Morbidity associated with schistosomiasis before and after treatment in young children in Rusinga Island, western Kenya

Paediatric schistosomiasis: last mile preparations for deploying paediatric praziquantel

Schistosomiasis is the second most important parasitic disease of public health importance in Africa, affecting over 50 million children aged <5 years old. Schistosomiasis control has focused on treating school-aged children (>6 years) and adults through mass drug administration (MDA). Following the recent development of a paediatric praziquantel (PZQ) formulation for children aged <5 years, there are now concerted efforts to determine optimal and effective ways to integrate treatment of these children into national schistosomiasis control programmes. In this opinion article we outline the pathway for successful drug access, delivery, and mainstreaming of the new formulation in endemic country health systems. Effective and sustained paediatric schistosomiasis treatment is an important target of the 2030 World Health Organization (WHO) neglected tropical diseases (NTDs) roadmap.

Baseline Liver Ultrasound Findings in Preschool Children From the Praziquantel in Preschoolers Trial in Lake Albert, Uganda

BACKGROUND

Periportal fibrosis is a late-stage manifestation of chronic infection with Schistosoma mansoni . Praziquantel (PZQ), the only drug available for the treatment of schistosomiasis, has limited effect in treating established morbidity. Preschool-age children (PSAC) are not considered to be an at-risk population for severe morbidity. However, the prevalence of periportal fibrosis in PSAC in S. mansoni endemic settings is unknown.

METHODS

As part of a phase II clinical trial comparing different dosing regimens of PZQ in children age 12-47 months infected with S. mansoni in Uganda ("praziquantel in preschoolers" trial), we present baseline results assessing liver ultrasound (US) findings as per the WHO Niamey Protocol.

RESULTS

A total of 7/347 (2%) PSAC had Image Pattern C with pipe stems and echogenic rings suggestive of periportal fibrosis, 29/347 (8%) had Image Pattern B and 58 (17%) had evidence of periportal thickening There were higher adjusted odds of periportal thickening with older age [odds ratio (OR): 1.04; 95% confidence interval (CI): 1.00-1.07], primary maternal education (OR: 1.04; 95% CI: 1.00-1.07) and being taken to the lake weekly (OR: 3.02; 95% CI: 1.19-7.63). A further 44/347 children (13%) had a rounded caudal liver edge which was associated with high S. mansoni infection intensity (adjusted OR: 3.31; 95% CI: 1.46-7.51).

CONCLUSIONS

Incipient schistosomiasis-related liver morbidity was detected in young children enrolled in the praziquantel in preschoolers trial. Adequate age-adjusted reference measurements for liver ultrasound findings in very small children are lacking but urgently needed. Schistosomiasis-related fibrosis may be delayed or averted with early and repeated PZQ treatment.

Epidemiology of pediatric schistosomiasis in hard-to-reach areas and populations: a scoping review

BACKGROUND

Schistosomiasis affects over 250 million people worldwide. Despite children and the poor being key risk groups, limited research and control activities target pre-school aged children (PSAC) and hard-to-reach populations. As endemic countries shift the goals of their schistosomiasis programs from morbidity control to disease elimination, there is a need for inclusive planning to cover all affected age groups from all geographical areas and populations to achieve sustainable impact and health equity.

METHODS

We conducted searches in MEDLINE, Web of Science, Embase (Ovid), and LILACS per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Extension for Scoping Reviews (PRISMA-ScR) guidelines. Quality assessment of identified articles was done using the Joanna Briggs Institute Prevalence Critical Appraisal Tool. Relevant study data were extracted from the articles and entered into Microsoft Excel 2016 for descriptive analysis.

