Impact of environmental factors on Biomphalaria pfeifferi vector capacity leading to human infection by Schistosoma mansoni in two regions of western Côte d'Ivoire.

ABSTRACT: BACKGROUND: Intestinal schistosomiasis remains a worrying health problem, particularly in western Côte d'Ivoire, despite control efforts. It is therefore necessary to understand all the factors involved in the development of the disease, including biotic and abiotic factors. The aim of this study was to examine the factors that could support the maintenance of the intermediate host and its vectorial capacity in western Côte d'Ivoire. METHODS: Data on river physicochemical, microbiological, and climatic parameters, the presence or absence of snails with Schistosoma mansoni, and human infections were collected between January 2020 and February 2021. Spearman rank correlation tests, Mann-Whitney, analysis of variance (ANOVA), and an appropriate model selection procedure were used to analyze the data. RESULTS: The overall prevalence of infected snails was 56.05%, with infection reaching 100% in some collection sites and localities. Of 26 sites examined, 25 contained thermophilic coliforms and 22 contained Escherichia coli. Biomphalaria pfeifferi was observed in environments with lower land surface temperature (LST) and higher relative air humidity (RAH), and B. pfeifferi infection predominated in more acidic environments. Thermal coliforms and E. coli preferred higher pH levels. Lower maximum LST (LST_Max) and higher RAH and minimum LST (LST_Min) were favorable to E. coli, and lower LST_Max favored coliforms. The presence of B. pfeifferi was positively influenced by water temperature (T °C), LST_Min, RAH, and precipitation (Pp) (P < 0.05) and negatively influenced by pH, total dissolved solids (TDS), electrical conductivity (EC), LST_Max, and mean land surface temperature (LST). The parameters pH, TDS, EC, LST_Min, LST, and Pp had a positive impact on snail infection, while LST_Max had a negative impact on infection. Only pH had a positive effect on coliform and E. coli abundance. Of the 701 people examined for human schistosomiasis, 73.13% were positive for the point-of-care circulating cathodic antigen (POC-CCA) test and 12.01% for the Kato-Katz (KK) test. A positive correlation was established between human infections and the abundance of Biomphalaria (r2 = 0.879, P = 0.04959). CONCLUSIONS: The results obtained reflect the environmental conditions that are conducive to the maintenance of S. mansoni infection in this part of the country. To combat this infection as effectively as possible, it will be necessary not only to redouble efforts but also to prioritize control according to the level of endemicity at the village level.

Improving the Cost-efficiency of Preventive Chemotherapy: Impact of New Diagnostics on Stopping Decisions for Control of Schistosomiasis.

BACKGROUND: Control of schistosomiasis (SCH) relies on the regular distribution of preventive chemotherapy (PC) over many years. For the sake of sustainable SCH control, a decision must be made at some stage to scale down or stop PC. These "stopping decisions" are based on population surveys that assess whether infection levels are sufficiently low. However, the limited sensitivity of the currently used diagnostic (Kato-Katz [KK]) to detect low-intensity infections is a concern. Therefore, the use of new, more sensitive, molecular diagnostics has been proposed. METHODS: Through statistical analysis of Schistosoma mansoni egg counts collected from Burundi and a simulation study using an established transmission model for schistosomiasis, we investigated the extent to which more sensitive diagnostics can improve decision making regarding stopping or continuing PC for the control of S. mansoni. RESULTS: We found that KK-based strategies perform reasonably well for determining when to stop PC at a local scale. Use of more sensitive diagnostics leads to a marginally improved health impact (person-years lived with heavy infection) and comes at a cost of continuing PC for longer (up to around 3 years), unless the decision threshold for stopping PC is adapted upward. However, if this threshold is set too high, PC may be stopped prematurely, resulting in a rebound of infection levels and disease burden (+45% person-years of heavy infection). CONCLUSIONS: We conclude that the potential value of more sensitive diagnostics lies more in the reduction of survey-related costs than in the direct health impact of improved parasite control.

How Does Treatment Coverage and Proportion Never Treated Influence the Success of Schistosoma mansoni Elimination as a Public Health Problem by 2030?

