Identification of a linear B-cell epitope on the Schistosoma japonicum saposin protein, SjSAP4: Potential as a component of a multi-epitope diagnostic assay.

BACKGROUND: Schistosoma japonicum is one of three major species of blood flukes causing schistosomiasis, a disease, which continues to be a major public health issue in the Philippines. SjSAP4, a member of a multigene family of saposin-like proteins, is a recognized immunodiagnostic biomarker for schistosomiasis japonica. This study aimed to identify linear B-cell epitopes on SjSAP4 and to validate their potential as components of a multi-epitope assay for the serological diagnosis of schistosomiasis japonica. METHODOLOGY: SjSAP4-derived peptides were expressed as GST-peptide-fused proteins and these were Western blot probed with human serum samples from S. japonicum Kato-Katz (KK)-positive individuals and uninfected controls. A core epitope was further identified by Western blotting through probing a series of truncated peptides with the schistosomiasis patient sera. The diagnostic performance of the core epitope-containing peptides and the full-length SjSAP4 was evaluated by enzyme-linked immunosorbent assay (ELISA) using a panel of sera collected from subjects resident in a schistosomiasis-endemic area of the Philippines. MAIN FINDINGS: As a result of the peptide mapping, one peptide (P15) was found to be highly immunogenic in the KK-positive individuals. We subsequently showed that -S163QCSLVGDIFVDKYLD178- is a core B-cell epitope of P15. Subsequent ELISAs incorporating SjSAP4, SjSAP4-Peptide and SjSP-13V2-Peptide showed a sensitivity of 94.0%, 46.0% and 74.0%, respectively, and a specificity of 97.1%, 100% and 100%, respectively. Notably, complementary recognition of the B-cell epitopes (SjSAP4-Peptide and SjSP-13V2-Peptide) was observed in a subset of the KK-positive individuals. A dual epitope-ELISA (SjSAP4-Peptide + SjSP-13V2-Peptide-ELISA) showed a diagnostic sensitivity of 84.0% and a specificity of 100%. CONCLUSIONS/SIGNIFICANCE: In this study, -S163QCSLVGDIFVDKYLD178- was identified as a dominant linear B-cell epitope on SjSAP4. This peptide and the complementary recognition of other B-cell epitopes using sera from different KK-positive individuals can provide the basis of developing a multi-epitope assay for the serological diagnosis of schistosomiasis.

Co-parasitism of intestinal protozoa and Schistosoma japonicum in a rural community in the Philippines.

BACKGROUND: Co-parasitism is a frequent occurrence in impoverished communities in the tropics resulting in a considerable disease burden. While there are extensive reports of intestinal helminthiases, including schistosomiasis japonica, the occurrence and extent of diseases caused by intestinal protozoa (IP) have yet to be investigated in depth in the Philippines. We present a detailed analysis of polyparasitism in a rural community of Northern Samar, focusing on co-infections of IP with Schistosoma japonicum. METHODS: A descriptive cross sectional study was carried out in 2015 across 18 barangays (villages) endemic for S. japonicum in Northern Samar, the Philippines to assess the burden of human schistosomiasis and IP infections. Faecal samples collected from 412 participants from the 18 barangays were included in the final molecular analysis. A multiplex quantitative PCR assay was developed and used for the detection of Blastocystis spp., Entamoeba histolytica, Cryptosporidium spp. and Giardia duodenalis in stool samples. The findings were combined with previous results of droplet digital PCR diagnosis of individuals from the same 18 barangays infected with S. japonicum determined using the same stool samples for analysis. RESULTS: Mean age of the study participants was 40.3 years (95% CI: 38.8-41.8) with 53% (n = 218) being males. Prevalence of S. japonicum (74.5%) and Blastocystis spp. (58.7%) was significantly higher compared to other infections, with E. histolytica having the lowest prevalence (12.1%). A majority of individuals were infected with more than one parasite with two infections being most common (n = 175, 42.5%). The prevalence of individuals with two parasites was significantly higher than all others with 27.9% (n = 115) subjects harbouring a single parasite species. Of individuals with two infections, S. japonicum and Blastocystis spp. were the most common combination (n = 110, 62.9%). Examining age within the population, 58.5% (n = 38) of school-aged children and 60.1% (n = 14) of women of child bearing age harboured at least two parasite species. CONCLUSIONS: The study revealed that polyparasitism with IP infections and schistosomiasis japonica is highly prevalent in individuals in Northern Samar which likely contributes to the significant public health and socio-economic burden suffered by this population. More generally, the findings are of relevance when considering implementation of integrated control strategies for intestinal parasites.

