https://orcid.org/0000-0002-9339-9676
Figures
Abstract
Background
The backbone of Kenya’s soil-transmitted helminthiasis control program is the periodic distribution of anti-helminthic preventive chemotherapy (PC). PC distribution has been conducted since 2012 through the National School-Based Deworming Programme, which deworms school-age children (SAC, 5–14 years) living in areas at high risk for soil-transmitted helminth (STH) infections. After nearly a decade of deworming, the Ministry of Health sought to generate evidence for program monitoring by estimating the prevalence and intensity of STH infection in Narok and Bomet counties among at-risk groups: preschool-aged children (PSAC, 2–4 years), SAC, and women of reproductive age (WRA, 15–49 years), of which only SAC are covered by the deworming program.
Methods
During August and December of 2021, we conducted cross-sectional, population-based household surveys in Narok and Bomet counties, using multi-stage, cluster random sampling among resident PSAC, SAC, and WRA. Individual and household questionnaires were administered using an electronic mobile platform. Stool samples were collected and tested for roundworms (Ascaris lumbricoides), hookworms (Necator americanus, Ancylostoma duodenale), and whipworms (Trichuris trichura) using the Kato-Katz method.
Results
Stool samples were provided by 1,062 PSAC, 1,922 SAC, and 364 WRA. Results indicated that the prevalence of any STH infection in Bomet county was similar among SAC (16.2% [upper 95% design-corrected confidence interval [U95% CI]: 23.1%]) and PSAC (15.8% [U95% CI: 21.7%]). In Narok county, STH prevalence was marginally higher among PSAC (12.8% [U95% CI: 18.2%]) compared to SAC (11.3% [U95% CI: 16.2%]). Moderate-to-high intensity infection prevalence among PSAC and SAC exceeded the morbidity elimination threshold of 2% in both counties. A. lumbricoides and T. trichura were most identified; few hookworm infections were detected.
Conclusions
STH infections remain a public health problem in Narok and Bomet counties. There may be a need to expand PC distribution to include risk groups beyond SAC during deworming exercises, as envisioned in the Breaking Transmission Strategy, to hasten progress toward the achievement of STH as a public health problem.
Author summary
Soil-transmitted helminth (STH) infections, including roundworms (Ascaris lumbricoides), hookworms (Necator americanus, Ancylostoma duodenale), and whipworms (Trichuris trichura), have been shown to affect children’s nutrition and cognitive development. Monitoring the prevalence of STH infections among at-risk populations remains a key step in determining the type and frequency of deworming medication to administer. Globally, treatment guidelines recommend treating children and women of reproductive age (WRA), as they are at the highest risk of morbidity from infection. In Kenya, preventive chemotherapy (PC) administration has primarily targeted school-aged children (SAC) using a school-based delivery platform. However, program monitoring surveys demonstrated that the prevalence and intensity of STH infections among children continues to exceed the country’s elimination targets. Our results showed that in Narok and Bomet counties, the prevalence of any STH infection was moderate (10– < 20%) among children in both counties and low (2– < 10%) among WRA. This suggests the need to consider expanding PC administration to a community-based model to make significant strides toward eliminating soil transmitted helminths as a public health problem.
Citation: Kibati P, Wakesho F, Mwatha S, Mariga D, Ihahi J, Kioko D, et al. (2025) Prevalence and intensity of soil-transmitted helminth infections in Narok and Bomet Counties, Kenya: Evidence from program monitoring. PLoS Negl Trop Dis 19(12): e0012415. https://doi.org/10.1371/journal.pntd.0012415
Editor: jong-Yil Chai, Seoul National University College of Medicine, KOREA, REPUBLIC OF
Received: August 5, 2024; Accepted: December 5, 2025; Published: December 30, 2025
Copyright: © 2025 Kibati et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The data used for the analyses in this paper are owned by the government of Kenya, and are subject to provisions of the Data Protection Act https://kenyalaw.org/kl/fileadmin/pdfdownloads/LegalNotices/2021/LN263_2021.pdf. Researchers are welcome to request access to de-identified datasets from the Division of Vector-Borne and Neglected Tropical Diseases at the Ministry of Health (headdvbntd@gmail.com).
Funding: This research was funded by a grant provided to Children Without Worms (Georgia, USA) by Johnson and Johnson to support surveys conducted by the Division of Vector-Borne and Neglected Tropical Diseases, Ministry of Health, Kenya. The funders had no role in the survey design, data collection, data analysis, or interpretation. The findings and conclusions of the survey reflect the view of the authors only” as indicated on the manuscript.
