Sensitive and rapid detection of Schistosoma japonicum DNA by loop-mediated isothermal amplification (LAMP)

Low schistosomiasis and soil-transmitted helminthiasis prevalence and intensities in selected communities in Davao de Oro and Davao del Norte, the Philippines: A setting for interruption of transmission?

Parasitic neglected tropical diseases, such as schistosomiasis and soil-transmitted helminthiasis (STH), remain as significant public health concerns in developing countries such as the Philippines. This study aimed to determine the prevalence and intensity of schistosomiasis and STH among school-age children (SAC) and adults in two co-endemic provinces in Mindanao in southern Philippines as part of monitoring of national control programs. Stool samples were collected, processed using Kato-Katz technique, and examined microscopically for presence of intestinal helminth ova. A total of 776 SAC and 526 adults participated in the study. Low schistosomiasis prevalence was generally observed in SAC (0.8%) and adults (0.4%). Generally low STH prevalence was reported in both SAC (3.9%) and adults (3.4%). Only three SAC had heavy intensity STH, which was not seen in adults. Results indicate a state of good morbidity control, which may be a result of effective implementation of mass drug administration (MDA) strategy for schistosomiasis, STH, and lymphatic filariasis in the last several years. The low prevalence and intensities of infections may also be partly attributed to the low diagnostic sensitivity of Kato-Katz technique in detecting low intensity intestinal helminth infections. While results of this study also indicate similarly low levels of both these infections in previous studies, sustaining high MDA coverage rates and addressing remaining challenges related to intensified case finding and treatment, improvements in safe water, sanitation, and hygiene, veterinary public health, and vector ecology and management will be necessary to interrupt transmission in these areas.

Detection of Parasites in the Field: The Ever-Innovating CRISPR/Cas12a

The rapid and accurate identification of parasites is crucial for prompt therapeutic intervention in parasitosis and effective epidemiological surveillance. For accurate and effective clinical diagnosis, it is imperative to develop a nucleic-acid-based diagnostic tool that combines the sensitivity and specificity of nucleic acid amplification tests (NAATs) with the speed, cost-effectiveness, and convenience of isothermal amplification methods. A new nucleic acid detection method, utilizing the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) nuclease, holds promise in point-of-care testing (POCT). CRISPR/Cas12a is presently employed for the detection of Plasmodium falciparum, Toxoplasma gondii, Schistosoma haematobium, and other parasites in blood, urine, or feces. Compared to traditional assays, the CRISPR assay has demonstrated notable advantages, including comparable sensitivity and specificity, simple observation of reaction results, easy and stable transportation conditions, and low equipment dependence. However, a common issue arises as both amplification and cis-cleavage compete in one-pot assays, leading to an extended reaction time. The use of suboptimal crRNA, light-activated crRNA, and spatial separation can potentially weaken or entirely eliminate the competition between amplification and cis-cleavage. This could lead to enhanced sensitivity and reduced reaction times in one-pot assays. Nevertheless, higher costs and complex pre-test genome extraction have hindered the popularization of CRISPR/Cas12a in POCT.

Diagnostic Efficacy of Plasma-Based Real-Time PCR for Schistosomiasis Japonica in Mice before and after Treatment with Praziquantel

The prevalence of schistosomiasis japonica in China is now characterized by a low epidemic rate and low-intensity infections. Some diagnostic methods with high sensitivity and specificity are urgently needed to better monitor this disease in the current situation. In this study, the detection efficacy of a real-time fluorescent quantitative PCR (qPCR) assay was assessed for schistosomiasis japonica in mice, and before and after treatment with praziquantel (PZQ). Our results showed that the sensitivity of the qPCR was 99.3% (152/153, 95% CI: 96.41-99.98%) and its specificity was 100% (77/77, 95% CI: 95.32-100%) in mice infected with different numbers of Schistosoma japonicum. After the oral administration of PZQ, mice infected with 10 cercariae or 40 cercariae were all Schistosoma japonicum-negative 6 weeks after treatment. However, the negativity rates on a soluble egg antigen (SEA)-based enzyme-linked immunosorbent assay (ELISA) were only 34.8% (8/23, 10 cercariae group) and 6.7% (1/15, 40 cercariae group) at the sixth week after PZQ treatment. These results demonstrated that the qPCR method had good sensitivity and specificity, and suggested that its sensitivity correlated with the infection intensity in mice. Moreover, this method had better potential utility for evaluating the treatment efficacy of PZQ in schistosome-infected mice than SEA-based ELISA.

Metagenomic sequencing for identifying pathogen-specific circulating DNAs and development of diagnostic methods for schistosomiasis

Timely diagnosis of Schistosoma infection, particularly in the early stage is crucial for identifying infected hosts and then taking effective control strategies. Here, metagenomic next-generation sequencing was used to identify pathogen-specific circulating DNAs (cDNAs) in the sera/plasma of New Zealand rabbits infected with S. japonicum, and the identified cDNAs were validated by PCR and qPCR. Loop-mediated isothermal amplification (LAMP)-based CRISPR-Cas12a and recombinase polymerase amplification-based lateral flow strip (RPA-LF) methods combined with the newly identified cDNA were developed to evaluate the potentials for diagnosing murine and human schistosomiasis. The results indicated that twenty-two cDNAs were identified. The developed LAMP-based CRISPR/Cas12a and RPA-LF methods showed a good potential for diagnosing murine or human schistosomiasis as early as 5 days of post-infection with 5 cercariae infection. In a word, S. japonicum specific cDNAs in circulation of infected hosts could be effective biomarkers for detecting Schistosoma infection particularly for early stages.

Two Molecular Plasma-Based Diagnostic Methods to Evaluate Early Infection of Schistosoma japonicum and Schistosomiasis Japonica

The prevalence and infectious intensity of schistosomiasis japonica has decreased significantly in China in the past few decades. However, more accurate and sensitive diagnostic methods are urgently required for the further control, surveillance, and final elimination of the disease. In this study, we assessed the diagnostic efficacy of a real-time fluorescence quantitative PCR (qPCR) method and recombinase polymerase amplification (RPA) combined with a lateral-flow dipstick (LFD) assay for detecting early infections of Schistosoma japonicum and different infection intensities. The sensitivity of the qPCR at 40 days post-infection (dpi) was 100% (8/8) in mice infected with 40 cercariae, which was higher than in mice infected with 10 cercariae (90%, 9/10) or five cercariae (77.8%, 7/9). The results of the RPA-LFD assays were similar, with sensitivities of 55.6% (5/9), 80% (8/10), and 100% (8/8) in mice infected with 5, 10, and 40 cercariae, respectively. In goats, both the qPCR and RPA-LFD assays showed 100% (8/8) sensitivity at 56 dpi. In the early detection of S. japonicum infection in mice and goats with qPCR, the first peak in positivity appeared at 3-4 dpi, when the positivity rate exceeded 40%, even in the low infection, intensity mice. In the RPA-LFD assays, positive results first peaked at 4-5 dpi in the mice, and the positivity rate was 37.5% in the goats at 1 dpi. In conclusion, neither of the molecular methods produced exceptional results for the early diagnosis of S. japonicum infection. However, they were useful methods for the regular diagnosis of schistosomiasis in mice and goats.

Geographical distribution and molecular survey of freshwater snail intermediate hosts of Schistosoma haematobium by DraI/Sh73 PCR in eliminated foci of Morocco

Morocco had reached the level of schistosomiasis elimination 16 years ago. However the spread of freshwater snails in several breeding sites, and imported schistosome infection, still exist. Therefore, snail survey is a crucial component to sustain elimination progress. This study aimed to evaluate and to incorporate DraI/Sh73 PCR, for detecting early prepatent Schistosoma haematobium infection in snail host, into epidemiologic surveillance for schistosomiasis, particularly in reportedly eliminated foci where S.bovis overlaps with S. haematobium. The geographical distribution and the density of Bulinus truncatus and Planorbarius metidjensis were monitored for six years (2014-2019) and snail sampling were conducted in Fkih Ben Saleh province. All snails were analyzed in pools by DraI/Sh73 PCR. Results showed absence of Planorbarius metidjensi and none of the collected Bulinus truncatus snails were infected by S. haematobium. DraI/Sh73 PCR using pooled snail extracts is specific, feasible and suitable in routine malacological survey in the post elimination phase of schistosomiasis in Morocco.