RESULTS

From the 17,179 screened articles, we identified 13 eligible studies on schistosomiasis in PSAC living in hard-to-reach areas and populations. All identified studies were from sub-Saharan Africa. The mean sample size of the retained studies was 572, with a balanced sex distribution among the young children sampled in each study. Ten studies investigated Schistosoma mansoni, one investigated Schistosoma haematobium, while two covered both S. mansoni and S. haematobium in the target population. The prevalence of S. mansoni among PSAC in the included studies was estimated at 12.9% in Ghana, 80.3-90.5% in Kenya, 35.0% in Madagascar, 9.6-78.0% in Senegal, 11.2-35.4% in Sierra Leone, 44.4-54.9% in Tanzania and 39.3-74.9% in Uganda. Out of the three studies that investigated S. haematobium, the presence of the infection was reported in only one study carried out in Nigeria. Schistosome infections reported in nearly all studies included in this review were of light intensity. Only one study conducted in Nigeria documented visible hematuria in 17.7% of the PSAC studied.

CONCLUSIONS

The findings document the high prevalence of schistosomiasis among PSAC in hard-to-reach populations and underscore the need to consider this population subgroup when designing the expansion of preventive chemotherapy and schistosomiasis control activities.

The trend of schistosomiasis related bladder cancer in the lake zone, Tanzania: a retrospective review over 10 years period

INTRODUCTION

Bladder cancer is a possible outcome of chronic urinary schistosomiasis in many endemic countries. In Tanzania, the Lake Victoria area is one of the areas with the highest prevalence of urinary schistosomiasis and higher incidences of squamous cell carcinoma (SCC) of the urinary bladder. A previous study in the area over one decade (2001-2010) showed SCC to be common in patients aged below 50 years. With various prevention and intervention programs there are likely to be notable changes in schistosomiasis-related urinary bladder cancer, which is currently unknown. Updated information on the status of SCC in this area will be useful for giving an insights into efficacy of control interventions implemented and help guide the initiation of new ones. Therefore, this study was done to determine the current trend of schistosomiasis-related bladder cancer in lake zone, Tanzania.

METHODS

This was a descriptive retrospective study of histologically confirmed urinary bladder cancer cases diagnosed at the Pathology Department of Bugando Medical Centre over 10 years period. The patient files and histopathology reports were retrieved and information was extracted. Data were analyzed using Chi-square and student t-test.

RESULTS

A total of 481 patients were diagnosed with urinary bladder cancer during the study period whereby, 52.6% were males and 47.4% were females. The mean age regardless of histological type of cancer was 55 ± 14.2 years. The SCC was the commonest histological type accounting for 57.0%, followed by transitional cell carcinoma 37.6%, and 5.4% were adenocarcinomas. The Schistosoma haematobium eggs were observed in 25.2% and were commonly associated with SCC (p = 0.001). Poorly differentiated cancers were observed mostly in females (58.6%) compared to males (41.4%) (p = 0.003). Muscular invasion of the urinary bladder by cancer was observed in 11.4% of the patients, and this was significantly higher in non-squamous than in squamous cancers (p = 0.034).

CONCLUSION

Schistosomiasis-related cancers of the urinary bladder in the Lake zone of Tanzania is still a problem. Schistosoma haematobium eggs were associated with SCC type indicating the persistence of infection in the area. This calls for more efforts on preventive and intervention programs to reduce the burden of urinary bladder cancer in the lake zone.

Absence of lower genital tract lesions among women of reproductive age infected with Schistosoma mansoni: A cross-sectional study using a colposcope in Western Kenya

BACKGROUND

Female genital schistosomiasis (FGS) constitutes four different lesions known to be caused by Schistosoma haematobium ova deposited in the genital tract. Schistosoma mansoni ova may also be found in the genital tract. However, it is not known if S. mansoni causes lower genital tract lesions characteristic of FGS.

METHODOLOGY

This study was conducted in 8 villages along the shores of Lake Victoria, western Kenya. Stool and urine samples, collected from women of reproductive age on three consecutive days, were analysed for S. mansoni and S. haematobium infection. S. mansoni positive and S. haematobium negative willing participants, aged 18-50 years were invited to answer a questionnaire (demographics, symptoms), undergo a gynaecological examination and cytology specimen collection by an FGS expert.