Competing interests: I have read the journal’s policy and the authors of the manuscript have the following competing interests: KMS receives a salary from The Task Force for Global Health, an organization that receives funding from GSK and Johnson & Johnson, the manufacturers of albendazole and mebendazole, respectively.
Introduction
Soil-transmitted helminth (STH) infections caused by roundworms (Ascaris lumbricoides), hookworms (Necator americanus, Ancylostoma duodenale), and whipworms (Trichuris trichura) are a public health problem globally, predominantly in the poorest regions of the world [1,2]. The World Health Organization (WHO) classifies soil-transmitted helminthiasis among the neglected tropical diseases (NTDs) and it is estimated that STH affects more than 1.5 billion people globally [3]. In 2021, it was estimated that there were more than 640 million STH cases, resulting in more than 3400 deaths and 1.38 million disability-adjusted life years [4].
STHs cause human infection through the ingestion of eggs from contaminated food and soil or by active skin penetration in the case of hookworms [5]. STH infections are known to cause both acute and chronic disease conditions such as anaemia, malnutrition, abdominal pain and discomfort, diarrhoea, as well as impaired physical and cognitive development [5,6]. WHO recommends controlling morbidity caused by STH infections through preventive chemotherapy (PC) with the anthelmintic drugs albendazole or mebendazole [7].
In Kenya, STH infections are widely distributed, occurring mainly in western and southeastern coastal regions, as well as other localized areas [5,8,9]. According to Kenya’s 2016–2020 NTD strategic plan [10], it is estimated that 10 million people nationwide are affected by STH, with children accounting for 50%. Another 16.6 million people are deemed to be at risk of contracting STH infections [10–12]. The Ministry of Health, through the Division of Vector-Borne and Neglected Tropical Diseases, launched the Breaking Transmission Strategy in 2019, which aimed to eliminate morbidity due to STH infections [13]. This strategy seeks to integrate interventions by focusing on increasing coverage of mass drug administration (MDA), establishing sustainable implementation of necessary NTD-related water, sanitation, and hygiene interventions, and implementing behaviour change communication interventions that are necessary to move from control to elimination of STH infections as a public health problem [14].
The launch of the Breaking Transmission Strategy was necessitated by the fact that since 2012, PC has been provided by the National School-Based Deworming Programme targeting school-aged children (SAC, 5–14 years) in various parts of the country [15]. Within the first three years of implementation, the program demonstrated a reduction of moderate-to-heavy intensity (MHI) infection [15]. However, it was noted that STH reinfections remained common following treatment, suggesting the need for expanded interventions [16,17] and that, in areas of high prevalence, adults and children not in school acted as reservoirs of STH, thereby impeding the effectiveness of STH control programs through school-based interventions only [18,19].
Given this concern, in 2021, the Ministry of Health Kenya, through the Division of Vector-Borne and Neglected Tropical Diseases, sought to better understand the community-wide prevalence of infection. They selected two counties, Narok and Bomet, where there had been minimal reduction in STH prevalence among SAC, despite ongoing school-based deworming efforts spanning over five years [16]. This survey aimed to provide programmatic evidence supporting community-wide deworming by determining the point prevalence and intensity of STH infections among PSAC, SAC, and WRA in Narok and Bomet Counties [20–22].
Methods
Ethics statement
Ethical approval for the surveys was granted by the Ethics and Scientific Review Committee of AMREF Health Africa in Kenya (P 705 – 2019). Permission to collect data was obtained from the respective county/sub-county health offices. Participants and guardians were provided with information about the purpose of the survey and what to expect. Written informed consent by parents or guardians and verbal assent by participating children was obtained before enrolment. While this survey did not provide immediate treatment post-sample collection, all individuals and guardians of participating children received comprehensive health education regarding STH transmission, prevention and treatment availability through local health services.
Survey setting and population
The surveys were conducted in Narok and Bomet counties (Fig 1) in August and December 2021, respectively. These counties were purposefully selected due to their varying ecological and epidemiological contexts, historical PC administration through the National School Based Deworming Program from 2012, and ongoing concerns about persistent transmission of STH.
County and national boundaries were derived from openly licensed shapefiles provided by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) via the Humanitarian Data Exchange (HDX) platform (https://data.humdata.org/dataset/cod-ab-ken). Map created using R version 4.3.2, with ggplot2 on 28APR2022. Basemap Information: Kenya - Subnational Administrative Boundaries (https://data.humdata.org/dataset/cod-ab-ken); License: Creative Commons Attribution for Intergovernmental Organisations.