The Efficiency of Commercial Immunodiagnostic Assays for the Field Detection of Schistosoma japonicum Human Infections: A Meta-Analysis

Although great strides have been achieved, schistosomiasis japonica remains a major public health concern in China. Immunodiagnostics have been widely accepted as the first choice in large-scale screening of Schistosoma japonicum human infections, and indirect hemagglutination test (IHA), enzyme-linked immunosorbent assay (ELISA), and dipstick dye immunoassay (DDIA) are currently the three most common immunological tests for the diagnosis of S. japonicum human infections in China. This meta-analysis aimed to comprehensively assess the performance of IHA, ELISA, and DDIA for the field diagnosis of S. japonicum human infections. A total of 37 eligible publications were enrolled in the final analysis, including 29 Chinese publications and 8 English publications. No significant heterogeneities were detected among the studies reporting ELISA (I2 = 88%, p < 0.05), IHA (I2 = 95%, p < 0.05), or DDIA (I2 = 84%, p < 0.05). DDIA showed the highest pooled sensitivity (90.8%, 95% CI: 84.6% to 94.7%) and IHA presented the highest pooled specificity for detection of S. japonicum human infections (71.6%, 95% CI: 65.9% to 76.7%). Summary receiver operating characteristic (SROC) curve analysis showed that IHA exhibited the highest area under the SROC curve (AUC) (0.88, 95% CI: 0.85 to 0.9), and ELISA presented the lowest AUC (0.85, 95% CI: 0.82 to 0.88). Deeks’ funnel plots indicated no publication bias. IHA presented the highest sensitivity in medium-endemicity regions and the highest specificity for diagnosis of S. japonicum human infections in low-endemicity regions, and ELISA showed the highest diagnostic sensitivity in high-endemicity regions and the highest specificity in medium-endemicity regions, while DDIA exhibited the highest diagnostic sensitivity in high-endemicity regions and the highest specificity in low-endemicity regions. IHA and DDIA presented a higher efficiency for the diagnosis of S. japonicum human infections in marshland and lake regions than in hilly and mountainous regions, while ELISA showed a comparable diagnostic sensitivity between in marshland and lake regions and hilly and mountainous regions (88.3% vs. 88.6%), and a higher specificity in marshland and lake regions than in hilly and mountainous regions (60% vs. 48%). Our meta-analysis demonstrates a comparable diagnostic accuracy of IHA, ELISA, and DDIA for S. japonicum human infections, and the diagnostic sensitivity and specificity of IHA, ELISA, and DDIA vary in types and infection prevalence of endemic regions. DDIA combined with IHA is recommended as a tool for screening chemotherapy targets and seroepidemiological surveys during the stage moving towards schistosomiasis elimination in China. Further studies to examine the effectiveness of combinations of two or three immunological tests for diagnosis of S. japonicum human infections are warranted.

Schistosomiasis related circulating cell-free DNA: A useful biomarker in diagnostics

Schistosoma is a genus of trematodes causing schistosomiasis, a major neglected tropical disease infecting more than 240 million people and with 700 million people at the risk of infection in the tropical and subtropical regions of the world, especially low-income countries. For the elimination of the disease, accurate diagnostic tools are needed. Besides allowing early treatment, early detection prevents environmental contamination and in turn ensures safe water sources in the endemic areas. Cell-free DNA (cfDNA) biomarker detection is a relatively new tool, used for the diagnosis of schistosomiasis in the early stages of infection from non-invasive clinical or experimental samples. cfDNA can be detected in Schistosoma infected host body fluids such as urine, serum, saliva and tissues, mainly in blood offering significant benefits for accurate diagnosis. In the current review, we described different characteristics of cfDNA, evidencing and supporting its potential uses in Schistosoma diagnosis and the improvement of treatment effectiveness.

Evaluation of loop-mediated isothermal amplification assay and enzyme-linked immunosorbent assay in detecting Schistosoma japonicum in Siargao Island, Surigao del Norte, the Philippines

OBJECTIVES

This study aimed to describe the prevalence and seroprevalence of schistosomiasis in Siargao Island, Surigao del Norte and to compare the performance of enzyme-linked immunosorbent assay antibody test (ELISA Ab) and loop-mediated isothermal amplification assay (LAMP) for diagnosis of schistosomiasis.

METHODS

The study was conducted in selected barangays (villages) in five municipalities in Siargao Island, Surigao del Norte and included school-age children (SAC) who submitted stool and blood samples. Stool samples were examined using the Kato-Katz technique. Blood samples were collected through venipuncture. The stool samples and the blood samples collected were tested using LAMP assay and polymerase chain reaction (PCR). The blood samples were examined using ELISA Ab. Diagnostic performance of LAMP assay using stool specimen was evaluated using Kato-Katz technique and PCR assay as the composite reference standard, while PCR assay was used as the reference standard to evaluate LAMP assay and ELISA Ab using blood specimens.

RESULTS

A total of 417 stool samples from SAC were examined. The prevalence of schistosomiasis and moderate-heavy intensity (MHI) schistosomiasis were 3.8% and 1.4%, respectively. Schistosomiasis and soil-transmitted helminthiases (STH) coinfection prevalence were 2.6%. A total of 425 blood samples were examined using ELISA Ab. Seroprevalence was 61.6%. The municipality of San Isidro had the highest seroprevalence at 84.8%, while Burgos had the lowest seroprevalence at 48.5%.LAMP assay had higher sensitivity and positive predictive value but lower specificity when using stool than when using blood samples. Its negative predictive value was similar regardless of the specimen used. ELISA Ab has higher sensitivity and negative predictive value than LAMP assay although it has lower specificity and positive predictive value. This may be due to ELISA Ab measuring Schistosoma exposure and is thus unable to distinguish past from active infection.

CONCLUSIONS

Schistosomiasis remains a public health concern in Siargao Island, Surigao del Norte. The locally developed LAMP assay offers a simpler diagnostic test for schistosomiasis compared with PCR, while minimizing the risk of misdiagnosis compared with Kato-Katz technique. It could serve as a point of care diagnostics for schistosomiasis. ELISA Ab is more useful in surveillance particularly in low-endemicity areas where determination of exposure is more important than differentiating past from active infection. ELISA Ab may be helpful in the clinical setting when coupled with the expertise of a physician who is familiar with schistosomiasis.

Molecular Techniques as Alternatives of Diagnostic Tools in China as Schistosomiasis Moving towards Elimination

Schistosomiasis japonica caused by the trematode flukes of Schistosoma japonicum was one of the most grievous infectious diseases in China in the mid-20th century, while its elimination has been placed on the agenda of the national strategic plan of healthy China 2030 after 70 years of continuous control campaigns. Diagnostic tools play a pivotal role in warfare against schistosomiasis but must adapt to the endemic status and objectives of activities. With the decrease of prevalence and infection intensity of schistosomiasis in human beings and livestock, optimal methodologies with high sensitivity and absolute specificity are needed for the detection of asymptomatic cases or light infections, as well as disease surveillance to verify elimination. In comparison with the parasitological methods with relatively low sensitivity and serological techniques lacking specificity, which both had been widely used in previous control stages, the molecular detection methods based on the amplification of promising genes of the schistosome genome may pick up the baton to assist the eventual aim of elimination. In this article, we reviewed the developed molecular methods for detecting S. japonicum infection and their application in schistosomiasis japonica diagnosis. Concurrently, we also analyzed the chances and challenges of molecular tools to the field application process in China.

The status of schistosomiasis japonica control in the Philippines: The need for an integrated approach to address a multidimensional problem

Schistosomiasis japonica remains a public health concern in many areas of the Philippines. Adequate and updated information is essential to enhance policy and service delivery toward control and elimination. Despite the efforts on schistosomiasis control in the Philippines, some challenges remain in these dimensions. An integrated surveillance system is recommended to determine the prevalence of infection in humans, animal reservoirs, and snail intermediate hosts, allowing the identification of high-priority areas for targeted interventions. This will entail the enhancement of laboratory diagnosis capacity through the use of more sensitive techniques, complemented by capacity building of concerned human and animal health professionals. Given the zoonotic nature of schistosomiasis japonica, adopting the One Health approach is essential to influence policies and interventions that may accelerate control and elimination. This can be achieved through the attainment of mass drug administration coverage targets and intensified case finding and management, robust implementation and integration of veterinary public health activities, the conduct of snail control measures, provision of safe water, sanitation, and hygiene services, and health promotion and education into the national schistosomiasis control and elimination program. This review aimed to describe the status of schistosomiasis japonica control in the Philippines in the context of human health, animal health, vector ecology and management, environmental health, and sociocultural dimensions.