PRINCIPAL FINDINGS

Gynaecologic investigations were conducted in 147 S. mansoni-positive women who had a mean infection intensity of 253.3 epg (95% CI: 194.8-311.9 epg). Nearly 90% of them used Lake Victoria as their main water source. None were found to have cervicovaginal grainy sandy patches or rubbery papules. Homogenous yellow patches were found in 12/147 (8.2%) women. Women with homogenous yellow patches were significantly older (47 years) than the rest (34 years, p = 0.001). No association was found between intensity of S. mansoni infection and homogenous yellow patches (p = 0.70) or abnormal blood vessels (p = 0.14). S. mansoni infection intensity was not associated with genital itch, bloody or malodorous vaginal discharge.

CONCLUSION

S. mansoni infection was neither associated with lower genital tract lesions nor symptoms typically found in women with FGS.

Morbidity associated with Schistosoma mansoni infection in north-eastern Democratic Republic of the Congo

BACKGROUND

Reducing morbidity is the main target of schistosomiasis control efforts, yet only rarely do control programmes assess morbidity linked to Schistosoma sp. infection. In the Democratic Republic of Congo (DRC), and particularly in north-eastern Ituri Province, little is known about morbidity associated with Schistosoma mansoni infection. For this reason, we aimed to assess intestinal and hepatosplenic morbidity associated with S. mansoni infection in Ituri Province.

METHODS/PRINCIPAL FINDINGS

In 2017, we conducted a cross-sectional study in 13 villages in Ituri Province, DRC. S. mansoni infection was assessed with a Kato-Katz stool test (2 smears) and a point-of-care circulating cathodic antigen (POC-CCA) urine test. A questionnaire was used to obtain demographic data and information about experienced intestinal morbidity. Each participant underwent an abdominal ultrasonography examination to diagnose hepatosplenic morbidity. Of the 586 study participants, 76.6% tested positive for S. mansoni. Intestinal morbidity reported in the two preceding weeks was very frequent, and included abdominal pain (52.7%), diarrhoea (23.4%) and blood in the stool (21.5%). Hepatosplenic morbidity consisted of abnormal liver parenchyma patterns (42.8%), hepatomegaly (26.5%) and splenomegaly (25.3%). Liver pathology (adjusted odds ratio [aOR] 1.20, 95% confidence interval [CI] 1.06-1.37, p = 0.005) was positively and significantly associated with S. mansoni infection. Hepatomegaly (aOR 1.52, 95% CI 0.99-2.32, p = 0.053) and splenomegaly (aOR 1.12, 95% CI 0.73-1.72, p = 0.619) were positively but not significantly associated with S. mansoni infection at the individual level. At the village level, S. mansoni prevalence was positively associated with the prevalence of hepatomegaly and splenomegaly. High-intensity S. mansoni infections were associated with diarrhoea, blood in the stool, hepatomegaly, splenomegaly, and liver parenchyma (C, D, E and F pathology patterns). Four study participants were diagnosed with ascites and five reported hematemesis.

CONCLUSIONS/SIGNIFICANCE

Our study documents a high burden of intestinal and hepatosplenic morbidity associated with S. mansoni infection status in Ituri Province. The findings call for targeted interventions to address both S. mansoni infection and related morbidity.

Regression of Schistosoma mansoni associated morbidity among Ugandan preschool children following praziquantel treatment: A randomised trial