Narok County covers an area of 17,933 km2 with a population of roughly 1.2 million. The county is administratively divided into six sub-counties and 30 wards, each serving as smaller administrative sub-units of a sub-county [13].
Bomet County has an area of 2,037 km2 with a projected population of roughly 900,000. The county is divided into five sub-counties and 25 wards [23].
Survey design
We conducted a community-based, cross-sectional survey using a multi-stage cluster sampling approach following the Integrated Community-based Survey for Program Monitoring methodology. Similar sampling designs have been implemented in similar epidemiological studies in Uganda, Sierra Leone and Bangladesh [24–26]. Full methodological details can be found in the online reference manual (https://childrenwithoutworms.org/icspm-reference-manual/), with key details provided below.
The population-based, household surveys were conducted using a multi-stage, cluster random sampling technique, producing equal selection probabilities among resident PSAC, SAC, and WRA in the respective counties. Within each county, population and housing data from the Kenya National Bureau of Statistics, supplemented by county administrators, were used to identify the villages, which served as clusters [20]. Thirty clusters were randomly selected from each county in the first stage using population proportional to estimated size. The team selected clusters using the Survey Sample Builder developed by the Neglected Tropical Disease Support Centre at the Task Force for Global Health (https://childrenwithoutworms.org/icspm-survey-sample-builder-tool/).
The sample size for this survey was based on the transmission assessment survey methodology published by WHO, which recommends at least 332 participants for each at-risk group in a cluster survey [27,28]. Sample size calculation targeted the lowest precision adequate for assessing whether the prevalence of any STH infection had fallen below WHO thresholds for public health intervention [29,30].
To ensure the sample size was reached, 475 participants were selected for inclusion for each risk group in each county to accommodate an approximate non-response of 30%. Non-response was anticipated to cover both participants who did not consent to be surveyed and those who did not provide stool samples. Households were systematically selected using a pre-determined sampling interval, and the household selection form aided field teams in knowing which risk group was to be sampled from the household.
Recruitment and sample collection
Household members of selected households were included if they: a) were a member of the selected risk groups of interest (PSAC, SAC, and WRA), b) slept at the household the night before the interview, c) planned to stay at the household the night of the interview, d) were able to provide a single stool sample within 24 hours of the interview, and e) were able and willing to provide verbal consent or assent.
On the survey day, field officers visited the selected households, and explained the purpose of the survey and ensured consent/assent was obtained. The field teams were comprised of a national-level supervisor from the Ministry of Health, a county-level supervisor, a community health assistant (CHA) from the area, and a community health volunteer (CHV) from the village being visited. Each participant was assigned a unique identification number, which was used to track the collected sample and link it to the individual information collected during the household visit. Participants were interviewed by trained data collectors using a pre-tested, structured questionnaire. Socio-demographic information on the household was provided by the household head/designate, and everyone provided their individual-level information. Information for young children was provided by the household head/designate.
The participants were given a labelled wide-mouthed plastic container for stool collection, a piece of plain paper, a piece of applicator sticks, and other sanitary necessities such as tissue paper. The plastic containers were labelled with the participants’ unique identification numbers and their name, age, and sex to ensure a mix-up of containers did not occur within the household. The survey information was given to the head of household or his designate if the household head was absent. If the household head was not conversant in English, the community health assistant explained the instructions in the local language. The field team explained safe stool collection to the participant and asked them to wash their hands with soap and water after providing samples. The fresh stool samples were collected the morning after the household visit and interview.
Laboratory procedure
Stool samples were transported to the laboratory using cooler boxes within three hours of collection. To address the recognized sensitivity limitations of the Kato-Kats technique, particularly for hookworm detection due to rapid egg degradation in low transmission settings, we established mobile laboratories at the nearest health centre to minimize specimen transport time [27]. Stool samples were then prepared using a 41.7 mg Kato-Katz template, with duplicate slides prepared and read by two laboratory technicians under microscopes [22]. To maintain quality assurance, 10% of the slides were randomly selected and examined by a third technician blinded from the initial results from the other technicians.
Classification of infection intensity
The infection intensity, commonly called worm burden, is typically measured indirectly by counting the number of eggs in faeces, expressed as eggs per gram (epg). This is because indirect methods are more convenient and less invasive [24]. Direct methods of classifying worm burden, which involve counting the number of expelled worms after anti-helminthic treatment, may not be feasible during mass surveys and in areas with low worm burden.
