so as to provide the scientific evidence for formulating the new schistosomiasis surveillance program and consolidating schistosomiasis elimination achievements. METHODS: A total of 54 to 55 national surveillance sites and 6 risk monitoring sites were assigned in historical endemic regions of Zhejiang Province from 2015 to 2019, where the Schistosoma japonicum infections in humans, livestock, snails and wild feces were monitored. All data pertaining to the surveillance results were descriptively analyzed. RESULTS: There were 34 530 person-time local residents receiving serological screening for S. japonicum infections in national surveillance sites of Zhejiang Province from 2015 to 2019, and the seroprevalance of S. japonicum infections were 0.29% to 0.68%; however, no egg-positives were detected. During the period from 2015 to 2019, there were 62 086 person-time mobile populations receiving serological screening for S. japonicum infections in national surveillance sites of Zhejiang Province, and the seroprevalance of S. japonicum infections were 0.32% to 0.56%; additionally, there were 27 egg-positives identified, including 3 imported cases with schistosomiasis haematobia and one case with acute schistosomiasis japonica, indicating that the adjusted prevalence of Schistosoma infections were 0.01% to 0.07% among mobile populations. A total of 829 livestock were examined for S. japonicum infections, with no positives detected. There were 10.55 hm2 and 2.89 hm2 snail habitats found in national surveillance sites and risk monitoring sites of Zhejiang Province during the 5-year period, respectively; however, no S. japonicum infections were identified in snails. Moreover, a total of 305 wild feces were tested for S. japonicum infections, and no egg-positives were identified. CONCLUSIONS: The schistosomiasis elimination achievement have been consolidated in Zhejiang Province; however, the risk factors of re-emerging schistosomiasis have not been completely eliminated, such as residual snails and imported schistosomiasis cases. Further surveillance and control activities of snails and the source of S. japonicum infections should be reinforced.