Biennial versus annual treatment for schistosomiasis and its impact on liver morbidity.

OBJECTIVE: This study assessed the impact of annual versus biennial praziquantel treatment regimens on the prevalence, intensity of infection, and liver fibrosis dynamics of Asiatic schistosomiasis (caused by Schistosoma japonicum) among individuals residing in 18 endemic barangays in Northern Samar, Philippines. METHODS: Five hundred and sixty-five subjects who reported symptoms of gastrointestinal illness and/or were believed to have clinical morbidity based on physical examination were selected for cohort follow-up. RESULTS: The mean prevalence of schistosomiasis was 34% and the mean intensity of infection was 123.1 eggs per gram. Moderate to severe hepatic fibrosis (grade II/III) was demonstrated in approximately 25% of the study population. As expected, a greater reduction in both the prevalence and intensity of infection was documented with two treatment rounds versus one. Overall, hepatic fibrosis (grades I-III) regressed in only 24.3% of those who received a single treatment and in only 19.3% of those who received two doses. The prevalence of grade II-III fibrosis at baseline (25.2%) remained unchanged 2 years after treatment. CONCLUSIONS: These findings suggest that in order to reverse moderate to severe liver fibrosis due to schistosomiasis and improve clinical outcomes, a higher clinical dosage of praziquantel (i.e., 60-80mg/kg) may be required over an extended duration.

Diagnosing schistosomiasis-induced liver morbidity: implications for global control.

BACKGROUND: Subclinical morbidity due to schistosomiasis was evaluated in 565 patients, and the enhanced liver fibrosis (ELF) test was assessed for the first time as a potential screening tool for disease. METHODS: The prevalence and intensity of infection were determined by Kato-Katz thick smear stool examination at baseline and 2 years after curative treatment. The degree of hepatic fibrosis was assessed by ultrasound. Non-invasive serum biomarkers of hepatic fibrosis were also evaluated. RESULTS: The baseline human prevalence and infection intensity were found to be moderately high at 34% and 123 eggs per gram, respectively. However, hepatic parenchymal fibrosis occurred in 50% of subjects, with grade II fibrosis in 19% and grade III in 6%. The ELF score and higher serum levels of tissue inhibitor of metalloproteinase 1 (TIMP-1) and hyaluronic acid (HA) correlated with the grade of liver fibrosis. CONCLUSIONS: The findings of this study demonstrated that praziquantel treatment had a short-term impact on both the prevalence and intensity of infection, but less of an impact on established morbidity. Higher TIMP-1 and HA serum levels, and an ELF cut-off score of 8 were found to be correlated with the grade of liver fibrosis; these values may, therefore, assist physicians in identifying individuals at greater risk of disease.

Mass drug administration and the global control of schistosomiasis: successes, limitations and clinical outcomes.

PURPOSE OF REVIEW: Preventive chemotherapy is advocated for the global control and elimination of schistosomiasis. Despite the well known short-term benefits of treating patients for schistosomiasis, the impact of mass drug administration (MDA) campaigns to control the disease in the long term remains unresolved. RECENT FINDINGS: Many studies have advocated the success of MDA programs in order to attract donor funds for elimination efforts but such successes are often short-lived given the drug does not alter the life cycle of the organism or prevent reinfection. Within a matter of months to years after halting treatment, the prevalence, intensity of infection and morbidity of disease return to baseline levels. Other mitigating factors contribute to the failings of MDA campaigns namely: poverty, poor drug coverage, poor drug compliance, and, in the case of Asiatic schistosomiasis, zoonotic transmission. Genetic and innate and acquired immunologic mechanisms complicate the epidemiologic picture of schistosomiasis globally, and may contribute indirectly to MDA shortcomings. The possibility of drug resistance is an ever present concern because of the sole reliance on one drug, praziquantel. SUMMARY: Preventive chemotherapy is advocated for the global control and elimination of schistosomiasis. The short-term benefits of MDA campaigns are well documented but the long-term benefits are questionable.

