The impact of Schistosoma japonicum infection and treatment on ultrasound-detectable morbidity: a five-year cohort study in Southwest China

Schistosomiasis

Schistosomiasis is a major cause of morbidity in the world and almost 800 million people worldwide are at risk for schistosomiasis; it is second only to malaria as a major infectious disease. Globally, it is estimated that the disease affects more than 250 million people in 78 countries of the world and is responsible for some 280,000-500,000 deaths each year. The three major schistosomes infecting humans are Schistosoma mansoni, S. japonicum, and S. haematobium. This chapter covers a wide range of aspects of schistosomiasis, including basic biology of the parasites, epidemiology, immunopathology, treatment, control, vaccines, and genomics/proteomics. In this chapter, the reader will understand the significant toll this disease takes in terms of mortality and morbidity. A description of the various life stages of schistosomes is presented, which will be informative for both those unfamiliar with the disease and experienced scientists. Clinical and public health aspects are addressed that cover acute and chronic disease, diagnosis, current treatment regimens and alternative drugs, and schistosomiasis control programs. A brief overview of genomics and proteomics is included that details recent advances in the field that will help scientists investigate the molecular biology of schistosomes. The reader will take away an appreciation for general aspects of schistosomiasis and the current research advances.

A 14-year follow-up of ultrasound-detected urinary tract pathology associated with urogenital schistosomiasis in women living in the Msambweni region of coastal Kenya

BACKGROUND

Complications of urogenital schistosomiasis include acute inflammatory and chronic fibrotic changes within the urogenital tract. Disease burden of this neglected tropical disease is often underestimated, as only active, urine egg-patent Schistosoma infection is formally considered. Previous studies have focussed on short-term effects of praziquantel treatment on urinary tract pathology, demonstrating that acute inflammation is reversible. However, the reversibility of chronic changes is less well studied.

METHODS

Our study compared, at two time points 14 y apart, urine egg-patent infection and urinary tract pathology in a cohort of women living in a highly endemic area having intermittent praziquantel treatment(s). In 2014 we matched 93 women to their findings in a previous study in 2000.

RESULTS

Between 2000 and 2014 the rate of egg-patent infection decreased from 34% (95% confidence interval [CI] 25 to 44) to 9% (95% CI 3 to 14). However, urinary tract pathology increased from 15% (95% CI 8 to 22) to 19% (95% CI 11 to 27), with the greatest increase seen in bladder thickening and shape abnormality.

CONCLUSIONS

Despite praziquantel treatment, fibrosis from chronic schistosomiasis outlasts the presence of active infection, continuing to cause lasting morbidity. We suggest that future efforts to eliminate persistent morbidity attributable to schistosomiasis should include intensified disease management.

Circulating microRNAs as Biomarkers of Hepatic Fibrosis in Schistosomiasis Japonica Patients in the Philippines

Host-derived microRNAs (miRNAs) play important regulatory roles in schistosomiasis-induced hepatic fibrosis. This study analyzed selected serum miRNAs among Filipino schistosomiasis japonica patients with ultrasound (US)-detectable hepatic fibrosis. A prospective cohort study design with convenience sampling was employed from 2017 to 2019. The study sites were eight endemic barangays in Leyte, Philippines. Eligible chronic schistosomiasis patients with varying severities of hepatic fibrosis were enrolled in the cohort and serially examined at 6, 12, and 24 months from baseline. Baseline serum miR-146a-5p, let-7a-5p, miR-150-5p, miR-122-5p, miR-93-5p, and miR200b-3p were measured using RT-qPCR. A total of 136 chronic schistosomiasis patients were included in this prospective cohort study. Approximately, 42.6% had no fibrosis, 22.8% had mild fibrosis, and 34.6% had severe fibrosis at baseline The serum levels of the antifibrotic miR-146a (p < 0.0001), miR-150 (p = 0.0058), and let-7a (p < 0.0001) were significantly lower in patients with hepatic fibrosis while the profibrotic miR-93 (p = 0.0024) was elevated. miR-146a-5p (AUC = 0.90, 95% CI [0.84, 0.96], p < 0.0001) has the most promising potential to differentiate patients with (n = 78) versus without (n = 58) hepatic fibrosis. The baseline level of serum miR-146-5p was significantly different in patients with progressive fibrosis (n = 17) compared to those who never developed fibrosis (n = 30, p < 0.01) or those who had fibrosis reversal (n = 20, p < 0.01) after 24 months. These findings demonstrate the potential utility of serum miRNAs, particularly of miR-146a, as a supplementary tool for assessing hepatic fibrosis in chronic schistosomiasis japonica patients.

