Estimating the population at risk with soil transmitted helminthiasis and annual drug requirements for preventive chemotherapy in Ogun State, Nigeria

Using ESPEN data for evidence-based control of neglected tropical diseases in sub-Saharan Africa: A comprehensive model-based geostatistical analysis of soil-transmitted helminths

BACKGROUND

The Expanded Special Project for the Elimination of Neglected Tropical Diseases (ESPEN) was launched in 2019 by the World Health Organization and African nations to combat Neglected Tropical Diseases (NTDs), including Soil-transmitted helminths (STH), which still affect over 1.5 billion people globally. In this study, we present a comprehensive geostatistical analysis of publicly available STH survey data from ESPEN to delineate inter-country disparities in STH prevalence and its environmental drivers while highlighting the strengths and limitations that arise from the use of the ESPEN data. To achieve this, we also propose the use of calibration validation methods to assess the suitability of geostatistical models for disease mapping at the national scale.

METHODS

We analysed the most recent survey data with at least 50 geo-referenced observations, and modelled each STH species data (hookworm, roundworm, whipworm) separately. Binomial geostatistical models were developed for each country, exploring associations between STH and environmental covariates, and were validated using the non-randomized probability integral transform. We produced pixel-, subnational-, and country-level prevalence maps for successfully calibrated countries. All the results were made publicly available through an R Shiny application.

RESULTS

Among 35 countries with STH data that met our inclusion criteria, the reported data years ranged from 2004 to 2018. Models from 25 countries were found to be well-calibrated. Spatial patterns exhibited significant variation in STH species distribution and heterogeneity in spatial correlation scale (1.14 km to 3,027.44 km) and residual spatial variation variance across countries.

CONCLUSION

This study highlights the utility of ESPEN data in assessing spatial variations in STH prevalence across countries using model-based geostatistics. Despite the challenges posed by data sparsity which limit the application of geostatistical models, the insights gained remain crucial for directing focused interventions and shaping future STH assessment strategies within national control programs.

Prevalence, intensity and risk factors of soil-transmitted helminthiasis after five effective rounds of preventive chemotherapy across three implementation units in Ondo State, Nigeria

BACKGROUND

Routine epidemiological data are essential for monitoring the effectiveness of preventive chemotherapy (PC), optimizing resource allocation, and addressing the evolving needs in the elimination of soil-transmitted helminthiasis (STH). This study assesses the prevalence, intensity, and associated risk factors of STH following five rounds of albendazole-based PC in three implementation units (IUs) in Ondo State, Nigeria.

METHODOLOGY

Fresh stool samples were collected from 2,093 children aged 5-14 years across 45 systematically selected schools in three IUs: Ese-Odo, Irele, and Ile-Oluji. The samples were analyzed using the Kato-Katz technique. Additionally, standardized questionnaires were administered to gather data on demographics and access to water, sanitation, and hygiene (WASH) resources. Data analysis was conducted using R software version 4.3.2, with a 95% confidence interval.