Development of New Technologies for Risk Identification of Schistosomiasis Transmission in China

Schistosomiasis is serious parasitic disease with an estimated global prevalence of active infections of more than 190 million. Accurate methods for the assessment of schistosomiasis risk are crucial for schistosomiasis prevention and control in China. Traditional approaches to the identification of epidemiological risk factors include pathogen biology, immunology, imaging, and molecular biology techniques. Identification of schistosomiasis risk has been revolutionized by the advent of computer network communication technologies, including 3S, mathematical modeling, big data, and artificial intelligence (AI). In this review, we analyze the development of traditional and new technologies for risk identification of schistosomiasis transmission in China. New technologies allow for the integration of environmental and socio-economic factors for accurate prediction of the risk population and regions. The combination of traditional and new techniques provides a foundation for the development of more effective approaches to accelerate the process of schistosomiasis elimination.

Meta-analysis of variable-temperature PCR technique performance for diagnosising Schistosoma japonicum infections in humans in endemic areas

BACKGROUND

As China is moving onto schistosomiasis elimination/eradication, diagnostic methods with both high sensitivity and specificity for Schistosoma japonicum infections in humans are urgently needed. Microscopic identification of eggs in stool is proven to have poor sensitivity in low endemic regions, and antibody tests are unable to distinguish between current and previous infections. Polymerase chain reaction (PCR) technologies for the detection of parasite DNA have been theoretically assumed to show high diagnostic sensitivity and specificity. However, the reported performance of PCR for detecting S. japonicum infection varied greatly among studies. Therefore, we performed a meta-analysis to evaluate the overall diagnostic performance of variable-temperature PCR technologies, based on stool or blood, for detecting S. japonicum infections in humans from endemic areas.

METHODS

We searched literatures in eight electronic databases, published up to 20 January 2021. The heterogeneity and publication bias of included studies were assessed statistically. The risk of bias and applicability of each eligible study were assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 tool (QUADAS-2). The bivariate mixed-effects model was applied to obtain the summary estimates of diagnostic performance. The hierarchical summary receiver operating characteristic (HSROC) curve was applied to visually display the results. Subgroup analyses and multivariate regression were performed to explore the source of heterogeneity. This research was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and was registered prospectively in PROSPERO (CRD42021233165).

RESULTS

A total of 2791 papers were retrieved. After assessing for duplications and eligilibity a total of thirteen publications were retained for inclusion. These included eligible data from 4268 participants across sixteen studies. High heterogeneity existed among studies, but no publication bias was found. The pooled analyses of PCR data from all included studies resulted in a sensitivity of 0.91 (95% CI: 0.83 to 0.96), specificity of 0.85 (95% CI: 0.65 to 0.94), positive likelihood ratio of 5.90 (95% CI: 2.40 to 14.60), negative likelihood ratio of 0.10 (95% CI: 0.05 to 0.20) and a diagnostics odds ratio of 58 (95% CI: 19 to 179). Case-control studies showed significantly better performances for PCR diagnostics than cross-sectional studies. This was further evidenced by multivariate analyses. The four types of PCR approaches identified (conventional PCR, qPCR, Droplet digital PCR and nested PCR) differed significantly, with nested PCRs showing the best performance.

CONCLUSIONS

Variable-temperature PCR has a satisfactory performance for diagnosing S. japonicum infections in humans in endemic areas. More high quality studies on S. japonicum diagnostic techniques, especially in low endemic areas and for the detection of dual-sex and single-sex infections are required. These will likely need to optimise a nested PCR alongside a highly sensitive gene target. They will contribute to successfully monitoring endemic areas as they move towards the WHO 2030 targets, as well as ultimately helping areas to achieve these goals.

Development of a loop-mediated isothermal amplification assay for detection of Austropeplea tomentosa from environmental water samples

Lymnaeid snails are key intermediate hosts for the development and survival of Fasciola spp., the causative agent of Fascioliasis which are economically important parasites infecting humans and livestock globally. The current control method for treating Fascioliasis is heavily reliant on anthelmintic drugs, particularly Triclabendazole (TCBZ) which has resulted in drug-resistant parasites and poses significant risk as there are no long-term efficacious alternatives available. Sustainable control measures at the farm level could include both parasite and snail control will play an important role in Fasciola spp. control and reduce the reliance on anthelmintic drugs. Implementation of such sustainable control measures requires effective identification of snails on the property however Lymnaeid snails are small and difficult to physically locate. Snail identification using an environmental DNA approach is a recent approach in which physically locating snails are not required. Austropeplea tomentosa, is the primary intermediate snail host for F. hepatica transmission in South-East Australia and we present an in-field loop-mediated isothermal amplification and water filtering method for the detection of A. tomentosa eDNA from water samples to improve current surveillance methods. This methodology is highly sensitive with a detection limit of 5 × 10^− 6 ng/μL, detected in < 20 minutes, with cumulative sample preparation and amplification time under 1 hour. This proposed workflow could assist in monitoring areas to determine the risk of Fascioliasis infection and implement strategies to manage snail populations to ultimately reduce the risk of infection for humans and livestock.

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.

Toxocara Species Infection in Pet Dogs and Cats Ensured by Loop-Mediated Isothermal Amplification Assay

Background: Toxocariasis is a parasitic disease with global distribution. Many paratenic or transport hosts have been identified as the sources of infection, including vertebrates such as birds and humans. The definitive hosts of Toxocara are dogs and cats whose parasites live in their guts. Hence, the diagnosis of the disease in these animals is important. Objective: The present study was performed using the loop-mediated isothermal amplification (LAMP) method to diagnose toxocariasis. Materials and Methods: In the present study, 60 samples of pet feces were collected and subsequently evaluated by direct smear, formalin-ether, and LAMP. Results: Toxocara infection in dogs by microscopic and formal ether methods and LAMP method was 10% and 13.3%, respectively, while feline infection with this parasite was not observed either microscopically or molecularly. Conclusion: The present findings revealed that pet dogs can be considered as a source of infection for humans. Therefore, it is recommended that animal owners receive the necessary training to prevent the risks of transmitting zoonotic diseases.

Low Sensitivity of Real Time PCRs Targeting Retrotransposon Sequences for the Detection of Schistosoma japonicum Complex DNA in Human Serum

While hybridization probe-based real-time PCR assays targeting highly repetitive multi-copy genome sequences for the diagnosis of S. mansoni complex or S. haematobium complex from human serum are well established, reports on the evaluation of respective assays for the identification of S. japonicum complex DNA in human serum are scarce. Here, we assessed the potential use of the retrotransposon sequences SjR2 and SjCHGCS19 from S. japonicum, S. mekongi and S. malayensis for the diagnosis of Asian Schistosoma infections. Based on available S. japonicum sequences and newly provided S. mekongi and S. malayensis sequences, hybridization probe-based real-time PCRs targeting SjR2 and SjCHGCS19 of the S. japonicum complex were designed both as consensus primer assays as well as multi-primer assays for the coverage of multiple variants of the target sequences. The assays were established using plasmids and S. mekongi DNA. While the consensus primer assays failed to detect S. mekongi DNA in human serum samples, the multi-primer assays showed positive or borderline positive results but only in 9.8% (6/61) of serum samples from patients with confirmed S. mekongi infections. Some cross-reactions with samples positive for S. mansoni or S. haematobium were observed but with the SjCHGCS19-PCR only. In spite of the low sensitivity, the presented experience may guide future evaluations of S. japonicum-complex-specific PCRs from human serum.

LAMP Assay for the Detection of Echinococcus multilocularis Eggs Isolated from Canine Faeces by a Cost-Effective NaOH-Based DNA Extraction Method

The detection of Echinococcus multilocularis in infected canids and the environment is pivotal for a better understanding of the epidemiology of alveolar echinococcosis in endemic areas. Necropsy/sedimentation and counting technique remain the gold standard for the detection of canid infection. PCR-based detection methods have shown high sensitivity and specificity, but they have been hardly used in large scale prevalence studies. Loop-mediated isothermal amplification (LAMP) is a fast and simple method to detect DNA with a high sensitivity and specificity, having the potential for field-application. A specific LAMP assay for the detection of E. multilocularis was developed targeting the mitochondrial nad1 gene. A crucial step for amplification-based detection methods is DNA extraction, usually achieved utilising silica-gel membrane spin columns from commercial kits which are expensive. We propose two cost-effective and straightforward methods for DNA extraction, using NaOH (method 1A) and InstaGene^TM Matrix (method 1B), from isolated eggs circumventing the need for commercial kits. The sensitivity of both assays with fox samples was similar (72.7%) with multiplex-PCR using protocol 1A and LAMP using protocol 1B. Sensitivity increased up to 100% when testing faeces from 12 foxes infected with more than 100 intestinal stages of E. multilocularis. For dogs, sensitivity was similar (95.4%) for LAMP and multiplex-PCR using protocol 1B and for both methods when DNA was extracted using protocol 1A (90.9%). The DNA extraction methods used here are fast, cheap, and do not require a DNA purification step, making them suitable for field studies in low-income countries for the prevalence study of E. multilocularis.