BACKGROUND: The 2030 target for schistosomiasis is elimination as a public health problem (EPHP), achieved when the prevalence of heavy-intensity infection among school-aged children (SAC) reduces to <1%. To achieve this, the new World Health Organization guidelines recommend a broader target of population to include pre-SAC and adults. However, the probability of achieving EPHP should be expected to depend on patterns in repeated uptake of mass drug administration by individuals. METHODS: We employed 2 individual-based stochastic models to evaluate the impact of school-based and community-wide treatment and calculated the number of rounds required to achieve EPHP for Schistosoma mansoni by considering various levels of the population never treated (NT). We also considered 2 age-intensity profiles, corresponding to a low and high burden of infection in adults. RESULTS: The number of rounds needed to achieve this target depends on the baseline prevalence and the coverage used. For low- and moderate-transmission areas, EPHP can be achieved within 7 years if NT ≤10% and NT <5%, respectively. In high-transmission areas, community-wide treatment with NT <1% is required to achieve EPHP. CONCLUSIONS: The higher the intensity of transmission, and the lower the treatment coverage, the lower the acceptable value of NT becomes. Using more efficacious treatment regimens would permit NT values to be marginally higher. A balance between target treatment coverage and NT values may be an adequate treatment strategy depending on the epidemiological setting, but striving to increase coverage and/or minimize NT can shorten program duration.

Status of selected biochemical and coagulation profiles and platelet count in malaria and malaria-Schistosoma mansoni co-infection among patients attending at Dembiya selected Health Institutions, Northwest Ethiopia.

Malaria and schistosomiasis are infectious diseases that cause coagulation disorders, biochemical abnormalities, and thrombocytopenia. Malaria and Schistosoma mansoni co-infection cause exacerbations of health consequences and co-morbidities.This study aimed to compare the effect of malaria and Schistosoma mansoni co-infection and malaria infection on selected biochemical and coagulation profiles, and platelet count. An institutional-based comparative cross-sectional study was conducted from March 30 to August 10, 2022. A total of 70 individuals were enrolled in the study using a convenient sampling technique. Wet mount and Kato Katz techniques were conducted to detect Schistosoma mansoni in a stool sample. Blood films were prepared for the detection of plasmodium. The data was coded and entered into EpiData version 3.1 before being analyzed with SPSS version 25. An independent t test was used during data analysis. A P-value of less than 0.05 was considered statistically significant. The mean [SD] of alanine aminotransferase, aspartate aminotransferase, creatinine, total bilirubin, and direct bilirubin in the co-infected was higher than in malaria infected participants. However, the mean of total protein and glucose in co-infected was lower than in the malaria infected participants. The mean of prothrombin time, international normalization ratio, and activated partial thromboplastin time in co-infected was significantly higher, while the platelet count was lower compared to malaria infected participants. Biochemical and coagulation profiles, and platelet count status in co-infection were changed compared to malaria infected participants. Therefore, biochemical and coagulation profiles and platelet count tests should be used to monitor and manage co-infection related complications and to reduce co-infection associated morbidity and mortality.

Malacological, socio-environmental evaluation, and evidence of local transmission and maintenance of schistosomiasis in an urban area of Northeast Brazil.

To present the current epidemiological scenario of schistosomiasis related to urban transmission through an epidemiological risk assessment in Porto de Galinhas, a coastal area of Pernambuco, Brazil. Malacological and parasitological surveys were performed between the years 2018 and 2020. Snails were identified taxonomically and examined to confirm infection by Schistosoma mansoni, and so to identify Schistosomiasis Transmission Foci (STF) by the artificial light exposure technique. Stool samples were examined using the Kato-Katz method to identify schistosomiasis cases. Socioeconomic, environmental, behavioural and health data were collected by a questionnaire applied to participates in the survey and used to predict the schistosomiasis risk occurrence by multivariate logistic regression. In all, a total of 6466 snails of Biomphalaria glabrata were collected and 36 breeding sites were identified, of which 25 % were STF. A total of 2236 individuals took part of the survey which identified 187 cases of schistosomiasis, registering a positivity percentage of 8.36 %. The surveys identified the neighbourhoods with the highest risk for transmission while the socioenvironmental analysis identifies other risk factors for disease occurrence, such as gender, age range, level of education and absence of water drainage. We found that areas with poor sanitation, flooding during winter periods and dwellings located near mangroves should be treated by health authorities as priority areas for health interventions to minimize disease transmission. In addition, efforts to improve the population's educational level could certainly contribute to the adoption of measures to prevent and control this neglected tropical disease.

Laboratory and field validation of the recombinase polymerase amplification assay targeting the Schistosoma mansoni mitochondrial minisatellite region (SmMIT-RPA) for snail xenomonitoring for schistosomiasis.