Preschool children suffer from morbidity attributable to Schistosoma mansoni. We compared a single and double dose of praziquantel treatment on the regression of S. mansoni associated morbidity in children less than six years in Uganda. We measured the sizes of spleen and liver as well as liver fibrosis before treatment and 8 months after treatment among children who either received one dose (n = 201) or two doses (n = 184) of praziquantel (standard oral dose of 40 mg/kg body weight). Heamoglobin measurements were also taken. Overall, liver enlargement reduced from 52.2% (95% CI (Confidence interval) 45.1, 59.3) to 17.9% (95% CI 12.9, 23.9) with a single dose and from 48.4 (95% CI 40.9, 55.8) to 17.9% (95% CI 12.7, 24.3) with a double dose and there was no significant difference between the changes in proportion of children with enlarged liver between the two treatment groups. The proportion of children with enlarged spleen was not significantly reduced in the group treated with either one or two doses, 47.8% (95% CI 41.7, 54.9) to 45.3% (95% CI 38.3, 52.4) and 48.4% (95% CI 40.9,55.8) to 40.8% 95% CI 33.6, 48.2), respectively. Liver fibrosis detected among children getting single dose (n = 9) or double doses (n = 13) resolved after treatment with praziquantel. The number of children with low heamoglobin significantly reduced from 51.2% (95% CI 44.1, 58.3) to 0.5% (0.2, 0.8) and 61.4% (95% CI 53.9,68.5) to 1.1% (95% CI 0.1, 3.9) after single and double dose treatment, respectively. These results suggest that there is no evidence of a difference in effect between one dose of praziquantel and two doses in reversing morbidity attributable to S. mansoni among children less than six years of age.

Associations between infection intensity categories and morbidity prevalence in school-age children are much stronger for Schistosoma haematobium than for S. mansoni

BACKGROUND

World Health Organization (WHO) guidelines for measuring global progress in schistosomiasis control classify individuals with Schistosoma spp. infections based on the concentration of excreted eggs. We assessed the associations between WHO infection intensity categories and morbidity prevalence for selected S. haematobium and S. mansoni morbidities in school-age children.

METHODOLOGY

A total of 22,488 children aged 6-15 years from monitoring and evaluation cohorts in Burkina Faso, Mali, Niger, Uganda, Tanzania, and Zambia from 2003-2008 were analyzed using Bayesian logistic regression. Models were utilized to evaluate associations between intensity categories and the prevalence of any urinary bladder lesion, any upper urinary tract lesion, microhematuria, and pain while urinating (for S. haematobium) and irregular hepatic ultrasound image pattern (C-F), enlarged portal vein, laboratory-confirmed diarrhea, and self-reported diarrhea (for S. mansoni) across participants with infection and morbidity data.

PRINCIPAL FINDINGS

S. haematobium infection intensity categories possessed consistent morbidity prevalence across surveys for multiple morbidities and participants with light infections had elevated morbidity levels, compared to negative participants. Conversely, S. mansoni infection intensity categories lacked association with prevalence of the morbidity measures assessed.

CONCLUSIONS/SIGNIFICANCE

Current status infection intensity categories for S. haematobium were associated with morbidity levels in school-age children, suggesting urogenital schistosomiasis morbidity can be predicted by an individual's intensity category. Conversely, S. mansoni infection intensity categories were not consistently indicative of childhood morbidity at baseline or during the first two years of a preventive chemotherapy control program.

Concomitant Immunity and Worm Senescence May Drive Schistosomiasis Epidemiological Patterns: An Eco-Evolutionary Perspective

In areas where human schistosomiasis is endemic, infection prevalence and egg output are known to rise rapidly through childhood, reach a peak at 8-15 years of age, and decline thereafter. A similar peak ("overshoot") followed by return to equilibrium infection levels sometimes occurs a year or less after mass drug administration. These patterns are usually assumed to be due to acquired immunity, which is induced by exposure, directed by the host's immune system, and develops slowly over the lifetime of the host. Other explanations that have been advanced previously include differential exposure of hosts, differential mortality of hosts, and progressive pathology. Here we review these explanations and offer a novel (but not mutually exclusive) explanation, namely that adult worms protect the host against larval stages for their own benefit ("concomitant immunity") and that worm fecundity declines with worm age ("reproductive senescence"). This explanation approaches schistosomiasis from an eco-evolutionary perspective, as concomitant immunity maximizes the fitness of adult worms by reducing intraspecific competition within the host. If correct, our hypothesis could have profound implications for treatment and control of human schistosomiasis. Specifically, if immunity is worm-directed, then treatment of long-standing infections comprised of old senescent worms could enable infection with new, highly fecund worms. Furthermore, our hypothesis suggests revisiting research on therapeutics that mimic the concomitant immunity-modulating activity of adult worms, while minimizing pathological consequences of their eggs. We emphasize the value of an eco-evolutionary perspective on host-parasite interactions.