WHO classifies infection intensity as light, moderate, or heavy using indirect methods for each type of STH [24]. The epg estimate was applied to categorize the samples based on infection intensity following WHO guidelines. For A. lumbricoides infections, light intensity was defined as 1–4,999 epg, moderate intensity as 5,000–49,999 epg, and heavy intensity as ≥50,000 epg. T. trichiura infections were classified as light intensity with 1–999 epg, moderate intensity with 1,000–9,999 epg, and heavy intensity with ≥10,000 epg. For hookworm infections, light intensity was defined as 1–1,999 epg, moderate intensity as 2,000–3,999 epg, and heavy intensity as ≥4,000 epg.
Data collection and management
Data were collected via mobile phone using Open Data Kit [ODK] and uploaded to a central secure server. Three data sets [individual, household, and laboratory] were downloaded from the server and saved on computers at the Ministry of Health Kenya. Using Microsoft Excel, the data were cleaned, and the household and individual files were merged with unique household identification numbers and later with the laboratory file’s unique individual identification numbers.
Data analysis
The cleaned dataset was imported into SAS version 9.04 and R version 4.13 to manage and analyze the data.. In line with the ICSPM survey methodology, the point prevalence and intensity of STH infections were estimated separately for each parasite species and stratified by county and risk group. We reported one-sided upper 95% confidence intervals (U95%CI) as the survey was designed to determine the lowest threshold under which true prevalence lies.
Results
Characteristics of survey population
The survey teams visited 60 villages/clusters in the two counties, with 30 surveyed in each Bomet and Narok. However, due to an electronic data collection issue, participant information from one village in Narok County was lost. A total of 3,348 (48% male, 51% female and 1% unreported) individuals were enrolled in the surveys, of whom 2,335 (69.7%) provided stool samples (Table 1).
Among the 2,096 children providing a stool sample, 1,034 (49.3%) were female, and the median age was 3 years for PSAC (interquartile range [IQR]:2–4), 9 years for SAC (IQR:7–12), and 29 years for WRA (IQR: 20–40).
Prevalence of infection
The prevalence of infections appeared to be slightly higher in Bomet County than in Narok County across all risk groups (Table 2). Among children (PSAC and SAC), the estimated prevalences ranged from 11% to 13% in Narok County and approximately 16% in Bomet County. Among WRA, in both counties, the prevalence of any STH infection was less than 10%, with Narok at 6.6% and Bomet at 8.1%.
In both counties, the prevalence of MHI infection among children was above the 2% threshold for elimination as a public health problem. Children in Bomet County appeared to have higher MHI infection prevalence among both PSAC (6.1%) and SAC (5.5%) than corresponding risk groups in Narok County. WRA in Bomet County recorded the lowest prevalence (0.7%) among all risk groups.
Parasite type
In both counties, A. lumbricoides caused the most infections, followed by T. trichura. Hookworm infections were not detected in Bomet County and were uncommon in Narok County. In Bomet County, the prevalence of A. lumbricoides infections was slightly higher among SAC, followed by PSAC, then WRA. In Narok County, T. trichura infections followed this pattern; however, unlike Bomet County, the prevalence of A. lumbridcoides was shown to be higher among PSAC than SAC.
Co-infections
Co-infections were uncommon (Table 3). When identified, they were most frequently A.lumbricoides and T.trichura, with all risk groups in both counties recording at least one co-infection. No triple infections were detected.
Discussion
Our findings underscore persistent transmission of STH, evidenced by moderate (10– < 20%) STH infection prevalence among children in Bomet and Narok Counties. Prevalence estimates of any STH infection were above the 2% treatment threshold target according to the breaking transmission strategy [31], and the prevalence of MHI infections also exceeded the WHO 2030 target for elimination as a public health problem (<2%) among all surveyed children [7]. These findings are consistent with recent findings from geostatistical modelling of STH using a nationwide survey dataset that showed a high probability of sub counties in the southwestern part of Kenya where Narok and Bomet are located exceeding the 2% and 10% prevalence threshold for A.lumbricoides and T.trichura [32].
These results are critical for informing programmatic decisions, particularly on the continuation of MDAs. While the 2% threshold is an established benchmark for guiding such interventions, its interpretation must consider local transmission dynamics [33,34]. Similar patterns of persistent infection despite continued PC among SAC have been highlighted in other studies, reflecting the relative slow decline of infections despite continued school based deworming [35–37]. These findings suggest that tailoring of continued annual PC in these counties is required to make progress toward the elimination of STH morbidity as a public health problem in the country.