Improvements in diagnostics for schistosomiasis in both humans and snail hosts are priorities to be able to reach the World Health Organization (WHO) goal of eliminating the disease as a public health problem by 2030. In this context, molecular isothermal amplification tests, such as Recombinase Polymerase Amplification (RPA), are promising for use in endemic areas at the point-of-need for their accuracy, robustness, simplicity, and time-effectiveness. The developed recombinase polymerase amplification assay targeting the Schistosoma mansoni mitochondrial minisatellite region (SmMIT-RPA) was used to detect S. mansoni DNA from both laboratory and field Biomphalaria snails. Laboratory snails were experimentally infected and used at one, seven, and 28 days post-exposure (dpe) to 10 S. mansoni miracidia to provide samples in the early pre-patent infection stage. Field samples of Biomphalaria spp. were collected from the Mucuri Valley and Jequitinhonha Valley regions in the state of Minas Gerais, Brazil, which are endemic for S. mansoni. The sensitivity and specificity of the SmMIT-RPA assay were analysed and compared with existing loop-mediated isothermal amplification (LAMP), PCR-based methods, parasitological examination of the snails, and nucleotide sequencing. The SmMIT-RPA assay was able to detect S. mansoni DNA in the experimentally infected Biomphalaria glabrata as early as one dpe to 10 miracidia. It also detected S. mansoni infections (55.5% prevalence) in the field samples with the highest accuracy (100% sensitivity and specificity) compared with the other molecular tests used as the reference. Results from this study indicate that the SmMIT-RPA assay is a good alternative test to be used for snail xenomonitoring of S. mansoni due to its high sensitivity, accuracy, and the possibility of detecting early pre-patent infection. Its simplicity and portability also make it a suitable methodology in low-resource settings.

A cross-sectional pilot household study of Schistosoma mansoni burden and associated morbidities in Lake Albert, Uganda.

OBJECTIVES: Schistosomiasis is persistent in Lake Albert, Uganda, but local data are limited. This study aims to describe the local burden of moderate-to-heavy infection and associated morbidity in all ages and identify factors associated with these outcomes to guide further research. METHODS: This cross-sectional pilot study was conducted in July-August, 2022 in four village sites (Walukuba, Rwentale, Kyabarangwa and Runga) of the Praziquantel in Preschoolers (PIP) trial. Residents (approximately four per household) of any age of households of PIP participants were eligible, but individuals <10 years were only enrolled if no older individuals were available. Socio-demographic information, household location, single stool Kato-Katz and hepatic ultrasound results were obtained for a convenience sampled subset of trial households. The primary outcome, moderate-to-heavy infection (≥100 eggs per gram of faeces), was analysed using mixed-effects logistic regression, with a household random effect. Univariate analyses were used for the secondary outcome, periportal fibrosis (Niamey protocol ultrasound image pattern C-F). RESULTS: Of 243 participants with a median age of 22 (interquartile range 12-33) years from 66 households, 49.8% (103/207 with a Kato-Katz result) had moderate-to-heavy infection and 11.2% (25/224 with ultrasound data) had periportal fibrosis. Moderate-to-heavy infection clustered by household (intraclass correlation coefficient = 0.11) and, in multivariable analysis, varied by village (Walukuba vs. Kyabarangwa adjusted odds ratio [aOR] 0.11, 95% CI 0.02-0.71), was highest in participants aged 10-15 years (vs. 5-9 years aOR 6.14, 95% CI 1.61-23.38) and lower in those reporting praziquantel treatment in the past year (aOR 0.39, 95% CI 0.18-0.88). CONCLUSIONS: In this setting, schistosome infection and morbidity are pervasive in all age groups. More intensive interventions are needed, for example more frequent praziquantel treatment, under investigation in the PIP trial and improved water and sanitation. More research is needed to understand local treatment barriers and optimal control strategies.

Accuracy and precision of dried urine spot method for the detection of Schistosoma mansoni circulating cathodic antigens in resource-limited settings.