Is there a gap between health education content and practice toward schistosomiasis prevention among schoolchildren along the shores of Lake Victoria in Kenya?

Despite provision of preventive measures against schistosomiasis such as mass drug administration (MDA), the prevalence of Schistosoma mansoni remains high in communities living near Lake Victoria. This study aimed to analyse the status of schistosomiasis, including its prevalence, health education, knowledge, attitudes, and practices (KAP) among pupils, and water use in schools in Mbita situated along the shores of Lake Victoria. Four primary schools were selected as target schools and pupils in classes six and seven were recruited as study participants. The prevalence of S. mansoni was examined by Kato-Katz method. Simultaneously, a KAP survey toward schistosomiasis was conducted among the pupils. Health education contents were extracted from textbooks. All primary schools in the study site were surveyed regarding how each secured water used for daily school life. The prevalence of S. mansoni was 56% and 36% in 2015 and 2016, respectively. 60–70% of pupils chose a correct answer for the mode of transmission. More than 70% of pupils answered that bathing in Lake Victoria causes Schistosoma infection; however, more than 70% of pupils bathed in Lake Victoria sometimes or every day. According to the science textbook, “avoiding contact with contaminated water” is the way to prevent schistosomiasis; however, 66% of schools asked pupils to bring water from Lake Victoria. The prevalence of S. mansoni among pupils remains high. Schoolchildren are taught to avoid contact with contaminated water but are often asked to fetch water from the lake. From the school health viewpoint, health education that reflects the social and cultural context of the community in the contents and teaching methods are needed. In addition to this, provision of sanitation infrastructure is needed. A comprehensive and innovative approach which harmonises central and local governments and other stakeholders, as well as community is important to prevent schistosomiasis.

According to WHO, it is estimated that at least 206 million people required preventive treatment for schistosomiasis in 2016 and of those at least 90% live in Africa. Moreover, school-age children are most affected by this worm. In Kenya, despite preventive measures against schistosomiasis such as mass drug administration (MDA) in primary schools, it remains a major public health problem, especially along the shores of Lake Victoria. Our study revealed that the prevalence of Schistosoma mansoni was high among pupils despite their knowledge about schistosomiasis transmission. This can be attributed to lack of safe water supply and latrines. A comprehensive approach which harmonises central and local governments and other stakeholders, as well as community is needed to prevent schistosomiasis. For example, the combination of health education (in which schools play as focal point) with provision of water infrastructure, encouragement to use and construct toilets in both schools and community/households, snail control, and MDA with monitoring can be employed to control and prevent schistosomiasis. From the school health viewpoint, it is necessary to develop health education contents and teaching methods that reflect the social and cultural context of the community in order to improve their behaviour and change the social norm.

The prevalence of schistosomiasis in Uganda: A nationally representative population estimate to inform control programs and water and sanitation interventions

Background

To improve schistosomiasis control programs in Uganda, where intestinal schistosomiasis is a widespread public health problem, a country-wide assessment of the disease prevalence among all age ranges is needed. Few studies have aimed to quantify the relationships between disease prevalence and water and sanitation characteristics across Uganda to understand the potential to interrupt disease transmission with an integrated package of interventions.