PRINCIPAL FINDINGS/CONCLUSIONS

The parasitological data indicated a significant decline in the aggregated prevalence of STH across the three IUs. In Ese-Odo, the prevalence decreased to 25.8% (95% CI: 23.0-29.0) from 39% at baseline (d = -34%, p = 0.00). In Irele, prevalence dropped to 9.7% (95% CI: 7.6-12.0) from 51.3% at baseline (d = -81%, p = 0.00), and in Ile-Oluji, prevalence was reduced to 6.4% (95% CI: 4.6-8.7) from 23% at baseline (d = -72.2%, p = 0.00). The most prevalent STH species was Ascaris lumbricoides, with infection rates of 25.5%, 9.4%, and 6.4% in Ese-Odo, Irele, and Ile-Oluji, respectively, followed by Trichuris trichiura in Ese-Odo (2.7%) and Irele (0.4%), while hookworm infections were detected only in Irele (0.7%). The majority of infections were of low intensity in Ese-Odo (91.0%), Irele (96.8%), and Ile-Oluji (100%). Access to improved sanitation (17.7%, 54.9%, and 58.2%), improved water sources (24.5%, 66.1%, and 69.8%), and handwashing facilities (9.0%, 39.6%, and 25.4%) was suboptimal and significantly varied across Ese-Odo, Irele, and Ile-Oluji, respectively (p < 0.05). Open defecation rates were high in Ese-Odo (54.2%), Irele (36.3%), and Ile-Oluji (34.3%). In Ese-Odo, significant risk factors for STH infection included the use of hand-pump boreholes (AOR: 2.44, 95% CI: 1.23-4.88, p = 0.01), unprotected dug wells (AOR: 3.25, 95% CI: 0.96-11.36, p = 0.06), ventilated improved pit latrines (AOR: 3.95, 95% CI: 1.13-16.1, p = 0.04), pit latrines without a slab (AOR: 2.19, 95% CI: 1.27-3.8, p = 0.01), and failure to use soap after defecation, both when soap was available (AOR: 12.09, 95% CI: 1.86-112.97, p = 0.01) and when soap was unavailable (AOR: 8.19, 95% CI: 1.73-76.65, p = 0.04). In Irele, access to protected dug wells was marginally significant (AOR: 1.79, 95% CI: 0.96-3.21, p = 0.06), while in Ile-Oluji, access to river water emerged as a significant risk factor (AOR: 7.97, 95% CI: 1.81-58.58, p = 0.02). The use of rainwater was found to be protective across all three IUs. These findings demonstrate significant progress in reducing STH prevalence across the three IUs following PC interventions. However, the data underscores the need for enhanced efforts to improve access to and use of WASH facilities to achieve STH elimination.

Understanding the impact of covariates on the classification of implementation units for soil-transmitted helminths control: a case study from Kenya

BACKGROUND

Soil-transmitted helminthiasis (STH) are a parasitic infection that predominantly affects impoverished regions. Model-based geostatistics (MBG) has been established as a set of modern statistical methods that enable mapping of disease risk in a geographical area of interest. We investigate how the use of remotely sensed covariates can help to improve the predictive inferences on STH prevalence using MBG methods. In particular, we focus on how the covariates impact on the classification of areas into distinct class of STH prevalence.

METHODS

This study uses secondary data obtained from a sample of 1551 schools in Kenya, gathered through a combination of longitudinal and cross-sectional surveys. We compare the performance of two geostatistical models: one that does not make use of any spatially referenced covariate; and a second model that uses remotely sensed covariates to assist STH prevalence prediction. We also carry out a simulation study in which we compare the performance of the two models in the classifications of areal units with varying sample sizes and prevalence levels.

RESULTS

The model with covariates generated lower levels of uncertainty and was able to classify 88 more districts into prevalence classes than the model without covariates, which instead left those as "unclassified". The simulation study showed that the model with covariates also yielded a higher proportion of correct classification of at least 40% for all sub-counties.

CONCLUSION

Covariates can substantially reduce the uncertainty of the predictive inference generated from geostatistical models. Using covariates can thus contribute to the design of more effective STH control strategies by reducing sample sizes without compromising the predictive performance of geostatistical models.

Community-based prevalence, intensity and risk factors associated with soil-transmitted helminthiases and intestinal schistosomiasis in Apojola, Ogun state, southwest Nigeria

BACKGROUND

Soil-transmitted helminthiases (STH) and schistosomiasis are parasitic neglected tropical diseases (NTDs) of significant public health importance globally, including Nigeria. Urogenital schistosomiasis is highly endemic in Apojola, a rural community in Ogun State, southwest Nigeria, but data on STH and intestinal schistosomiasis in the neglected community are lacking.

OBJECTIVES

To determine the prevalence and intensity of STH and intestinal schistosomiasis and the risk factors associated with the infections in Apojola.

METHODS

The study was community-based and cross-sectional. A structured questionnaire was used to obtain information on socio-demographic, personal, and household WASH characteristics of the study population. Stool samples were collected and processed for parasitological examination using the triplicate Kato-Katz (K-K) smears.