BACKGROUND: The World Health Organization recommends the use of Schisto point-of-care circulating cathodic antigens (Schisto POC-CCA) for screening of Schistosoma mansoni as it offers better sensitivity than microscopy. However, there are limitation facing the use of this method including timely availability of the test cassettes. The aim of this study was to determine the reliability of dried urine spot (DUS) method for collection of urine and detection of S. mansoni using Schisto POC-CCA cassettes in a resource-limited settings. METHODS: A cross-sectional study was conducted between October and November 2022 among 250 primary school children in Sengerema District, northwestern Tanzania. S. mansoni CCA was detected in filter paper-based DUS, liquid urine using DUS Schisto POC-CCA (index), and direct urine Schisto POC-CCA (comparator) methods respectively. S. mansoni eggs in stool were detected using duplicate Kato-Katz (KK) method. The measures of accuracy were computed and compared between the index and comparator methods. The strength of agreement between inter-raters precisions was tested using Cohen's kappa (k). RESULTS: This study revealed S. mansoni prevalence rates of 28.8%, 54.0% and 50.8% by duplicate KK, direct urine Schisto POC-CCA and DUS Schisto POC-CCA methods respectively. The mean intensity of infection among infected participants was 86.3 eggs per gram of stool (EPG) ranging from 12.0 EPG to 824.0 EPG. The sensitivity of DUS Schisto POC-CCA and direct urine Schisto POC-CCA was 94.44% (95% CI: 89.15-99.74%) and 97.22% (95% CI: 93.43-100.00%) respectively. The DUS Schisto POC-CCA method had slightly higher specificity (66.85%) than direct urine Schisto POC-CCA method (63.48%). The accuracy of the DUS Schisto POC-CCA was found to be slightly high (74.80%, 95% CI: 68.94-79.06%) compared to that of direct urine Schisto POC-CCA (73.20%, 95% CI: 67.25-78.59%). There was good agreement between two laboratory technologists who performed the DUS Schisto POC-CCA method on similar samples (k = 0.80, 95% CI: 0.59-0.95). CONCLUSIONS: The DUS Schisto POC-CCA method had comparable S. mansoni detection accuracy to direct urine Schisto POC-CCA. This suggests that the method could be a potential alternative to direct urine Schisto POC-CCA for screening S. mansoni in resource-limited situations.

Development of prediction models to identify hotspots of schistosomiasis in endemic regions to guide mass drug administration.

Schistosomiasis is a neglected tropical disease affecting over 150 million people. Hotspots of Schistosoma transmission-communities where infection prevalence does not decline adequately with mass drug administration-present a key challenge in eliminating schistosomiasis. Current approaches to identify hotspots require evaluation 2-5 y after a baseline survey and subsequent mass drug administration. Here, we develop statistical models to predict hotspots at baseline prior to treatment comparing three common hotspot definitions, using epidemiologic, survey-based, and remote sensing data. In a reanalysis of randomized trials in 589 communities in five endemic countries, a regression model predicts whether Schistosoma mansoni infection prevalence will exceed the WHO threshold of 10% in year 5 ("prevalence hotspot") with 86% sensitivity, 74% specificity, and 93% negative predictive value (NPV; assuming 30% hotspot prevalence), and a regression model for Schistosoma haematobium achieves 90% sensitivity, 90% specificity, and 96% NPV. A random forest model predicts whether S. mansoni moderate and heavy infection prevalence will exceed a public health goal of 1% in year 5 ("intensity hotspot") with 92% sensitivity, 79% specificity, and 96% NPV, and a boosted trees model for S. haematobium achieves 77% sensitivity, 95% specificity, and 91% NPV. Baseline prevalence is a top predictor in all models. Prediction is less accurate in countries not represented in training data and for a third hotspot definition based on relative prevalence reduction over time ("persistent hotspot"). These models may be a tool to prioritize high-risk communities for more frequent surveillance or intervention against schistosomiasis, but prediction of hotspots remains a challenge.

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.

Relationships Between Schistosoma mansoni Infection Intensity and Nutritional Status and Anemia Among Preschool-aged Children in Uganda.

In a cross-sectional analysis of 354 Ugandan children (age 12-48 months) infected with Schistosoma mansoni, we assessed relationships between infection intensity and nutritional morbidities. Higher intensity was associated with an increased risk for anemia (RR = 1.05, 95% confidence interval [CI] 1.01-1.10) yet not associated with risk for underweight, stunting, or wasting.

SEROPREVALENCE TO SCHISTOSOMA SOLUBLE EGG ANTIGEN AMONG NOMADIC PASTORALISTS RESIDING IN NORTHERN SENEGAL.