Access to essential paediatric surgery in the developing world: a case of imperforate anus with rectovaginal and rectocutaneous fistulas left untreated.

Anorectal malformations consist of a wide spectrum of conditions which can affect both sexes and involve the distal anus and rectum as well as the urinary and genital tracts. Patients have the best chance of a good functional outcome if the condition is diagnosed early and efficient anatomic repair is promptly instituted. This report describes a rare case of imperforate anus associated with both rectovaginal and rectocutaneous fistulas in a 6-year-old Filipino girl. The case highlights shortcomings in the healthcare delivery system combined with socio-economic factors that contributed to the delay in both diagnosis and the institution of adequate treatment. Care and preventive measures that can be implemented in low-resource settings to reduce the impact of birth defects are also discussed.

Access to essential paediatric eye surgery in the developing world: a case of congenital cataracts left untreated.

Childhood cataracts are a major cause of treatable blindness. Early recognition, surgical intervention and appropriate follow-up after surgery can result in good visual outcomes. However, several factors may impact on the availability of such services, including lack of an available, affordable and accessible comprehensive eye care centre, financial limitations affecting coverage by the national healthcare provider, and household socioeconomic status. We report a case of congenital cataracts in a 12-year-old male adolescent from Northern Samar, the Philippines, who was left blind since birth. This case highlights the disparities in essential health services in the developing world and the challenges patients face in getting the care they need.

Can mass drug administration lead to the sustainable control of schistosomiasis?

BACKGROUND: In the Philippines, the current national control strategy for schistosomiasis is annual mass drug administration (MDA) with 40 mg/kg of praziquantel in all schistosomiasis-endemic villages with a prevalence ≥10%. METHODS: A cross-sectional survey of schistosomiasis was conducted in 2012 on 18 221 individuals residing in 22 schistosomiasis-endemic villages in the province of Northern Samar. The prevalence of schistosomiasis, intensity of Schistosoma infection, and morbidity of disease were assessed. RESULTS: Despite an active schistosomiasis-control program in Northern Samar for >30 years, which included a MDA campaign in the last 5 years, the mean prevalence of schistosomiasis among 10 435 evaluated subjects was 27.1% (95% confidence interval [CI], 26.3%-28.0%), and the geometric mean intensity of infection among 2832 evaluated subjects was 17.2 eggs per gram of feces (95% CI, 16.4-18.1). Ultrasonography revealed high levels of schistosomiasis-induced morbidity in the schistosomiasis-endemic communities. Left lobe liver enlargement (≥70 mm) was evident in 89.3% of subjects. Twenty-five percent of the study population had grade II/III liver parenchyma fibrosis, and 13.3% had splenomegaly (≥100 mm). CONCLUSIONS: MDA on its own was insufficient to control the prevalence of schistosomiasis, intensity of Schistosoma infection, or morbidity of the disease. Alternative control measures will be needed to complement the existing national MDA program.

The chronic enteropathogenic disease schistosomiasis.

Schistosomiasis is a chronic enteropathogenic disease caused by blood flukes of the genus Schistosoma. The disease afflicts approximately 240 million individuals globally, causing approximately 70 million disability-adjusted life years lost. Chronic infections with morbidity and mortality occur as a result of granuloma formation in the intestine, liver, or in the case of Schistosoma haematobium, the bladder. Various methods are utilized to diagnose and evaluate liver fibrosis due to schistosomiasis. Liver biopsy is still considered the gold standard, but it is invasive. Diagnostic imaging has proven to be an invaluable method in assessing hepatic morbidity in the hospital setting, but has practical limitations in the field. The potential of non-invasive biological markers, serum antibodies, cytokines, and circulating host microRNAs to diagnose hepatic fibrosis is presently undergoing evaluation. This review provides an update on the recent advances made with respect to gastrointestinal disease associated with chronic schistosomiasis.

Utility of Diagnostic Imaging in the Diagnosis and Management of Schistosomiasis.