RESULTS

A total of 283 individuals (males, 50.2%; females, 49.8%) aged 3 to 65 years (mean age ± S.D.: 19.6 ± 14.8 years) participated in the study. No case of intestinal schistosomiasis was recorded in the study, while the overall prevalence of any STH was 38.2%: A. lumbricoides (24.0%) and hookworms (25.8%). Prevalence of infection was not significantly different between males and females for any STH (40.1% vs. 36.2%, χ2 = 0.473, p = 0.492); A. lumbricoides (23.2% vs. 22.7%, χ2 = 0.012, p = 0.913); or hookworms (28.2% vs. 23.4%; p = 0.360; χ2 = 0.839), but significantly varied with age for any STH (χ2 = 22.225, p = 0.002); A. lumbricoides (χ2 = 16.354, p = 0.022); or hookworms (χ2 = 20.001, p = 0.006). The intensity of infection was neither associated with gender nor age and was mostly light. Walking barefoot, toilet type (absent/bush), and irregular washing of fruits and/or vegetables before consumption were significantly associated with STH.

CONCLUSION

Our data indicate that intestinal schistosomiasis is not prevalent in Apojola and that the community is a moderate-risk area for STH. Hence, the current annual preventive chemotherapy for STH (PC STH) with albendazole or mebendazole in school-aged children (SAC) through the school-based delivery programme should be extended to non-enrolled SAC and pre-SAC using other delivery platforms. This should be complemented with regular and effective health education campaigns as well as water, sanitation, and hygiene (WASH)-related interventions.

Prevalence and determinants of double and triple burden of malnutrition among mother-child pairs in Malawi: a mapping and multilevel modelling study

OBJECTIVE

To establish the prevalence of double burden of malnutrition (DBM) and triple burden of malnutrition (TBM) among mother-child pairs in Malawi and explore their geographical distribution and associated multilevel factors.

DESIGN

Cross-sectional study using secondary data from the 2015-2016 Malawi Demographic and Health Survey using a mixed effects binomial model to identify multilevel factors associated with DBM and TBM. Georeferenced covariates were used to map the predicted prevalence of DBM and TBM.

SETTING

All twenty-eight districts in Malawi.

PARTICIPANTS

Mother-child pairs with mothers aged 15-49 years and children aged below 60 months (n 4618 pairs) for DBM and between 6 and 59 months (n 4209 pairs) for TBM.

RESULTS

Approximately 5·5 % (95% confidence interval (CI): 4·7 %, 6·4 %) of mother-child pairs had DBM, and 3·1 % (95 % CI: 2·5 %, 4·0 %) had TBM. The subnational-level prevalence of DBM and TBM was highest in cities. The adjusted odds of DBM were threefold higher (adjusted Odds Ratio, AOR: 2·8, 95 % CI: 1·1, 7·3) with a higher proportion of wealthy households in a community. The adjusted odds of TBM were 60 % lower (AOR: 0·4; 95 % CI: 0·2, 0·8) among pairs where the women had some education compared with women with no education.

CONCLUSIONS

Although the prevalence of DBM and TBM is currently low in Malawi, it is more prevalent in pairs with women with no education and in relatively wealthier communities. Targeted interventions should address both maternal overnutrition and child undernutrition in cities and these demographics.

Health workers' perspectives on school-based mass drug administration control programs for soil-transmitted helminthiasis and schistosomiasis in Ogun State, Nigeria

BACKGROUND

Soil-transmitted helminthiasis (STH) and schistosomiasis (SCH) are among the most prevalent neglected tropical diseases (NTDs), affecting 1.5 billion globally, with a significant burden in sub-Saharan Africa, particularly Nigeria. These diseases impair health and contribute to socio-economic challenges, especially in children, undermining educational and future economic prospects. The 2030 NTD Roadmap highlights Mass Drug Administration (MDA) as a critical strategy for controlling these NTDs, targeting vulnerable populations like school-age children. Despite some successes, challenges persist, indicating the need for deeper insights into program implementation. This study focuses on the perspectives of health workers implementing MDA in selected local government areas (LGAs) of Ogun State, Nigeria, aiming to identify challenges and enablers that align with the broader NTD 2030 goals.