Urinary and intestinal schistosomiasis are endemic in Senegal, with prevalence heterogeneous throughout the country. Because of their way of life, nomadic pastoralists are not typically included in epidemiological surveys, and data on the prevalence of schistosomiasis in Senegalese nomadic populations are largely non-existent. The purpose of this study was to determine the seroprevalence of schistosomiasis in Senegalese nomadic pastoralists. A modified snowball sampling survey was conducted among 1,467 nomadic pastoralists aged 6 mo and older in 5 districts in northern Senegal. Dried blood spots from participants of all ages and data regarding demographics were collected to assess IgG antibody responses against Schistosoma mansoni soluble egg antigen (SEA) using a bead-based multiplex assay. Out of 1,467 study subjects, 1,464 (99.8%) provided IgG serological data that cleared quality assurance. Of the participants with appropriate data, 56.6% were male, the median age was 22 yr, and 31.6% were under 15 yr of age. The overall anti-SEA IgG seroprevalence was 19.1% (95% confidence interval [CI]: 17.1-21.1%) with the highest estimates observed in Dagana (35.9%) and the lowest observed in Podor nomadic groups (3.4%). Antibody responses increased significantly with age except for the oldest age groups (>40 yr of age), which saw lower levels of antibody response compared to younger adults. When controlling for age and location by multivariate regression, the male sex was associated with a 2-fold greater odds of anti-SEA IgG seropositivity (aPOR: 2.0; 95% CI: 1.5-2.7). Serosurveys for anti-SEA IgG among nomadic peoples in northern Senegal found a substantial percentage of individuals with evidence for current or previous Schistosoma spp. infection with the highest levels of exposure in the district adjacent to the Diama dam along the Senegal River. With IgG prevalence increased by age except in the older adults, and the male sex significantly associated with seropositivity, these data point toward sex-associated behavioral practices and human environmental modification as risk factors for Schistosoma exposure.

Variants of IL6, IL10, FCN2, RNASE3, IL12B and IL17B loci are associated with Schistosoma mansoni worm burden in the Albert Nile region of Uganda.

BACKGROUND: Individuals genetically susceptible to high schistosomiasis worm burden may contribute disproportionately to transmission and could be prioritized for control. Identifying genes involved may guide development of therapy. METHODOLOGY/PRINCIPAL FINDINGS: A cohort of 606 children aged 10-15 years were recruited in the Albert Nile region of Uganda and assessed for Schistosoma mansoni worm burden using the Up-Converting Particle Lateral Flow (UCP-LF) test detecting circulating anodic antigen (CAA), point-of-care Circulating Cathodic Antigen (POC-CCA) and Kato-Katz tests. Whole genome genotyping was conducted on 326 children comprising the top and bottom 25% of worm burden. Linear models were fitted to identify variants associated with worm burden in preselected candidate genes. Expression quantitative trait locus (eQTL) analysis was conducted for candidate genes with UCP-LF worm burden included as a covariate. Single Nucleotide Polymorphism loci associated with UCP-LF CAA included IL6 rs2066992 (OR = 0.43, p = 0.0006) and rs7793163 (OR = 2.0, p = 0.0007); IL21 SNP kgp513476 (OR 1.79, p = 0.0025) and IL17B SNP kgp708159 (OR = 0.35, p = 0.0028). A haplotype in the IL10 locus was associated with lower worm burden (OR = 0.53, p = 0.015) and overlapped SNPs rs1800896, rs1800871 and rs1800872. Significant haplotypes (p<0.05, overlapping significant SNP) associated with worm burden were observed in IL6 and the Th17 pathway IL12B and IL17B genes. There were significant eQTL in the IL6, IL5, IL21, IL25 and IFNG regions. CONCLUSIONS: Variants associated with S. mansoni worm burden were in IL6, FCN2, RNASE3, IL10, IL12B and IL17B gene loci. However only eQTL associations remained significant after Bonferroni correction. In summary, immune balance, pathogen recognition and Th17 pathways may play a role in modulating Schistosoma worm burden. Individuals carrying risk variants may be targeted first in allocation of control efforts to reduce the burden of schistosomiasis in the community.

Evaluation of isotype-based serology for diagnosis of Schistosoma mansoni infection in individuals living in endemic areas with low parasite burden.