Compared to prior surveys, the estimated prevalences among SAC from our community-based surveys (Bomet, 16.2%, and Narok, 11.3%) were lower than those demonstrated by school-based impact surveys conducted in 2017, five years after the commencement of the National School-Based Deworming Programme. These 2017 surveys showed a reduction of STH among SAC in Bomet from 29.7% in 2012 to 18.1% in 2017 and, in Narok, from 53% in 2012 to 41% in 2017 [16]. However, the prevalences are higher than those derived from the ten-year model based geostatistical impact surveys (Bomet 8.3%, and Narok 10.8%) conducted between 2021 and 2022 [25]. Despite there being an overall decline in the prevalence of STH from baseline in the country, the rate of decline in these two counties has been relatively lower, which could be explained by poor sanitation facilities, resulting in possible re-infection [26].
Parasite species
A. lumbricoides was the most common STH infection observed in the two counties, followed by T. trichura, with very few hookworm infections detected. This finding corresponds with school-based surveys conducted by the National School-based Deworming Programme, which found A. lumbricoides to be the most common STH during baseline, midline, and end-line surveys in the country as well as geostatistical modelling that showed A.lumbricoides and T.trichura to be prevalent in these areas [18,32]. This may be due to helminths’ long lifespan in human hosts and their production of many environmentally resistant eggs, which are expelled in faeces to enhance their survival and lifecycle continuation, leading to reinfection [17,38].
The survey also concurs with findings from the National School-based Deworming Programme that did not show significant reductions in the prevalence of MHI infection with T. trichura, where albendazole is the drug distributed. In contrast, it has been shown that a combination of ivermectin and albendazole would be the drug of choice in areas with high T. trichura infections [26,39], and WHO now suggests including ivermectin in addition to albendazole in such settings [40,41]. Drugs such as emodepside are also currently being tested in humans and show great promise as alternative treatments to address the limited effectiveness of benzimidazoles against T. trichiura [42].
It is also possible that reinfection occurs among the at-risk age groups, resulting in a resurgence of prevalence, as stated in a meta-analysis that showed infection after treatment occurs rapidly, particularly for A. lumbricoides and T.trichura [17].
Risk groups targeted by PC
Both infection prevalence and MHI infection prevalence were similar among PSAC and SAC within both counties. The consistency in high prevalence among PSACs who are routinely excluded from PC distributions highlights the fact that they should be considered for targeting during deworming exercises, as infections among this age group may lead to morbidity and cognitive impairment and may compromise the performance of PSAC on expressive language [38].
In addition, given the prevalence of similar magnitude among PSAC and SAC, the Ministry may consider expanding beyond school-based PC to include other at-risk groups, such as PSAC and WRA, to achieve broader community impact, as shown in studies from western and coastal Kenya and Malawi [32,41,43,44]. This expansion beyond SAC may enable the country to accelerate progress toward eliminating STH as a public health problem in line with the Breaking Transmission Strategy and the WHO 2030 NTD Road Map, similar to the approach taken by Kenya to conduct community wide mapping in the coastal part of Kenya, coupled with higher coverage rates and the ability of reaching non-enrolled SAC through community wide MDAs [9,45]. While Kenya has implemented community wide MDAs in select parts of the country, additional evaluation of its cost effectiveness relative to other delivery models could guide programmatic decisions to determine the most feasible strategy for progressing towards elimination.
Limitations
The survey was designed to estimate prevalence based on county-level administrative boundaries. However, intra-county prevalence heterogeneity is likely. While subgroup comparative analyses were not conducted for this study, as the ICSPM methodology prioritizes population-level classification rather than inferential analyses, this could be explored in future work. Hence, the program was not able to consider the diversity of the ecological conditions that have implications on the drivers of STH transmission within the counties, contributing to the heterogeneous classification of infection. In addition, the study did not assess individual, behavioural or environmental risk factors. This may limit interpretation of the observed intra-county heterogeneity limiting insights into drivers of transmission. This, in turn, would affect decision-making as to where PC distribution would be most efficient and cost-effective for the program. Subsequently, with these results, PC administration would be conducted in the entire county and not in specific focal areas with a prevalence above 2%, contrary to the BTS, which stipulates that the implementation unit for treatment is the ward.