Diagnostic Performance of Parasitological, Immunological, Molecular, and Ultrasonographic Tests in Diagnosing Intestinal Schistosomiasis in Fieldworkers From Endemic Municipalities in the Philippines

Schistosomiasis remains to ha/ve a significant public health impact in the Philippines. The Kato-Katz (K-K) technique is the reference standard and most used technique for definitive diagnosis of intestinal schistosomiasis for control programs in endemic regions. However, this has a very low sensitivity when applied in areas of low endemicity and patients with light infection. Hence, this study determined the diagnostic performance of immunological, molecular, parasitological, and ultrasonographic tests in diagnosing intestinal schistosomiasis in endemic municipalities in the Philippines. We performed a community-based cross-sectional study to determine the positivity of schistosomiasis in Leyte, Philippines. The diagnostic performance of five different detection techniques: (1) three stool K-K with duplicate smears; (2) soluble egg antigen IgG ELISA; (3) urine point-of-care circulating cathodic antigen (POC-CCA) test; (4) detection of Schistosoma japonicum circulating DNA (SjcDNA) in serum and urine samples; (5) focused abdominal ultrasound (US), were also obtained in this study. Multiple stool examinations enhanced the sensitivity of K-K from 26.2% (95% CI [16.4, 38.8]) with single stool to 53.8% (95% CI [41.1, 66.1]) and 69.2% (95% CI [56.4, 80.0]) with two and three stools from consecutive days, respectively. Among the SjcDNA nucleic acid amplification test (NAAT)-based detection assays, loop-mediated isothermal amplification (LAMP) PCR using sera had the highest sensitivity at 92.3% (95% CI [82.2, 97.1]) with LAMP consistently identifying more positive cases in both serum and urine samples. This study showed that single stool K-K, which remains the only diagnostic test available in most endemic areas in the Philippines, had low sensitivity and failed to identify most patients with light infection. SjcDNA detection assay and POC-CCA urine test were more sensitive than stool microscopy in detecting schistosomiasis. On the other hand, US was less sensitive than the widely utilized K-K technique in diagnosing schistosomiasis. This study emphasizes the need to revisit the use of single stool K-K in the surveillance and case detection of schistosomiasis in endemic areas of the Philippines. The availability of advanced and more sensitive diagnostic tests will help better control, prevent, and eliminate schistosomiasis in the country.

Schistosomiasis

Schistosomiasis is a major cause of morbidity in the world; it is second only to malaria as a major infectious disease. Globally, it is estimated that the disease affects over 250 million people in 78 countries of the world and is responsible for some 280,000 deaths each year. The three major schistosomes infecting humans are Schistosoma mansoni, S. japonicum, and S. haematobium. This chapter covers a wide range of aspects of schistosomiasis, including basic biology of the parasites, epidemiology, immunopathology, treatment, control, vaccines, and genomics/proteomics. In this chapter, the reader will understand the significant toll this disease takes in terms of mortality and morbidity. A description of the various life stages of schistosomes is presented, which will be informative for both those unfamiliar with the disease and experienced scientists. Clinical and public health aspects are addressed that cover acute and chronic disease, diagnosis, current treatment regimens and alternative drugs, and schistosomiasis control programs. A brief overview of genomics and proteomics is included that details recent advances in the field that will help scientists investigate the molecular biology of schistosomes. The reader will take away an appreciation for general aspects of schistosomiasis and research advances.