Diagnosis of schistosomiasis is made by demonstration of the parasite ova in stools, urine,and biopsy specimens from affected organs, or presence of antibodies to the different stages of the parasite or antigens circulating in body fluids by serologic techniques. DNA of schistosomes can now also be detected in serum and stool specimens by molecular technique.However, these tests are unable to determine the severity of target organ pathology and resultant complications. Accurate assessment of schistosome-induced morbidities is now made with the use of imaging techniques like ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). US has made major contributions in the diagnosis of hepatosplenic and urinary form of disease. This imaging method provides real time results, is portable (can be carried to the bed side and the field) and is lower in cost than other imaging techniques. Typical findings in hepatosplenic schistosomiasis by US include: hyperechoic fibrotic bands along the portal vessels (Symmer's fibrosis), reduction in the size of the right lobe, hypertrophy of the left lobe, splenomegaly, and ascites. More advanced ultrasound equipment like the colour Doppler ultrasound can characterize portal vein perfusion, a procedure that is critical for the prediction of disease prognosis and for treatment options for complicated portal hypertension. Although CT and MRI are more expensive, are hospital based, and require highly additional specially-trained personnel, they provide more accurate description of the pathology, not only in hepatosplenic and urinary forms of schistosomiasis, but also in the diagnosis of ectopic forms of the disease,particularly involving thebrain and spinal cord. MRI demonstrates better tissue differentiation and lack of exposure to ionizing radiation compared with CT.

Clinical management of advanced schistosomiasis: a case of portal vein thrombosis-induced splenomegaly requiring surgery.

We report for the first time in the Philippines a case of portal vein thrombosis in a 12 year old Filipino boy with advanced schistosomiasis. The boy was referred to the Research Institute for Tropical Medicine (RITM), Manila, due to a rapidly enlarging spleen post-praziquantel treatment. At RITM, liver function tests were within normal limits but complete blood examinations showed pancytopenia and abnormal coagulation times. Serum markers for hepatitis A, B and C were negative. Abdominal MRI revealed schistosome-induced periportal fibrosis. The main portal vein appeared thrombosed with characteristic cavernous transformation of the right portal vein. Varices were seen in the oesophagus, gastrohepatic ligament, and splenic hilum. The spleen was markedly enlarged, with parenchymal foci representing Gamna-Gandy bodies. The patient underwent splenectomy. Histopathologic findings in the liver showed moderate pipestem fibrosis and schistosome egg granulomas. The patient was discharged from the hospital in excellent clinical condition.

Bilharzia in the Philippines: past, present, and future.

Schistosomiasis japonica has a long history in the Philippines. In 1975, 24 endemic provinces were identified in the northern, central, and southern islands of the Philippines. More than five million people were at risk, with approximately one million infected. In 2003, new foci of infection were found in two provinces in the north and central areas. For the past 30 years, human mass drug administration (MDA), utilizing the drug praziquantel, has been the mainstay of control in the country. Recent studies have shown that the schistosomiasis prevalence ranges from 1% to 50% within different endemic zones. Severe end-organ morbidity is still present in many endemic areas, particularly in remote villages with poor treatment coverage. Moreover, subtle morbidities such as growth retardation, malnutrition, anemia, and poor cognitive function in infected children persist. There is now strong evidence that large mammals (e.g. water buffaloes, cattle) contribute significantly to disease transmission, complicating control efforts. Given the zoonotic nature of schistosomiasis in the Philippines, it is evident that the incidence, prevalence, and morbidity of the disease will not be controlled by MDA alone. There is a need for innovative cost-effective strategies to control schistosomiasis in the long term.

Bilharzia: Pathology, Diagnosis, Management and Control.

More than one billion people travel internationally each year and approximately 100 million to the tropics. Schistosomiasis is a neglected tropical disease caused by trematode blood flukes of the genus Schistosoma. It currently infects over 250 million people worldwide and results in approximately 25 million disability adjusted life years lost. Clinical manifestations depend on the affected organ. Subtle morbidities have also been documented including: growth retardation, anaemia and poor cognitive function in children. While schistosomiasis has been eradicated from Japan and significantly reduced in parts of China and Egypt, transmission in many other regions remains ongoing due to the wide-spread distribution of the intermediate snail host, poor sanitation, lack of health education and decreasing compliance to mass drug administration. Integrated control has significantly reduced the burden of disease in China but considerable financial capital is needed if similar results are to be duplicated elsewhere. Human vaccination is in various stages of development, and once found, will become an integral part of future control. This comprehensive review examines the epidemiology, pathology, diagnosis, clinical management, prevention and control of the disease.