The sensitivity of the Kato Katz technique in detecting hookworm eggs is reduced in low-prevalence settings and with sample transportation delays between the time of collection in the field and analysis in the laboratory. Even under optimal conditions, its diagnostic sensitivity remains low for hookworm, with studies showing that this method may substantially underestimate true infection prevalence [46–48]. This ought to be considered when interpreting programmatic interpretation of prevalence estimates. However, to mitigate this risk, laboratories were established at the nearest health centres where teams were conducting the survey. This significantly reduced the time between sample collection and laboratory analysis. Delays in sample shipment would lead to an underestimation of the true prevalence of hookworm infections in the sampled population [27,28]. In addition, some participants who were provided with stool pots didn’t provide samples. However, the number was not significant as the sample size for the study was still achieved.
During the survey conducted in Narok County, data from one village was lost, reducing the sample size. This loss may have influenced the STH prevalence estimate in the county. However, it’s anticipated that any shifts in the county-level prevalence would likely be minimal given that data from the missing village represent approximately 1/30th of the total sample size.
Conclusion
Our survey showed that STH infections remain a public health problem in Narok and Bomet counties. The elevated infection prevalence and MHI infection prevalence among all surveyed groups, including PSAC and WRA, suggest that expansion to risk groups beyond SAC during deworming exercises, as envisioned in the Breaking Transmission Strategy, may accelerate progress to controlling STH infections.
Acknowledgments
We thank the children and parents who participated in this survey, and the supervision and technical support from the Division of Vector-Borne and Neglected Tropical Diseases, Children Without Worms, and the African Field Epidemiology Network [AFENET]. We are grateful to the field officers who collected the data and the data team who worked tirelessly to ensure the survey was completed. We acknowledge the support from the national and county management in Bomet and Narok counties.
References
- 1.
WHO. Ending the neglect to attain the Sustainable Development Goals: a road map for neglected tropical diseases 2021–2030. Geneva: World Health Organization; 2020. p. 196. Available from: https://www.who.int/neglected_diseases/Revised-DraftNTD-Roadmap-23Apr2020.pdf
- 2.
Id R, Mpanya A, Inocencio R, Id SL, Id EH, Boelaert M. Community-based survey on helminth infections in Kwilu province, the Democratic Republic of the Congo, and implications for local control strategies. 2020:1–14.
- 3. Brooker S. Estimating the global distribution and disease burden of intestinal nematode infections: adding up the numbers--a review. Int J Parasitol. 2010;40(10):1137–44. pmid:20430032
- 4. Chen J, Gong Y, Chen Q, Li S, Zhou Y. Global burden of soil-transmitted helminth infections, 1990–2021. Infect Dis Poverty. 2024;13(1).
- 5. Jourdan PM, Lamberton PHL, Fenwick A, Addiss DG. Seminar soil-transmitted helminth infections. The Lancet. 2017;6736(17):1–14.
- 6.
Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. 2006;367.
- 7.
World Health Organization (WHO). 2030 targets for soil-transmitted helminthiases control programmes. 2012.
- 8.
Pullan RL, Gething PW, Smith JL, Mwandawiro CS, Sturrock HJW, Gitonga CW, et al. Spatial modelling of soil-transmitted helminth infections in Kenya: a disease control planning tool. 2011;5(2).
- 9. Kepha S, Ochol D, Wakesho F, Omondi W, Njenga SM, Njaanake K, et al. Precision mapping of schistosomiasis and soil-transmitted helminthiasis among school age children at the coastal region, Kenya. PLoS Negl Trop Dis. 2023;17(1):e0011043. pmid:36602986
- 10.
Ministry of Health Kenya. The 2nd Kenya National Strategic Plan For control of Neglected Tropical Diseases 2016-2020. 2020.
- 11. Ng’ang’a M, Matendechero S, Kariuki L, Omondi W, Makworo N, Owiti PO, et al. Burden of Soil Transmitted Helminthiasis in Primary School Children in Migori County, Kenya. East African Med J. 2016;93(10):32–9.
- 12.
Ministry of Health Kenya. The 2nd Kenya National Strategic Plan For control of Neglected Tropical Diseases. 2015.
- 13. Pullan RL, Halliday KE, Oswald WE, Mcharo C, Beaumont E, Kepha S, et al. Effects, equity, and cost of school-based and community-wide treatment strategies for soil-transmitted helminths in Kenya: a cluster-randomised controlled trial. The Lancet. 2019;393(10185):2039–50.
- 14.
Anderson RM, Turner HC, Truscott JE, Hollingsworth TD. Should the goal for the treatment of soil transmitted helminth (STH) infections be changed from morbidity control in children to community-wide transmission elimination? 2020:1–8.