Intestinal schistosomiasis is a chronic and debilitating disease that affects public health systems worldwide. Control interventions to reduce morbidity primarily involve the diagnosis and treatment of infected individuals. However, the recommended Kato-Katz (KK) parasitological method shows low sensitivity in individuals with low parasite loads and is not useful for monitoring elimination of parasite transmission at later stages. In the current study, we evaluated the accuracy of serum reactivity levels of different immunoglobulin isotypes in an enzyme-linked immunosorbent assay (ELISA), utilizing Schistosoma mansoni crude extracts, with the aim to improve the diagnosis of infected individuals with low parasite loads. The serum reactivity of IgM and IgG subclass antibodies (IgG1, IgG3, and IgG4) against soluble adult worm and egg antigen preparations was evaluated in residents from a schistosomiasis-endemic area in northern Minas Gerais, Brazil. The parasitological status of the study population was determined through fecal examination with multiple parasitological tests to create a consolidated reference standard (CRS) plus a fecal DNA detection test (q-PCR). Twelve months after praziquantel treatment, a second serum sample was obtained from the population for reexamination. A two-graph receiver operating characteristic curve (TG-ROC) analysis was performed using the serum reactivity of non-infected endemic controls and egg-positive individuals, and the cut-off value was established based on the intersection point of the sensibility and specificity curves in TG-ROC analyses. The diagnostic accuracy of each serological test was evaluated in relation to the parasitological CRS and to the combination of CRS plus qPCR results. The data revealed that serum reactivity of IgM and IgG3 against S. mansoni antigens did not allow identification of infected individuals from the endemic area. In contrast, serum IgG1 and IgG4-reactivity against schistosome antigens could distinguish between infected and non-infected individuals, with AUC values ranging between 0.728-0.925. The reactivity of IgG4 anti-soluble egg antigen - SEA (sensitivity 79 %, specificity 69 %, kappa = 0.49) had the best diagnostic accuracy, showing positive reactivity in more than 75 % of the infected individuals who eliminated less than 12 eggs per gram of feces. Moreover, serum IgG4 reactivity against SEA and against soluble worm antigen preparation (SWAP) was significantly reduced in the serum of infected individuals after 12 months of confirmed parasitological cure and in the absence of re-infection. These results reinforce that the described IgG4 anti-SEA ELISA assay is a sensitive alternative for the diagnosis of active intestinal schistosomiasis in individuals from endemic areas, including in those with a very low parasite load.

Prevalence of Soil-Transmitted Helminths and Schistosoma mansoni among Schoolchildren across Altitudinal Gradients in Amhara National Regional State, Ethiopia.

Soil-transmitted helminths (STHs) and Schistosoma mansoni infections are common parasitic infections in sub-Saharan Africa. Their distributions vary across altitudes in Ethiopia. Hence, ongoing updates of infection risk factors and prevalence data are necessary for successful intervention. A school-based, cross-sectional study was conducted from October to December 2019 involving 530 schoolchildren who were recruited by systematic random sampling from Amhara Regional State. A structured questionnaire was used to collect data on sociodemographic, geographical and environmental factors. Stool samples were collected and processed by Ritchie's and Kato Katz techniques. Data were entered into EpiData and analyzed using SPSS. Descriptive statistics were used to compute prevalence, and logistic regression was used to assess factors associated with STHs and S. mansoni infections. Variables with P < 0.05 were considered statistically significant. Among 530 schoolchildren, 169 (31.9%) and 78 (14.7%) were infected with STHs and S. mansoni, respectively. The prevalence of STHs (40.2%) in the semi-highlands and S. mansoni (30.4%) in the lowlands was high. Infrequent shoes wearing, exposure to soil, not washing vegetables before eating, and living outside in lowland areas were significantly associated with STHs infections (P < 0.05). Schoolchildren who fetched water to irrigate fields, swam in rivers, and lived in lowland areas were significantly associated with S. mansoni infection (P < 0.05). In conclusion, prevalence rates of STHs and S. mansoni infections differed across altitudes in Amhara Regional State. Therefore, current control strategies including deworming and provision of clean water and education on sanitation and hygiene should be intensified and adapted to the local context.

Update on the Geographic Distribution of the Intermediate Host Snails of Schistosoma mansoni on St. Lucia: A Step Toward Confirming the Interruption of Transmission of Human Schistosomiasis.

To provide information to guide considerations of declaring interruption of transmission of human schistosomiasis due to Schistosoma mansoni on St. Lucia, we undertook an island-wide survey in June-July 2022 to determine the presence of Biomphalaria snails, the intermediate hosts of S. mansoni, and their infection status. Snail surveys were carried out at 58 habitats to determine presence of Biomphalaria snails followed by examination of the collected snails for evidence of infection with S. mansoni. Furthermore, water samples were collected at the snail habitats and screened for presence of S. mansoni DNA using an eDNA approach. We found B. glabrata present in one habitat (Cul de Sac) where it was abundant. Specimens provisionally identified as Biomphalaria kuhniana were recovered from 10 habitats. None of the Biomphalaria specimens recovered were positive for S. mansoni. None of the eDNA water samples screened were positive for S. mansoni. Experimental exposures of both field-derived and laboratory-reared St. Lucian B. glabrata and B. kuhniana to Puerto Rican and Kenyan-derived S. mansoni strains revealed B. glabrata to be susceptible to both and B. kuhniana proved refractory from histological and snail shedding results. We conclude, given the current rarity of B. glabrata on the island and lack of evidence for the presence of S. mansoni, that transmission is unlikely to be ongoing. Coupled with negative results from recent human serological surveys, and implementation of improved sanitation and provision of safe water supplies, St. Lucia should be considered a candidate for declaration of interruption of human schistosomiasis transmission.