Methodology/Principal findings

A nationally representative survey was undertaken that included a household and individual questionnaire followed by disease testing based on detection of worm antigens (circulating cathodic antigen–CCA), diagnosis and treatment. A comprehensive set of questions was asked of randomly sampled individuals, two years of age and above, to understand their water and sanitation infrastructure, open defecation behaviors, exposure to surface water bodies, and knowledge of schistosomiasis. From a set of 170 randomly sampled, geographically diverse enumeration areas, a total of 9,183 study participants were included. After adjustment with sample weights, the national prevalence of schistosomiasis was 25.6% (95% confidence interval (CI): 22.3, 29.0) with children ages two to four most at risk for the disease with 36.1% infected (95% CI: 30.1, 42.2). The defecation behaviors of an individual were more strongly associated with infection status than the household water and sanitation infrastructure, indicating the importance of incorporating behavior change into community-led total sanitation coverage.

Conclusions/Significance

Our results highlight the importance of incorporating monitoring and evaluation data into control programs in Uganda to understand the geographic distribution of schistosomiasis prevalence outside of communities where endemicity is known to be high. The high prevalence of schistosomiasis among the youngest age group, ineligible to receive drug treatment, shows the imperative to develop a child-appropriate drug protocol that can be safely administered to preschool-aged children. Water and sanitation interventions should be considered an essential investment for elimination alongside drug treatment.

Schistosomiasis is a neglected tropical disease in sub-Saharan Africa that has remained intractable despite efforts to eliminate it through mass drug administration. The transmission cycle is perpetuated when sanitation infrastructure does not adequately capture infected urine or feces and local water bodies, with snail vectors, are contaminated. Schistosomiasis has been linked with stunting and cognitive deficits and there is particular concern for the most vulnerable age group under five years old who are undergoing critical intestinal development but are ineligible to receive drug treatment. Efforts to reduce the disease have focused on children and young adolescents in endemic areas, near water bodies where transmission is known to be high. In Uganda, where fresh water bodies are abundant and intestinal schistosomiasis is endemic, very little is understood about the disease prevalence at a national level. We conducted a large, nationally representative survey and found a national prevalence of 25.6% where the 2–4 year old children had the highest prevalence for schistosomiasis with 36.1% infected. The most significant risk-factor for the disease was an individual’s open defecation behaviors in surface waters. This emphasizes the need to include water and sanitation investments alongside drug treatment and behavior change to control schistosomiasis in Uganda.

Multiplex Serologic Assessment of Schistosomiasis in Western Kenya: Antibody Responses in Preschool Aged Children as a Measure of Reduced Transmission

Currently, impact of schistosomiasis control programs in Schistosoma mansoni–endemic areas is monitored primarily by assessment of parasitologic indicators only. Our study was conducted to evaluate the use of antibody responses as a way to measure the impact of schistosomiasis control programs. A total of 3,612 serum samples collected at three time points from children 1–5 years of age were tested for antibody responses to two schistosome antigens (soluble egg antigen [SEA] and Sm25) by multiplex bead assay. The overall prevalence of antibody responses to SEA was high at baseline (50.0%). After one round of mass drug administration (MDA), there was minimal change in odds of SEA positivity (odds ratio [OR] = 1.02, confidence interval [CI] = 0.79–1.32, P = 0.89). However, after two rounds of treatment, there was a slight decrease in odds of SEA positivity (OR = 0.80, CI = 0.63–1.02, P = 0.08). In contrast to the SEA results, prevalence of antibody responses to Sm25 was lowest at baseline (14.1%) and higher in years 2 (19.8%) and 3 (18.4%). After one round of MDA, odds of Sm25 positivity increased significantly (OR = 1.51, CI = 1.14–2.02, P = 0.005) and remained significantly higher than baseline after two rounds of MDA (OR = 1.37, CI = 1.07–1.76, P = 0.01). There was a significant decrease in the proportion of 1-year-olds with positive SEA responses from 33.1% in year 1 to 13.2% in year 3 and a corresponding decrease in the odds (OR = 3.25, CI = 1.75–6.08, P < 0.001). These results provide preliminary evidence that schistosomiasis program impact can be monitored using serologic responses.