LAMP in Neglected Tropical Diseases: A Focus on Parasites

Neglected Tropical Diseases (NTDs), particularly those caused by parasites, remain a major Public Health problem in tropical and subtropical regions, with 10% of the world population being infected. Their management and control have been traditionally hampered, among other factors, by the difficulty to deploy rapid, specific, and affordable diagnostic tools in low resource settings. This is especially true for complex PCR-based methods. Isothermal nucleic acid amplification techniques, particularly loop-mediated isothermal amplification (LAMP), appeared in the early 21st century as an alternative to PCR, allowing for a much more affordable molecular diagnostic. Here, we present the status of LAMP assays development in parasite-caused NTDs. We address the progress made in different research applications of the technique: xenomonitoring, epidemiological studies, work in animal models and clinical application both for diagnosis and evaluation of treatment success. Finally, we try to shed a light on the improvements needed to achieve a true point-of-care test and the future perspectives in this field.

Accurate and rapid detection of Fasciola hepatica copro-DNA in sheep using loop-mediated isothermal amplification (LAMP) technique

Fascioliasis is a parasitic infection caused by Fasciola spp. in humans and animals. Despite significant advances in vaccination and new therapeutic agents, little attention has been paid to validate methods for the diagnosis of fascioliasis in animals. This study aimed to compare the loop‐mediated isothermal amplification (LAMP) technique with PCR assay for the diagnosis of F. hepatica in sheep. In this cross‐sectional study, 195 stool samples were collected from sheep for 3 months in Lorestan province, West of Iran. Specimens’ parasitological examination was performed by using the direct wet mount and formalin‐ether concentration method. After DNA extraction from the samples, molecular analysis was done using PCR and LAMP techniques based on the Fasciola ribosomal intergenic spacer (IGS) sequence. Of 195 specimens of sheep, 11 specimens were identified as F. hepatica‐positive infection by using microscopic, PCR and LAMP assays. Kappa agreement test results showed that there was a significant agreement between the results of microscopic examination diagnostic tests, PCR and LAMP (Kappa = 0.51–0.72 and p < .001). According to the results of chi‐square comparisons between parasite prevalence applying different techniques and variables of age, sex breed, and type of drinking water, there was no significant relationship (p ≥ .05). However, most of the infected sheep with Fasciola were 3‐ to 4‐year‐old females, of the Lori breed and consumed tap water. In many endemic areas, successful prevention and treatment of fascioliasis in animals depend on rapid and accurate diagnosis. Based on the results of the Kappa agreement, the significant agreement among the results of the microscopic examination, PCR and LAMP indicates the accuracy and reliability of these tests in the diagnosis of F. hepatica in sheep. However, molecular methods, especially the LAMP technique, are suggested because of their higher sensitivity and reliability for the diagnosis of F. hepatica even under field conditions.

Loop-Mediated Isothermal Amplification in Schistosomiasis

Human schistosomiasis is one of the most important parasitic diseases, causing around 250 million cases (mostly in Africa) and 280,000–500,000 deaths every year. Due to the limited resources and the far-removed nature of many endemic areas, the implementation of new, sensitive and specific diagnostic tools has had little success. This is particularly true for PCR-based molecular methods that require expensive equipment and trained personnel to be executed. Loop-mediated isothermal amplification (LAMP) along with other isothermal techniques appeared in the early 21st century as an alternative to those methods, overcoming some of the aforementioned limitations and achieving a more inexpensive diagnostic. However, to this date, neither LAMP nor any other isothermal technique have signified a meaningful change in the way schistosomiasis diagnosis is routinely performed. Here, we present the recent developments in LAMP-based schistosomiasis diagnosis. We expose the main advantages and disadvantages of LAMP technology over PCR and other classical diagnostic methods focusing in various research approaches on intermediate hosts, animal models and patients. We also examine its potential clinical application in post-therapy monitoring, as well as its usefulness as a point-of-care test.

Reviews and advances in diagnostic research on Schistosoma japonicum

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. Schistosoma japonicum (S. japonicum) infection has decreased significantly in prevalence and intensity of infection in China. However, this disease still remains a serious public health problem in some endemic areas of the Philippines and Indonesia. Thus, more accurate and sensitive methods are much needed for further control of this disease. Here, we review the research progress in techniques for the diagnosis of S. japonicum infection.

Circulating cell-free mitochondrial DNA fragment: A possible marker for early detection of Schistosoma japonicum

Schistosomiasis is a major public health problem that is included in the neglected tropical diseases. The early diagnosis and detection of the pathogen are of critical importance in the control of the disease. The diagnostic techniques in use include the detection of worm's eggs in fecal examination or detection of circulating antigens in immunological based assays. These traditional strategies lack sensitivity in earlier detection of the schistosomiasis. Cell-free DNA (cfDNA) that includes the fragments of parasitic DNA circulating in the body fluids of host offers an alternative mean for the rapid pathogen detection and thus is a useful diagnostic tool. In this study, we explored the usefulness of the mitochondrial cfDNA markers for the diagnosis of schistosomiasis from the experimentally infected hosts (rabbits and mice). In this study we found mitochondrial DNA fragment cytochrome B gene as persistent and useful cfDNA marker for the early detection of schistosomiasis. We evaluated the sensitivity of cfDNA marker with varying numbers of cercaria. Overall, our results suggest that cfDNA markers can be useful for developing a diagnostic tool for the detection of S. japonicum infection.

Detection of circulating cell-free DNA to diagnose Schistosoma japonicum infection

Schistosomiasis occurs in 240 million people worldwide and is a major public health concern. Thus, early diagnosis and monitoring of schistosomiasis progression are needed to treat patients. Cell-free DNA (cfDNA) is present as fragments of parasite-derived DNA in host body fluids. Detection of this cfDNA in host blood may be a promising diagnostic marker of schistosomiasis. Therefore, in this study, we investigated the potential of internal transcribed spacer 2 (ITS2), a molecular taxonomy and barcoding marker, in diagnosing schistosomiasis using infected rabbit and mice sera. A 192 bp fragment of ITS2 was detected in the serum-isolated DNA from the infected host on different days after infection. We also determined the sensitivity of detecting ITS2 in mice with varying numbers of cercaria: cfDNA was present even in mice with low abundance of the parasite. Overall, our results show that cfDNA may be a potential tool for the early diagnosis and therapeutic evaluation of S. japonicum infection.

Loop-Mediated Isothermal Amplification as Point-of-Care Diagnosis for Neglected Parasitic Infections

The World Health Organisation (WHO) has placed twenty diseases into a group known as neglected tropical diseases (NTDs), twelve of them being parasitic diseases: Chagas’ disease, cysticercosis/taeniasis, echinococcosis, food-borne trematodiasis, human African trypanosomiasis (sleeping sickness), leishmaniasis, lymphatic filariasis, onchocerciasis (river blindness), schistosomiasis, soil-transmitted helminthiasis (ascariasis, hookworm, trichuriasis), guinea-worm and scabies. Such diseases affect millions of people in developing countries where one of the main problems concerning the control of these diseases is diagnosis-based due to the most affected areas usually being far from laboratories having suitable infrastructure and/or being equipped with sophisticated equipment. Advances have been made during the last two decades regarding standardising and introducing techniques enabling diagnoses to be made in remote places, i.e., the loop-mediated isothermal amplification (LAMP) technique. This technique’s advantages include being able to perform it using simple equipment, diagnosis made directly in the field, low cost of each test and the technique’s high specificity. Using this technique could thus contribute toward neglected parasite infection (NPI) control and eradication programmes. This review describes the advances made to date regarding LAMP tests, as it has been found that even though several studies have been conducted concerning most NPI, information is scarce for others.