Seasonal patterns of Schistosoma mansoni infection within Biomphalaria snails at the Ugandan shorelines of Lake Albert and Lake Victoria.

Intestinal schistosomiasis is hyperendemic in many sub-Saharan African countries. In Uganda, it is endemic at both Lake Albert (LA) and Lake Victoria (LV) and caused by S. mansoni that uses Biomphalaria snails as obligatory intermediate snail hosts. To shed light on local patterns of infection, we utilised two PCR-based methods to detect S. mansoni within Biomphalaria spp. as collected at the Ugandan shorelines of Lake Albert and Lake Victoria from 2009-2010. Overall, at our Lake Albert sites, the mean infection prevalence was 12.5% (15 of 120 snails), while at our Lake Victoria sites the prevalence was 5% (3 of 60 snails). At our Lake Albert sites, the highest infection prevalence of 13.3% (8 of 60 snails) was at Walukuba, while at our Lake Victoria sites, the highest infection prevalence of 10% (2 of 20 snails) was at Lwanika. Three species of Biomphalaria, B. pfeifferi, B. stanleyi and B. sudanica, were identified at our Lake Albert collection sites, while only a single species, B. choanomphala, was identified at our Lake Victoria collection sites. Biomphalaria stanleyi (2 of 20 snails; 15%) had the highest infection prevalence, followed by B. sudanica (5 of 60 snails; 13.3%), B. pfeifferi (4 of 40 snails; 10%) and B. choanomphala (3 of 60 snails; 5%). Of the Biomphalaria species identified, B. choanomphala had the highest haplotype (gene) diversity score, followed by B. stanleyi, B. sudanica and B. pfeifferi. Sites with a higher mean prevalence of S. mansoni infection had higher intra-species haplotype diversity scores than sites with a lower mean prevalence. The wet seasons (LA: 13.3%; LV: 8.7%) had a consistently higher mean infection prevalence of S. mansoni than the dry seasons (LA: 9.5%; LV: 5%) for all species and all sites tested at both Lake Albert (n = 480) and Lake Victoria (n = 320), though the difference was not statistically significant.

Prevalence and risk factors of schistosomiasis and hookworm infection in seasonal transmission settings in northern Côte d'Ivoire: A cross-sectional study.

BACKGROUND: Schistosomiasis and hookworm infection remain public health problems in large parts of sub-Saharan Africa. The epidemiology of schistosomiasis and hookworm was studied in seasonal transmission settings in the northern part of Côte d'Ivoire. METHODOLOGY: In August 2018, a cross-sectional study was conducted. Urine and stool samples were collected from 742 individuals aged 6-96 years in 16 localities from four departments in northern Côte d'Ivoire. Urine samples were examined by a filtration method for quantification of Schistosoma haematobium eggs. Stool samples were subjected to duplicate Kato-Katz thick smears and eggs of Schistosoma mansoni and soil-transmitted helminths (STHs) were counted. Additionally, a questionnaire was administered to determine demographic characteristics and to identify risk factors of schistosomiasis and STHs. Malacologic surveys were carried out at water points that are contacted by humans and animals. PRINCIPAL FINDINGS: The prevalence of schistosomiasis was very low. Only two cases of S. mansoni were found (0.3%, 95% confidence interval [CI]: 0.1-1.0%). The distribution of S. haematobium was focal, with cases found only in two departments; Ferkessédougou (5.4%, 95% CI: 2.5-9.9%) and Ouangolodougou (2.7%, 95% CI: 0.9-6.3%). Hookworm was the only STH species observed with a prevalence of 1.5% (95% CI: 0.8-2.8%). A higher risk of S. haematobium infection was observed in males compared to females, but the difference was not statistically significant (2.3% versus 1.3%, odds ratio [OR]: 1.5, 95% CI: 0.8-2.7). Participants aged 16-20 years showed the highest prevalence of S. haematobium. A total of 111 human- and animal-water contact points were identified at 47 water sources. Three potential intermediate host snails of schistosomes were collected; namely, Bulinus forskalii (n = 761), Bulinus truncatus (n = 205), and Biomphalaria pfeifferi (n = 1). Yet, only one specimen of Bu. truncatus was found to be shedding schistosome cercariae. CONCLUSIONS/SIGNIFICANCE: This study confirms very low transmission of schistosomiasis and hookworm in northern Côte d'Ivoire. The establishment and rigorous implementation of integrated surveillance-response systems could lead to the elimination of schistosomiasis and hookworm in this part of Côte d'Ivoire.