Comparative analysis of codon usage pattern and its influencing factors in Schistosoma japonicum and Ascaris suum

Schistosoma japonicum and Ascaris suum are considered as the major parasites of human which cause various life threatening diseases such as schistomiasis and ascariasis. The codon usage bias (CUB) is known as the phenomenon of more usage of a specific codon than the other synonymous codons for an amino acid. The factors that influence the codon usage bias are mutation pressure, natural selection, gene expression, gene length, GC content, RNA stability, recombination rates, codon position etc. Here we had used various bioinformatic tools and statistical analyses to understand the compositional features, expression level and codon usage bias in the genes of these two species.After estimating the effective number of codon (ENC) in both the species, codon usage bias was found to be low and gene expression was high. The nucleobase A and T were used most often than C and G. From neutrality plot and correspondence analysis it was found that both natural selection and mutation pressure played an important role in shaping the codon usage pattern of both species. Moreover, natural selection played a major role while mutation pressure played a minor role in shaping the codon usage bias in S. japonicum and A.suum. This is the first report on the codon usage biology in S. japonicum and A.suum, and the factors influencing their codon usage bias. These results are expected to be useful for genetic engineering and evolutionary studies.

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

Background

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

Methodology/Principal findings

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

Conclusion/Significance

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

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

Exploring the impact of infection-induced immunity on the transmission of Schistosoma japonicum in hilly and mountainous environments in China

Schistosomiasis has long been a threat to villagers in hilly and mountainous areas of southwestern China where the intermediate snail host is abundant. In recent years our group has focused on the development and parameterization of a community-level mathematical model of S. japonicum transmission that accounts for the role of environmental determinants of transmission intensity in Sichuan Province. To date the model has not incorporated acquired immunity. A review of previous epidemiologic data from our study area in Sichuan suggested modeling of acquired immunity as a function of history of infection. To explore the potential impacts on the dynamics of transmission, a mathematical representation of acquired immunity was incorporated, and parameterized based on this epidemiological evidence. It is shown through simulation that the effect of immunity is to reduce the rate of worm development and thereby lower the endemic level significantly. The effect was more striking at increasing levels of a village'tm)s basic reproductive number. Further, residual immunity modestly alters the threshold of external parasite input necessary to trigger re-emergence of transmission and its subsequent rate of development. Despite limitations in our quantitative knowledge of the immunity function, these findings, along with the uncertainties in transmission dynamics at low infection levels, underscore the need for improved diagnostic methods for disease control, especially in potentially re-emergent settings.

The use of imaging to detect schistosomes and diagnose schistosomiasis

Several imaging modalities have been employed to examine schistosomes and monitor schistosome-induced pathology. Ultrasound is a noninvasive imaging method that has long been used in the laboratory and in the field to evaluate pathological changes, notably fibrosis, that arise as a consequence of the host response to schistosome eggs lodging in a variety of tissues. Ultrasonography has been widely used to monitor changes in the extent of fibrosis and in spleen/liver enlargement following chemotherapeutic treatment for schistosomiasis. Imaging methods to monitor schistosomes themselves in vivo (as opposed to detecting schistosome-induced pathology) include positron emission tomography and fluorescence molecular tomography. Both approaches rely on schistosome uptake of tracers that are introduced into infected animals and that can be detected externally. These methods have been used to successfully detect schistosomes in vivo and to monitor their elimination following chemotherapeutic treatment. Direct monitoring of live schistosomes in vivo has been achieved using intravital microscopy, when the infected tissues of anaesthetized animals are exposed. Finally, schistosome eggs have been visualized by confocal laser scanning microscopy in infected mice as well as in a human patient with schistosomiasis hematobium. Further advances in imaging technologies seem likely to provide greater insight into disease progression and into the biology of schistosomes in the most relevant setting-within a live animal.

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.

Field evaluation of a PCR test for Schistosoma japonicum egg detection in low-prevalence regions of China

Sensitive Schistosoma japonicum detection methods are needed to progress from schistosomiasis control to elimination. The sensitivity of the Kato-Katz thick smear and miracidium hatching tests decrease with infection intensity and serological tests cannot always identify current infections. We evaluated a fecal polymerase chain reaction (PCR) assay to detect S. japonicum infection in 106 humans and 8 bovines in China. PCR was highly sensitive, detecting S. japonicum DNA at 0.5 eggs/g of stool. Comparing PCR examination of a single stool sample to the miracidium hatching test using three consecutive stool samples, more humans were hatching test positive (20%) than PCR positive (15%). However, two individuals were PCR positive in a village where no infections were detected by coprological methods. The sensitivity of PCR makes it a promising tool for schistosomiasis diagnostics and screening, although egg shedding variability and stool sample size present challenges for any detection method in low-transmission areas.