A DNA molecular diagnostic technology with LAMP-like sensitivity based on one pair of hairpin primers-mediated isothermal polymerization amplification

With the rapid development of isothermal amplification technology, DNA molecular diagnosis has become an important reference for clinical treatment. In this work, we have designed a DNA molecular diagnostic technology with LAMP-like sensitivity for nucleic acid analysis and detection based on only one pair of hairpin primers. This DNA molecular diagnostic technology consists of Bst DNA polymerase and one pair of hairpin primers, which are designed easily by adding a stem-loop structure to a target binding domain. When the target is present, the polymerization reaction between the hairpin primers and the target generates a specific dumbbell DNA similar to LAMP, which triggers cyclic amplification reactions to extend a series of long dsDNA products with repeated sequences by inserting fluorescent dye Eva Green observed the increase in fluorescence signal. In our method, using the hairpin primers-mediated isothermal polymerization amplification, we can specifically monitor 3-5 copies of the target nucleic acid in the system without labeling and temperature cycling in the reaction. In addition, serum samples from 13 patients with suspected schistosomiasis were targeted; we further demonstrated the ability of the technology to detect complex clinic samples, and its potentially inestimable applicability in clinic early molecular diagnostic research.

Sensitive diagnostic tools and targeted drug administration strategies are needed to eliminate schistosomiasis

Although preventive chemotherapy has been instrumental in reducing schistosomiasis incidence worldwide, serious challenges remain. These problems include the omission of certain groups from campaigns of mass drug administration, the existence of persistent disease hotspots, and the risk of recrudescent infections. Central to these challenges is the fact that the diagnostic tools currently used to establish the burden of infection are not sensitive enough, especially in low-endemic settings, which results in underestimation of the true prevalence of active Schistosoma spp infections. This central issue necessitates that the current schistosomiasis control strategies recommended by WHO are re-evaluated and, possibly, adapted. More targeted interventions and novel approaches have been used to estimate the prevalence of schistosomiasis, such as establishing infection burden by use of precision mapping, which provides high resolution spatial information that delineates variations in prevalence within a defined geographical area. Such information is instrumental in guiding targeted intervention campaigns. However, the need for highly accurate diagnostic tools in such strategies is a crucial factor that is often neglected. The availability of highly sensitive diagnostic tests also opens up the possibility of applying strategies of sample pooling to reduce the cost of control programmes. To interrupt the transmission of, and eventually eliminate, schistosomiasis, better local targeting of preventive chemotherapy, in combination with highly sensitive diagnostic tools, is crucial.

Schistosomiasis: from established diagnostic assays to emerging micro/nanotechnology-based rapid field testing for clinical management and epidemiology

Schistosomiasis is a neglected invasive worm disease with a huge disease burden in developing countries, particularly in children, and is seen increasingly in non-endemic regions through transfer by travellers, expatriates, and refugees. Undetected and untreated infections may be responsible for the persistence of transmission. Rapid and accurate diagnosis is the key to treatment and control. So far, parasitological detection methods remain the cornerstone of Schistosoma infection diagnosis in endemic regions, but conventional tests have limited sensitivity, in particular in low-grade infection. Recent advances contribute to improved detection in clinical and field settings. The recent progress in micro- and nanotechnologies opens a road by enabling the design of new miniaturized point-of-care devices and analytical platforms, which can be used for the rapid detection of these infections. This review starts with an overview of currently available laboratory tests and their performance and then discusses emerging rapid and micro/nanotechnologies-based tools. The epidemiological and clinical setting of testing is then discussed as an important determinant for the selection of the best analytical strategy in patients suspected to suffer from Schistosoma infection. Finally, it discusses the potential role of advanced technologies in the setting near to disease eradication is examined.

Recent advances in nucleic acid-based methods for detection of helminth infections and the perspective of biosensors for future development

Pathogenic helminth infections are responsible for severe health problems and economic losses worldwide. Timely and accurate diagnosis of helminth infections is critical for adopting suitable strategies for pathogen control. Here, we review recent advances in nucleic acid-based diagnostic methods, including polymerase chain reaction, quantitative qPCR, loop-mediated isothermal amplification and recombinase polymerase amplification, and discuss their advantages and disadvantages for diagnosing helminth infections. In addition, we highlight recent advances in biosensors for the detection of nucleic acid biomarkers that can potentially be used for the diagnosis of helminth infection.

Sensitive and rapid detection of Ortleppascaris sinensis (Nematoda: Ascaridoidea) by loop-mediated isothermal amplification

Ortleppascaris sinensis is the dominant nematode species infecting the gastrointestinal tract of the captive Chinese alligator, a critically endangered species. Gastrointestinal nematode infection may cause a loss of appetite, growth, a development disorder, and even mortality in alligators, especially young ones. This research first establishment a loop-mediated isothermal amplification (LAMP) assay in rapidly identifying O. sinensis, upon the basis of the complete internal transcribed spacers (ITS) gene. Eight sets of primers were designed for recognition of the unique conserved ITS gene sequences, and one set was selected to be the most suitable primer for rapid detection. The specific as well as the sensitive features of the most appropriate primer in LAMP reactions for O. sinensis, and feces specimens of Chinese alligators suffering from O. sinensis were determined. Turbidity monitoring and Te Visual Reagent methods were used for determining negative and positive consequences. According to this study, amplification and visualization of the target DNA could be realized through two detection approaches during 50 min at 65 °C isothermal temperature. The sensitivity of LAMP was a detecting limitation of 3.46 pg/µl DNA. No cross-reactions were found between O. sinensis and any other of the nine heterologous nematode parasites, which shows the outstanding specific features of the primers. The LAMP assay could also perform a detection of target DNA of O. sinensis in the feces samples of Chinese alligators. This LAMP assay is useful for directly detecting O. sinensis in the Chinese alligator breeding centers, particularly due to its rapidity, simplicity and low cost.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Spirorchiidiasis in marine turtles: the current state of knowledge

Blood flukes of the family Spirorchiidae are important disease agents in marine turtles. The family is near cosmopolitan in distribution. Twenty-nine marine species across 10 genera are currently recognized, but taxonomic problems remain and it is likely that more species will be discovered. Spirorchiids infect the circulatory system, where they and their eggs cause a range of inflammatory lesions. Infection is sometimes implicated in the death of the turtle. In some regions, prevalence in stranded turtles is close to 100%. Knowledge of life cycles, important for control and epidemiological studies, has proven elusive until recently, when the first intermediate host identifications were made. Recent molecular studies of eggs and adult worms indicate that a considerable level of intrageneric and intraspecific diversity exists. The characterization of this diversity is likely to be of importance in exploring parasite taxonomy and ecology, unravelling life cycles, identifying the differential pathogenicity of genotypes and species, and developing antemortem diagnostic tools, all of which are major priorities for future spirorchiid research. Diagnosis to date has been reliant on copromicroscopy or necropsy, which both have significant limitations. The current lack of reliable antemortem diagnostic options is a roadblock to determining the true prevalence and epidemiology of spirorchiidiasis and the development of effective treatment regimes.

Detection of helminths by loop-mediated isothermal amplification assay: a review of updated technology and future outlook

Background

Helminths are endemic in more than half of the world’s countries, raising serious public health concerns. Accurate diagnosis of helminth infection is crucial to control strategies. Traditional parasitological methods, serological tests and PCR-based assays are the major means of the diagnosis of helminth infection, but they are time-consuming and/or expensive, and sometimes provide inaccurate results. Loop mediated isothermal amplification (LAMP) assay, a sensitive, simple and rapid method was therefore developed for detection of helminths. This study aims to discuss the current status of application of LAMP on helminths detection and to make a comprehensive evaluation about this updated technology and its future outlook by comparing with several other diagnostic methods.

Main body

This review summarizes LAMP assay applied for helminth detection and helminthiasis surveillance. The basic principle of LAMP is introduced to help better understand its characteristics and each reported assay is assessed mainly based on its detection sensitivity, specificity and limitations, in comparison with other common diagnostic tests. Moreover, we discuss the limitations of the assays so as to clarify some potential ways of improvement.

Conclusions

Here, we summarize and discuss the advantages, disadvantages and promising future of LAMP in heliminth detection, which is expected to help update current knowledge and future perspectives of LAMP in highly sensitive and specific diagnosis and surveillance of helminthiasis and other parasitic diseases, and can contribute to the elimination of the diseases from endemic areas.

Electronic supplementary material

The online version of this article (10.1186/s40249-019-0530-z) contains supplementary material, which is available to authorized users.