Effect of environmental factors in reducing the prevalence of schistosomiasis in schoolchildren: An analysis of three extensive national prevalence surveys in Brazil (1950-2018).

BACKGROUND: Over seven decades, Brazil has made admirable progress in controlling schistosomiasis, and a frequent question about the explanation for this reduction refers to the effect of improving environmental factors in the country. This article seeks to identify factors related to the change in the epidemiological situation of schistosomiasis mansoni infection by analyzing three national prevalence surveys conducted since 1950. METHODOLOGY/PRINCIPAL FINDINGS: This is an ecological study analyzing an unbalanced panel of data based on national surveys and considering the municipality as the unit of analysis. The sample consisted of 1,721 Brazilian municipalities, in which a total of 1,182,339 schoolchildren aged 7-14 were examined during the three periods corresponding to each survey (1947-1953, 1975-1979, and 2010-2015). The percentage of municipalities with zero cases of schistosomiasis was: 45.4%, 54.2% and 73.7%, respectively for those periods. A zero-inflated Poisson regression model, with fixed and random effects, was fitted to assess the association between candidate factors and disease prevalence using a significance level of 5%. There was a significant decrease in disease prevalence between the first and last periods analyzed (RR 0.214, CI 0.184-0.249), with a protective association with access to sanitation (RR 0.996, CI 0.994-0.998), urbanization (RR 0.991, CI 0.989-0.993), and living in own households (RR 0.986, CI 0.983-0.989); and an inverse association with piped water supply (RR 1.010, CI 1.008-1.011). CONCLUSION: The findings of this study indicate a decrease in the prevalence of schistosomiasis over seven decades in schoolchildren from the analyzed Brazilian municipalities, associated with environmental factors and social conditions. The increased access to piped water in the municipalities apparently triggers other ways of contact with unsafe water bodies, generating new transmission routes and suggesting the need for a systemic approach concerning contact with water.

Schistosoma mansoni infection alters the host pre-vaccination environment resulting in blunted Hepatitis B vaccination immune responses.

Schistosomiasis is a disease caused by parasitic flatworms of the Schistosoma spp., and is increasingly recognized to alter the immune system, and the potential to respond to vaccines. The impact of endemic infections on protective immunity is critical to inform vaccination strategies globally. We assessed the influence of Schistosoma mansoni worm burden on multiple host vaccine-related immune parameters in a Ugandan fishing cohort (n = 75) given three doses of a Hepatitis B (HepB) vaccine at baseline and multiple timepoints post-vaccination. We observed distinct differences in immune responses in instances of higher worm burden, compared to low worm burden or non-infected. Concentrations of pre-vaccination serum schistosome-specific circulating anodic antigen (CAA), linked to worm burden, showed a significant bimodal distribution associated with HepB titers, which was lower in individuals with higher CAA values at month 7 post-vaccination (M7). Comparative chemokine/cytokine responses revealed significant upregulation of CCL19, CXCL9 and CCL17 known to be involved in T cell activation and recruitment, in higher CAA individuals, and CCL17 correlated negatively with HepB titers at month 12 post-vaccination. We show that HepB-specific CD4+ T cell memory responses correlated positively with HepB titers at M7. We further established that those participants with high CAA had significantly lower frequencies of circulating T follicular helper (cTfh) subpopulations pre- and post-vaccination, but higher regulatory T cells (Tregs) post-vaccination, suggesting changes in the immune microenvironment in high CAA could favor Treg recruitment and activation. Additionally, we found that changes in the levels of innate-related cytokines/chemokines CXCL10, IL-1ß, and CCL26, involved in driving T helper responses, were associated with increasing CAA concentration. This study provides further insight on pre-vaccination host responses to Schistosoma worm burden which will support our understanding of vaccine responses altered by pathogenic host immune mechanisms and memory function and explain abrogated vaccine responses in communities with endemic infections.