- 15. Okoyo C, Nikolay B, Kihara J, Simiyu E, Garn JV, Freeman MC, et al. Monitoring the impact of a national school based deworming programme on soil-transmitted helminths in Kenya: The first three years, 2012 - 2014. Parasit Vectors. 2016;9(1):1–13.
- 16.
Mwandawiro C, Okoyo C, Kihara J, Simiyu E, Kepha S, Campbell SJ. Results of a national school-based deworming programme on soil-transmitted helminths infections and schistosomiasis in Kenya: 2012 – 2017. 2019:1–18.
- 17.
King CH, Zhou XN, Jia TW, Melville S. Soil-Transmitted Helminth Reinfection after Drug Treatment: A Systematic Review and Meta-Analysis. 2012;6(5).
- 18.
Njenga SM, Mwandawiro CS, Muniu E, Mwanje MT, Haji FM, Bockarie MJ. Adult population as potential reservoir of NTD infections in rural villages of Kwale district, Coastal Kenya: implications for preventive chemotherapy interventions policy. 2011;2–7.
- 19.
Njenga SM, Mutungi FM, Wamae CN, Mwanje MT, Njiru KK, Bockarie MJ. Once a year school-based deworming with praziquantel and albendazole combination may not be adequate for control of urogenital schistosomiasis and hookworm infection in Matuga District, Kwale County, Kenya. 2014:1–9.
- 20. Halliday KE, Oswald WE, Mcharo C, Beaumont E, Gichuki PM, Kepha S, et al. Community-level epidemiology of soil-transmitted helminths in the context of school-based deworming: Baseline results of a cluster randomised trial on the coast of Kenya. PLoS Negl Trop Dis. 2019;13(8):e0007427. pmid:31398204
- 21.
Narok County Government. Narok County Integrated Development Plan 2018-2022. 2022;1–52.
- 22.
County Government of Bomet. County Government of Bomet County Integrated Development Plan 2018-2022. 2018:518.
- 23.
Anderson RM, Turner HC, Truscott JE, Hollingsworth TD. Should the goal for the treatment of soil transmitted helminth (STH) infections be changed from morbidity control in children to community-wide transmission elimination? 2020;1–8.
- 24. Tupps C, Kargbo-Labour I, Paye J, Dhakal S, Hodges MH, Jones AH, et al. Community-wide prevalence and intensity of soil-transmitted helminthiasis and Schistosoma mansoni in two districts of Sierra Leone. PLoS Negl Trop Dis. 2022;16(5).
- 25. Davlin SL, Jones AH, Tahmina S, Al KA, Joshi A, Zaman SI, et al. Soil-transmitted helminthiasis in four districts in Bangladesh: household cluster surveys of prevalence and intervention status. BMC Public Health. 2020;20(1).
- 26. Tinkitina B, Beinamaryo P, Kyarisiima H, Nabatte B, Arinaitwe M, Mubangizi A. Prevalence and intensity of soil-transmitted helminth infections among school-aged children in five districts in Uganda. PLoS Negl Trop Dis. 2024;18(8).
- 27. Nikolay B, Brooker SJ, Pullan RL. Sensitivity of diagnostic tests for human soil-transmitted helminth infections: A meta-analysis in the absence of a true gold standard. Int J Parasitol. 2014;44(11):765–74.
- 28. Katz N, Chaves A, Pellegrino J. A simple device for quantitative stool thick-smear technique in Schistosomiasis mansoni. Rev Inst Med Trop Sao Paulo. 1972;14(6):397–400. pmid:4675644
- 29.
Jones A. Integrated Community-Based Survey for Program Monitoring (ICSPM) Reference Manual, version 2.2 Integrated Community-Based Survey for Program Monitoring, version 2.2 ii incorporates input from CWW staff on lessons learned in the first ICSPMs in Bangladesh. adds Annexes 12 and 13 and incorporates comments adds selection probabilities to Annex 4 for SAC and WRA. This manual and other program tools prepared by CWW can be downloaded at childrenwithoutworms.org/icspm-manual-resources. 2017.
- 30. World Health Organization. Assessing the epidemiology of soil-transmitted helminths during a transmission assessment survey (TAS) [Internet]. 2015 [cited 2025 Apr 26]. Available from: https://www.who.int/publications/i/item/9789241508384
- 31.
Ministry of Health Kenya. The Kenya national breaking transmission strategy for soil-transmitted helminthiasis, schistosomiasis, lymphatic filariasis and trachoma. 2019.