Asian Schistosomiasis: Current Status and Prospects for Control Leading to Elimination

Schistosomiasis is an infectious disease caused by helminth parasites of the genus Schistosoma. Worldwide, an estimated 250 million people are infected with these parasites with the majority of cases occurring in sub-Saharan Africa. Within Asia, three species of Schistosoma cause disease. Schistosoma japonicum is the most prevalent, followed by S. mekongi and S. malayensis. All three species are zoonotic, which causes concern for their control, as successful elimination not only requires management of the human definitive host, but also the animal reservoir hosts. With regard to Asian schistosomiasis, most of the published research has focused on S. japonicum with comparatively little attention paid to S. mekongi and even less focus on S. malayensis. In this review, we examine the three Asian schistosomes and their current status in their endemic countries: Cambodia, Lao People's Democratic Republic, Myanmar, and Thailand (S. mekongi); Malaysia (S. malayensis); and Indonesia, People's Republic of China, and the Philippines (S. japonicum). Prospects for control that could potentially lead to elimination are highlighted as these can inform researchers and disease control managers in other schistosomiasis-endemic areas, particularly in Africa and the Americas.

Distribution of Biomphalaria Snails in Associated Vegetations and Schistosome Infection Prevalence Along the Shores of Lake Victoria in Mbita, Kenya: A Cross-Sectional Study

Background:

Schistosomiasis due to Schistosoma mansoni remains a major public health problem and cause of morbidity and mortality in sub-Saharan Africa despite the implementation of control programmes. More than 6 million Kenyans are at risk of infection. Regarding control measures, Biomphalaria snail species, which are the obligatory intermediate hosts for transmission of S. mansoni, have been neglected. Mbita subcounty in Homa Bay County, western Kenya, along Lake Victoria basin, has a high prevalence of S. mansoni infection despite mass drug administration. This study aimed to determine the abundance of Biomphalaria, with their associated vegetation and schistosome infection rates, along Mbita shoreline.

Methods:

Sixteen purposively selected sites along the Mbita shoreline were sampled for Biomphalaria snails using a 30-minute scooping technique. Global positioning system technology was used to map selected sites. The associated vegetation at sampling sites were collected and identified. Schistosome infection status among the snails was determined via the detection of cercaria shedding.

Results:

A total of 3,135 Biomphalaria sudanica snails were collected. The number of snails collected differed significantly between the 16 sites (F=11.735; degrees of freedom [df]=15.836; P<.001). Significant mean differences (MD) were also observed in terms of the number of snails collected per vegetation type (F=7.899; df=5.846; P<.001). The mean number of snails collected from Cyprus gracilis was significantly higher than that from Enydra fluactuants (MD= 2.03; P<.001), Eichhornia crassipes (MD=4.15; P<.010), and E. fluactuants mixed with E. crassipes (MD=2.516; P<.010). A total of 21 (0.67%) snails shed human cercariae, while 27 (0.86%) snails shed nonhuman cercariae, despite 14 sites having human faeces contamination.

Conclusion:

Although the schistosome infection prevalence among the snails was low, these sites may still be important exposure sites. C. gracilis is the main vegetation type associated with a high abundance of Biomphalaria snails. Molecular techniques are necessary for verification of schistosome positivity among the snails.

DNA Diagnostics for Schistosomiasis Control

Despite extensive efforts over the last few decades, the global disease burden of schistosomiasis still remains unacceptably high. This could partly be attributed to the lack of accurate diagnostic tools for detecting human and animal schistosome infections in endemic areas. In low transmission and low prevalence areas where schistosomiasis elimination is targeted, case detection requires a test that is highly sensitive. Diagnostic tests with low sensitivity will miss individuals with low infection intensity and these will continue to contribute to transmission, thereby interfering with the efficacy of the control measures operating. Of the many diagnostic approaches undertaken to date, the detection of schistosome DNA using DNA amplification techniques including polymerase chain reaction (PCR) provide valuable adjuncts to more conventional microscopic and serological methods, due their accuracy, high sensitivity, and the capacity to detect early pre-patent infections. Furthermore, DNA-based methods represent important screening tools, particularly in those endemic areas with ongoing control where infection prevalence and intensity have been reduced to very low levels. Here we review the role of DNA diagnostics in the path towards the control and elimination of schistosomiasis.

Field and laboratory comparative evaluation of a LAMP assay for the diagnosis of urogenital schistosomiasis in Cubal, Central Angola

OBJECTIVE

To evaluate the performance of Rapid-Heat LAMPellet assay in field conditions for diagnosis of urogenital schistosomiasis in an endemic area in Cubal, Angola, and to assess the reproducibility in a reference laboratory.

METHODS

A total of 172 urine samples from school-age children were tested for microhaematuria, microscopic detection of Schistosoma haematobium eggs and LAMP for DNA detection. Urine samples were stored in a basic equipped laboratory. Field-LAMP tests were performed with and without prior DNA extraction from urine samples, and the results were read by turbidity and by colour change. When field procedures were finished, samples were sent to a reference laboratory to be reanalysed by LAMP.

RESULTS

A total of 83 of 172 (48.3%) were positive for microhaematuria, 87/172 (50.6%) were microscopy-positive for S. haematobium eggs detection, and 127/172 (73.8%) showed LAMP-positive results for detecting S. haematobium using purified DNA and 109/172 (63.4%) without prior DNA extraction. MacNemar's test showed a statistical significant relation between LAMP results and microscopy-detected S. haematobium infections and microhaematuria (P < 0.001 in both cases), respectively. When samples of purified DNA were reanalysed in a reference laboratory in Spain using the same LAMP methodology, the overall reproducibility achieved 72.1%.

CONCLUSIONS

The ease of use, simplicity and feasibility demonstrated by LAMP assay in field conditions together with the acceptable level of reproducibility achieved in a reference laboratory support the use of LAMP assay as an effective test for molecular diagnosis of urogenital schistosomiasis in endemic remote areas.

Development and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Diagnosis of Schistosoma mansoni Infection in Faecal Samples

Human intestinal schistosomiasis is caused by the blood fluke, Schistosoma mansoni. With intensified efforts to control schistosomiasis by mass drug administration using praziquantel (PZQ), there is an urgent need to have accessible, quality-assured diagnostic tests for case detection and disease surveillance and for monitoring efficacy of treatment and other interventions. Current diagnostic tools are limited by suboptimal sensitivity, slow turn-around-time, affordability, and inability to distinguish current from past infections. We describe a simple and rapid diagnostic assay, based on the loop-mediated isothermal amplification (LAMP) technology for diagnosis of S. mansoni infection in human faecal samples. The LAMP primers used in this assay were previously described and they target a 121-bp DNA repeat sequence in S. mansoni. The LAMP assay was optimized at an isothermal temperature of 63°C for 1 hour. The amplified DNA was either visualized under ultraviolet light after electrophoresis or by directly observing the color change after staining the amplicons with CYBR Green dye. The LAMP assay was evaluated against the microscopy-based procedure and the results were analysed using Cohen's kappa coefficient to determine the degree of agreement between the two techniques. The LAMP assay reliably detected S. mansoni ova DNA in faecal samples and parasite DNA in amounts as low as 32fg. When the assay was tested for specificity against other faecal-based soil-transmitted helminths (STH), no cross-reactivity was observed. The LAMP assay was superior to the Kato-Katz assay with a 97% specificity; a high positivity score reliably detecting S. mansoni and a Kappa Coefficient of 0.9 suggested an exceptional agreement between the two techniques. The LAMP assay developed has great potential for application in field settings to support S. mansoni control and elimination campaigns.

Dynamics of spatiotemporal distribution of schistosomiasis in Hubei Province, China

Schistosomiasis caused by parasitic flatworms of blood flukes, remains a major public health concern in China. The significant progress in controlling schistosomiasis in China over the past decades has resulted in the remarkable reduction in the prevalence and intensity of Schistosoma japonicum infection to an extremely low level. Therefore, the elimination of schistosomiasis has been promoted by the Chinese national government. Hubei Province is the major endemic area, that is, along the middle and low reaches of the Yangtze River in the lake and marshland regions of southern China. Eliminating the transmission of schistosomiasis in Hubei Province is challenging. The current issue is to determine the distributions and clusters of schistosomiasis transmission. In this study, we assessed the spatial distribution of schistosomiasis and the risk at the county level in Hubei Province from 2011 to 2015 to provide guidance on the elimination of schistosomiasis transmission in lake and marshland regions. Spatial database of human S.japonicum infection from 2011 to 2015 at the county level in the study area was built based on the annual schistosomias is surveillance data. Moran's I, the global spatial autocorrelation statistics, was utilized to describe the spatial autocorrelation of human S. japonicum infection. In addition, purely spatial scan statistics combined with space-time scan statistics were used to determine the epidemic clusters. Infection rates of S. japonicum decreased in each endemic county in Hubei from 2011 to 2015. Human S. japonicum infection rate showed statistical significance by global autocorrelation analysis during the study period (Moran's I > 0, P < 0.01). This result suggested that there were spatial clusters present in the distribution of S. japonicum infection for the five years. Purely spatial analysis of human S. japonicum infection showed one most likely cluster and one secondary cluster from 2011 to 2015, which covered four and one counties, respectively. Spatiotemporal clustering analysis determined one most likely cluster and one secondary cluster both in 2011-2012, which appeared in 4 and 5 counties, respectively. However, the number of clustering foci decreased with time, and no cluster was detected after 2013.The clustering foci were both located at the Jianghan Plain, along the middle reaches of the Yangtze River and its connecting branch Hanbei River. Spatial distribution of human S. japonicum infections did not change temporally at the county level in Hubei Province. A declining trend in spatiotemporal clustering was observed between 2011 and 2015. However, effective control strategies and integrated prevention should be continuously performed, especially at the Jianghan Plain area along the Yangtze and Hanbei River Basin. Multivariate statistical analysis was carried out to investigate the risk of missing examinations, missing treatment, and unstandardized treatment events. The results showed that age, education level and Sanitary latrines are risk factors for missing examinations (b > 0, OR >1), and treatment times in past and feeding cattle in village group are protective factors (b < 0, OR <1). We also found that age and education level are risk factors for missing treatment (b > 0, OR >1). Study of the risk for un-standardized treatment revealed that occupation is risk factors (b > 0, OR >1), though, education level is protective factors (b < 0, OR <1). Therefore, precise prevention and control should be mainly targeted at these special populations.