METHODOLOGY/PRINCIPAL FINDINGS

The study used a qualitative research approach involving focus group discussions and in-depth interviews with health workers engaged in neglected tropical disease control programs in Ogun State, Nigeria, between July and September 2022. A semi-structured questionnaire guided the exploration of ideas, and the data were analyzed using the QRS Nvivo 12 software package. The study found that the school-based MDA control program's efficacy largely relies on strong collaborations and partnerships, particularly with educators, community heads, and other stakeholders. These alliances and strategic communication methods, like town announcements and media campaigns, have been pivotal in reaching communities. However, the program does grapple with hurdles such as parental misconceptions, limited funds, insufficient staffing, and misalignment with the Ministry of Education. It is recommended to boost funding, foster early stakeholder involvement, enhance mobilization techniques, and consider introducing a monitoring card system similar to immunization.

CONCLUSIONS/SIGNIFICANCE

The MDA Integrated Control Programs for STH and SCH in Ogun State schools demonstrate a holistic approach, integrating knowledge, collaboration, communication, and feedback. Health workers have shown commitment and adeptness in their roles. However, achieving maximum efficacy requires addressing critical barriers, such as parental misconceptions and funding challenges. Adopting the recommended strategies, including proactive communication, increased remuneration, and introducing a tracking system, can significantly enhance the program's reach and impact. The involvement of all stakeholders, from health workers to community leaders and parents, is essential for the program's sustainability and success.

Measuring heterogeneities in soil-transmitted helminth transmission and control

The global effort over the past decade to control soil-transmitted helminths (STH) has resulted in communities with endemic infection reaching low prevalence levels suitable for the validation of elimination as a public health problem (EPHP), defined by the World Health Organisation (WHO) as <2% of infections classified as moderate or heavy intensity. The spatial scale in which this is validated is currently undefined. As the burden of STH infection decreases, the degree of aggregation of infection within individuals in a population increases. Identifying these remaining pockets of infection requires fine-scale monitoring and evaluation (M&E) programmes that are rarely implemented within current national neglected tropical disease (NTD) control. This review examines various heterogeneities that characterise the epidemiology of STH infections, and discusses their impact on control policy formulation.

Soil-transmitted helminths: A critical review of the impact of co-infections and implications for control and elimination

Researchers have raised the possibility that soil-transmitted helminth (STH) infections might modify the host's immune response against other systemic infections. STH infections can alter the immune response towards type 2 immunity that could then affect the likelihood and severity of other illnesses. However, the importance of co-infections is not completely understood, and the impact and direction of their effects vary considerably by infection. This review synthesizes evidence regarding the relevance of STH co-infections, the potential mechanisms that explain their effects, and how they might affect control and elimination efforts. According to the literature reviewed, there are both positive and negative effects associated with STH infections on other diseases such as malaria, human immunodeficiency virus (HIV), tuberculosis, gestational anemia, pediatric anemia, neglected tropical diseases (NTDs) like lymphatic filariasis, onchocerciasis, schistosomiasis, and trachoma, as well as Coronavirus Disease 2019 (COVID-19) and human papillomavirus (HPV). Studies typically describe how STHs can affect the immune system and promote increased susceptibility, survival, and persistence of the infection in the host by causing a TH2-dominated immune response. The co-infection of STH with other diseases has important implications for the development of treatment and control strategies. Eliminating parasites from a human host can be more challenging because the TH2-dominated immune response induced by STH infection can suppress the TH1 immune response required to control other infections, resulting in an increased pathogen load and more severe disease. Preventive chemotherapy and treatment are currently the most common approaches used for the control of STH infections, but these approaches alone may not be adequate to achieve elimination goals. Based on the conclusions drawn from this review, integrated approaches that combine drug administration with water, sanitation and hygiene (WASH) interventions, hygiene education, community engagement, and vaccines are most likely to succeed in interrupting the transmission of STH co-infections. Gaining a better understanding of the behavior and relevance of STH co-infections in the context of elimination efforts is an important intermediate step toward reducing the associated burden of disease.