- 32. Truscott JE, Hardwick RJ, Werkman M, Saravanakumar PK, Manuel M, Ajjampur SSR, et al. Forecasting the effectiveness of the DeWorm3 trial in interrupting the transmission of soil-transmitted helminths in three study sites in Benin, India and Malawi. Parasit Vectors. 2021;14(1).
- 33. Mutono N, Njuguna B, Kepha S, Wakesho F, Omondi W, Kibati P, et al. Geostatistical modelling of soil-transmitted helminth prevalence in Kenya: Informing targeted interventions to accelerate elimination efforts. Int J Infect Dis. 2025;156:107916. pmid:40311799
- 34. Werkman M, Wright JE, Truscott JE, Easton AV, Oliveira RG, Toor J. Testing for soil-transmitted helminth transmission elimination: Analysing the impact of the sensitivity of different diagnostic tools. PLoS Negl Trop Dis. 2018;12(1).
- 35. Masaku J, Okoyo C, Araka S, Musuva R, Njambi E, Njomo DW, et al. Understanding factors responsible for the slow decline of soil-transmitted helminthiasis following seven rounds of annual mass drug administration (2012–2018) among school children in endemic counties of Kenya: A mixed method study. PLoS Negl Trop Dis. 2023;17(5).
- 36. Burnim M, Ivy JA, King CH. Systematic review of community-based, school-based, and combined delivery modes for reaching school-aged children in mass drug administration programs for schistosomiasis. PLoS Negl Trop Dis. 2017;11(10).
- 37.
Okoyo C, Minnery M, Orowe I, Owaga C, Wambugu C, Olick N, et al. Using a model-based geostatistical approach to design and analyse the prevalence of schistosomiasis in Kenya. 2023;2023:1–10.
- 38.
Kenya National Bureau of Statistics. Kenya Population and Housing Census 2019 Volume III. Vol. 21. 2020. p. 1–9.
- 39. Hürlimann E, Keller L, Patel C, Welsche S, Hattendorf J, Ali SM, et al. Efficacy and safety of co-administered ivermectin and albendazole in school-aged children and adults infected with Trichuris trichiura in Côte d’Ivoire, Laos, and Pemba Island, Tanzania: a double-blind, parallel-group, phase 3, randomised controlled trial. Lancet Infect Dis. 2022;22(1):123–35. pmid:34856181
- 40.
World Health Organization. Assessing schistosomiasis and soil-transmitted helminthiases control programmes Monitoring and evaluation framework. 2024.
- 41. Mazibuko XI, Chimbari M. The effect of schistosomiasis and soil-transmitted helminths on expressive language skills among African preschool children. BMC Infect Dis. 2022;22(1):264. pmid:35303827
- 42. Makaula P, Kayuni SA, Mamba KC, Bongololo G, Funsanani M, Juziwelo LT, et al. Mass drug administration campaigns: comparing two approaches for schistosomiasis and soil-transmitted helminths prevention and control in selected Southern Malawi districts. BMC Health Serv Res. 2024;24(1).
- 43. Krücken J, Holden-Dye L, Keiser J, Prichard RK, Townson S, Makepeace BL, et al. Development of emodepside as a possible adulticidal treatment for human onchocerciasis - the fruit of a successful industrial-academic collaboration. PLoS Pathogens. 2021;17.
- 44. Mwinzi PNM, Montgomery SP, Owaga CO, Mwanje M, Muok EM, Ayisi JG, et al. Integrated community-directed intervention for schistosomiasis and soil transmitted helminths in western Kenya - a pilot study. Parasit Vectors. 2012;5:182. pmid:22937890
- 45. Masaku J, Okoyo C, Araka S, Musuva R, Njambi E, Njomo DW, et al. Understanding factors responsible for the slow decline of soil-transmitted helminthiasis following seven rounds of annual mass drug administration (2012 – 2018) among school children in endemic counties of Kenya: A mixe. PLOS Negl Trop Dis. 2023:1–29.
- 46.
World Health Organization (WHO). Preventive chemotherapy guideline to control soil-transmitted helminth infections in at-risk population groups. 2017.
- 47.
Loukas A, Hotez PJ, Diemert D, Yazdanbakhsh M, Correa-oliveira R, Croese J. Hookworm infection. 2016;.
- 48. Bosch F, Palmeirim MS, Ali SM, Ame SM, Hattendorf J, Keiser J, et al. Diagnosis of soil-transmitted helminths using the kato-katz technique: What is the influence of stirring, storage time and storage temperature on stool sample egg counts? PLoS Negl Trop Dis. 2021;15(1):1–17.