Diagnosis of schistosomiasis mansoni: an evaluation of existing methods and research towards single worm pair detection

The inadequacy of current diagnostics for the detection of low worm burdens in humans means that schistosomiasis mansoni is more widespread than previously acknowledged. With the inception of mass drug treatment programmes aimed at disease elimination and the advent of human vaccine trials, the need for more sensitive diagnostics is evident. In this review, we evaluate the merits and limitations of the principal diagnostic methods, namely detection of eggs in faeces; anti-schistosome antibodies in serum; parasite-derived proteins and glycans in serum or urine; parasite DNA in blood, faeces or urine. Only in the baboon model, where actual worm burden is determined by portal perfusion, have faecal smear and circulating antigen methods been calibrated, and shown to have thresholds of detection of 10-19 worm pairs. There is scope for improvement in all the four methods of detection, e.g. the identification of single targets for host antibodies to improve the specificity of enzyme linked immunosorbent assay. Despite recent advances in the definition of the schistosome secretome, there have been no comprehensive biomarker investigations of parasite products in the urine of infected patients. Certainly, the admirable goal of eliminating schistosomiasis will not be achieved unless individuals with low worm burdens can be diagnosed.

Real-time PCR diagnosis of Schistosoma japonicum in low transmission areas of China

Background

Schistosomiasis in the People’s Republic of China (PRC) can be traced back to antiquity. In the past 60 years, the Chinese government has made great efforts to control this persistent disease with elimination slated by 2020 through the implementation of a comprehensive control strategy. This strategy aims to reduce the role of bovines and humans as sources of infection as a pre-requisite for elimination through transmission interruption. The goal of elimination will be achievable only by the implementation of a sustainable surveillance and control system, with sensitive diagnosis a key feature so that the true disease burden is not underestimated. Currently used diagnostics lack the necessary sensitivity to accurately determine the prevalence of Schistosoma japonicum infection in areas with low infection intensities. It is of critical importance to find and treat people and to identify animals with low-level infections if the National Control Programme for China is to achieve schistosomiasis elimination.

Methods

We evaluated a real-time polymerase chain reaction (qPCR) assay using 633 human stool samples collected from five villages in Hunan, Anhui, Hubei, and Jiangxi provinces, and 182 bovine (70 cattle and 112 buffalo) stool samples obtained from four villages in Hunan, Anhui, and Jiangxi provinces in the PRC. All stool samples were subjected to the miracidium hatching test (MHT, a diagnostic procedure used in the National Schistosomiasis Control Programme) and the qPCR assay. Samples positive by MHT were subjected to either the Kato-Katz technique for humans, or the formalin-ethyl acetate sedimentation-digestion (FEA-SD) procedure for bovines, to determine infection intensities.

Results

The qPCR assay exhibited a high level of sensitivity in the detection of S. japonicum infections. With both the human and bovine samples, a significantly higher prevalence was determined using the qPCR assay (11.06% humans, 24.73% bovines) than with the MHT (0.93% humans, 7.69% bovines). The animal contamination index (calculated using data obtained with the qPCR technique) for all positive bovines was 27 618 000 eggs per day, indicating a considerable amount of environmental egg contamination that would be underestimated using less sensitive diagnostic procedures.

Conclusions

The qPCR assay we have evaluated will be applicable as a future field diagnostic and surveillance tool in low-transmission zones where schistosomiasis elimination is targeted and for monitoring post-intervention areas to verify that elimination has been maintained.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0390-y) contains supplementary material, which is available to authorized users.

Nested-PCR assay for detection of Schistosoma japonicum infection in domestic animals

BACKGROUND

Schistosomiasis japonica is a common zoonosis. Domestic animals are the primary source of infection and play an important role in disease transmission. The prevalence and infectivity of this disease in domestic animals in China have significantly decreased and, for this reason, diagnostics with a higher sensitivity have become increasingly necessary. It was reported that polymerase chain reaction (PCR)-based methods could be used to detect schistosome infection in humans and animals and presented a high sensitivity and specificity. The present study aimed to develop a PCR-based method for detection of Schistosoma japonicum infection in domestic animals.

METHODS

A specific nested-PCR assay was developed to detect S. japonicum infection in domestic animals via amplification of a 231-bp DNA fragment of retrotransposon SjR2. The developed assay was first used in sera and dry blood filter paper (DBFP) from goats and buffaloes at different time points of infection. Then, 78 DBFPs from 39 artificially-infected bovines at 14 and 28 days post-infection and 42 DBFPs from schistosome-negative bovines from the city of Huangshan in the Anhui province were used to evaluate the diagnostic validity. Furthermore, this assay was used to detect S. japonicum infection in domestic animals in Dongzhi and Wangjiang counties.

RESULTS

The expected PCR product was detected in eggs and adult worms of S. japonicum and blood samples from S. japonicum-infected goats and water buffaloes, but not from Fasciola and Haemonchus contortus worms. The nested-PCR assay could detect the target S. japonicum DNA in DBFPs from goats and buffaloes after day 3 post-infection. The sensitivity in buffaloes at 14 and 28 days post-infection was 92.30% (36/39) and 100% (39/39), respectively. The specificity was 97.60% (41/42). The positivity rates in Dongzhi and Wangjiang counties were 6.00% and 8.00% in bovines and 22.00% and 16.67% in goats, respectively. The positivity rates in goats in both counties were higher than those in bovines with a significant difference in Dongzhi County but not in Wangjiang County (P < 0.05 and P = 0.23, respectively).

CONCLUSIONS

Our results suggest that the developed nested-PCR assay may be used for the diagnosis of S. japonicum infection in domestic animals, and the control of S. japonicum infection in goats should be paid more attention.

A novel duplex ddPCR assay for the diagnosis of schistosomiasis japonica: proof of concept in an experimental mouse model

The current World Health Organization strategic plan targets the elimination of schistosomiasis as a public health problem by 2025 and accurate diagnostics will play a pivotal role in achieving this goal. DNA-based detection methods provide a viable alternative to some of the commonly used tests, notably microscopy and serology, for the diagnosis of schistosomiasis. The detection of parasite cell-free DNA in different clinical samples is a recent valuable advance, which provides significant benefits for accurate disease diagnosis. Here we validated a novel duplex droplet digital PCR assay for the diagnosis of Chinese (SjC) and Philippine (SjP) strains of Schistosoma japonicum infection in a mouse model. The assay proved applicable for both SjC and SjP infections and capable of detecting infection at a very early intra-mammalian stage in conveniently obtainable samples (urine and saliva) as well as in serum and feces. The target DNA copy numbers obtained in the assay showed a positive correlation with the infection burden assessed by direct traditional parasitology. The potential to detect parasite DNA in urine and saliva has important practical implications for large-scale epidemiological screening programmes in the future, particularly in terms of logistical convenience, and the assay has the potential to be a valuable additional tool for the diagnosis of schistosomiasis japonica.

Field evaluation of a recombinase polymerase amplification assay for the diagnosis of Schistosoma japonicum infection in Hunan province of China

Background

Current diagnostic methods for Schistosoma japonicum infection are insensitive for low-density infections. Therefore, a new diagnostic assay based on recombinase polymerase amplification (RPA) technology was established and assessed for field applification.

Methods

The S.japonicum RPA assay was developed to target highly repetitive retrotransposon SjR2 gene of S japonicum, and its sensitivity and specificity were assessed by serial dilution of S. japonicum genomic DNA and other related worm genomic DNA respectively. The RPA diagnostic validity was first evaluated in 60 fecal samples from healthy people and patients, and then compared with other diagnostic tests in 200 high-risk individuals living in endemic areas.

Results

The real time RPA assay could detect 0.9 fg S. japonicum DNA within 15 min and distinguish S. japonicum from other worms. The validity analysis of RPA for the detection of S. japonicum in stool samples from 30 S. japonicum-infected patients and 30 healthy persons indicated 100% sensitivity and specificity. When testing 200 fecal or serum samples from a high-risk population, the percentage sensitivity of RPA was 100%, whereas that of indirect hemagglutination assay (IHA) and enzyme-linked immunosorbent assay (ELISA) were 80.3% and 85.2% respectively. In addition, the RPA presented better consistency with the stool-based tests than IHA and ELISA. Overall, the RPA was superior to other detection methods with respect to detection time, sensitivity, and convenience.

Conclusions

This is the first time we applied the RPA technology to the field evaluation of S. japonicum infection. And the results suggest that RPA-based assays can be used as a promising point-of-care test for the diagnosis of schistosomiasis.

Use of Molecular Methods for the Rapid Mass Detection of Schistosoma mansoni (Platyhelminthes: Trematoda) in Biomphalaria spp. (Gastropoda: Planorbidae)

The low stringency-polymerase chain reaction (LS-PCR) and loop-mediated isothermal amplification (LAMP) assays were used to detect the presence of S. mansoni DNA in (1) Brazilian intermediate hosts (Biomphalaria glabrata, B. straminea, and B. tenagophila) with patent S. mansoni infections, (2) B. glabrata snails with prepatent S. mansoni infections, (3) various mixtures of infected and noninfected snails; and (4) snails infected with other trematode species. The assays showed high sensitivity and specificity and could detect S. mansoni DNA when one positive snail was included in a pool of 1,000 negative specimens of Biomphalaria. These molecular approaches can provide a low-cost, effective, and rapid method for detecting the presence of S. mansoni in pooled samples of field-collected Biomphalaria. These assays should aid mapping of transmission sites in endemic areas, especially in low prevalence regions and improve schistosomiasis surveillance. It will be a useful tool to monitor low infection rates of snails in areas where control interventions are leading towards the elimination of schistosomiasis.

Diagnostic Tests to Support Late-Stage Control Programs for Schistosomiasis and Soil-Transmitted Helminthiases

Global efforts to address schistosomiasis and soil-transmitted helminthiases (STH) include deworming programs for school-aged children that are made possible by large-scale drug donations. Decisions on these mass drug administration (MDA) programs currently rely on microscopic examination of clinical specimens to determine the presence of parasite eggs. However, microscopy-based methods are not sensitive to the low-intensity infections that characterize populations that have undergone MDA. Thus, there has been increasing recognition within the schistosomiasis and STH communities of the need for improved diagnostic tools to support late-stage control program decisions, such as when to stop or reduce MDA. Failure to adequately address the need for new diagnostics could jeopardize achievement of the 2020 London Declaration goals. In this report, we assess diagnostic needs and landscape potential solutions and determine appropriate strategies to improve diagnostic testing to support control and elimination programs. Based upon literature reviews and previous input from experts in the schistosomiasis and STH communities, we prioritized two diagnostic use cases for further exploration: to inform MDA-stopping decisions and post-MDA surveillance. To this end, PATH has refined target product profiles (TPPs) for schistosomiasis and STH diagnostics that are applicable to these use cases. We evaluated the limitations of current diagnostic methods with regards to these use cases and identified candidate biomarkers and diagnostics with potential application as new tools. Based on this analysis, there is a need to develop antigen-detecting rapid diagnostic tests (RDTs) with simplified, field-deployable sample preparation for schistosomiasis. Additionally, there is a need for diagnostic tests that are more sensitive than the current methods for STH, which may include either a field-deployable molecular test or a simple, low-cost, rapid antigen-detecting test.

Biompha-LAMP: A New Rapid Loop-Mediated Isothermal Amplification Assay for Detecting Schistosoma mansoni in Biomphalaria glabrata Snail Host

Background

Schistosomiasis remains one of the most common endemic parasitic diseases affecting over 230 million people worlwide. Schistosoma mansoni is the main species causing intestinal and hepatic schistosomiasis and the fresh water pulmonate snails of the genus Biomphalaria are best known for their role as intermediate hosts of the parasite. The development of new molecular monitoring assays for large-scale screening of snails from transmission sites to detect the presence of schistosomes is an important point to consider for snail control interventions related to schistosomiasis elimination. Our work was focussed on developing and evaluating a new LAMP assay combined with a simple DNA extraction method to detect S. mansoni in experimentally infected snails as a diagnostic tool for field conditions.

Methodology/Principal findings

A LAMP assay using a set of six primers targeting a sequence of S. mansoni ribosomal intergenic spacer 28S-18S rRNA was designed. The detection limit of the LAMP assay was 0.1 fg of S. mansoni DNA at 63°C for 50 minutes. LAMP was evaluated by examining S. mansoni DNA in B. glabrata snails experimentally exposed to miracidia at different times post-exposure: early prepatent period (before cercarial shedding), light infections (snails exposed to a low number of miracidia) and detection of infected snails in pooled samples (within a group of uninfected snails). DNA for LAMP assays was obtained by using a commercial DNA extraction kit or a simple heat NaOH extraction method. We detected S. mansoni DNA in all groups of snails by using no complicated requirement procedure for DNA obtaining.

Conclusions/Significance

Our LAMP assay, named Biompha-LAMP, is specific, sensitive, rapid and potentially adaptable as a cost-effective method for screening of intermediate hosts infected with S. mansoni in both individual snails and pooled samples. The assay could be suitable for large-scale field surveys for schistosomes control campaigns in endemic areas.

Schistosoma mansoni is the main species causing intestinal and hepatic schistosomiasis worldwide and the snails of the genus Biomphalaria are best known for their role as intermediate hosts of the parasite. Molecular xenomonitoring for large-scale screening of snails from transmission sites to detect the presence of schistosomes is an important point to consider for snail control interventions related to schistosomiasis elimination. In our study, we have developed a new simple rapid LAMP assay to detect S. mansoni in Biomphalaria glabrata snails under different situations of infection: early prepatent period, light or low-grade infections and in snails pooled samples. Besides, a simple and rapid method for DNA extraction from snails' tissues was successfully used. This LAMP assay (named Biompha-LAMP) could be potentially useful for large-scale screening in searching infected snails with S. mansoni in field applicable conditions.

Comparison of molecular and conventional methods for the diagnosis of Fasciola hepatica infection in the field

The liver fluke, Fasciola hepatica, is one of the major parasite threats to livestock industries world-wide. In sheep and cattle, F. hepatica infection is commonly diagnosed using a range of methods. Aside from conventional coprological and serological diagnostic methods, there are also several molecular methods available based on the detection of liver fluke DNA in faeces. In this study, the outcomes of faecal egg count (FEC), serology and coproantigen ELISA (cELISA) were compared with the performance of polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) in diagnosis of F. hepatica from naturally infected cattle and sheep. A total of 64 individual faecal and serum samples were collected from four sheep and beef cattle herds with previous histories of F. hepatica infection. FEC and coproantigen levels were measured in faecal samples and anti-F.hepatica antibody levels were measured in serum samples. DNA samples isolated from faeces were examined both by PCR and LAMP, targeting the internal transcribed spacer 2 (ITS2) region of the F. hepatica genome. Results showed that F. hepatica eggs were present in 28 animals, while coproantigen and specific anti-F. hepatica antibodies were detected in 36 and 53 animals, respectively. Only 3 and 6 samples were positive by PCR and LAMP, respectively. To calculate method specificity and sensitivity, a combination of FEC and cELISA was selected as the composite reference standard (CRS). When compared to the CRS, PCR had a sensitivity of 10.7% and specificity of 100%, whereas LAMP had a sensitivity and specificity of 17.9% and 97.2%, respectively. PCR and LAMP in this field study were highly specific, but both had poor sensitivity compared with FEC and cELISA. Potential reasons for PCR and LAMP failure were inadequate amounts of amplifiable F. hepatica DNA, possibly due to the choice of DNA extraction procedure, amount of faecal material processed, as well as different faeces consistency and composition between different animal species.