Precision and geographical prevalence mapping of schistosomiasis and soil-transmitted helminthiasis among school-aged children in selected districts of north-western Tanzania

Abstract

Background The identification and mapping of at-risk populations at a lower administrative level than the district are prerequisites for the planning, resource allocation and design of impactful control intervention measures. Thus, the objective of the current study was to conduct sub-district precision mapping of soil-transmitted helminthiasis (STH) and schistosomiasis in 29 districts of north-western Tanzania using the current recommended World Health Organization criteria. Methods A cross-sectional survey was conducted in 145 schools between March and May 2021. A urine filtration technique was used for the quantification of Schistosoma haematobium eggs, whereas quantification of Schistosoma mansoni and STH eggs was done using the Kato–Katz technique. Microhaematuria was examined using a urine dipstick. Results The overall prevalences of any STH and schistosome infections were 9.3% [95% confidence interval (95%CI) 8.6–9.9] and 14.6% (95%CI 13.9–15.4), respectively. The overall prevalence of S. mansoni was 8.7% (95%CI 8.1–9.3), and 36.4%, 41.6%, and 21.9% of the children had low, moderate, and heavy infections, respectively. The overall prevalence of S. haematobium was 6.1% (95%CI 5.5–6.5), and 71.7% and 28.3% of the infected children had light and heavy intensity infections, respectively. The prevalence of microhaematuria was 7.3% (95%CI 6.7–7.8), with males having the highest prevalence (8.4%, P < 0.001). The prevalences of Trichuris trichiura, Ascaris lumbricoides and hookworm were, respectively, 1.3% (95%CI 0.1–1.5), 2.9% (95%CI 2.5–3.3) and 6.2% (95%CI 5.7–6.7). Most of the children infected with STH had light to moderate intensities of infection. The overall prevalence of co-infection with STH and schistosomiasis was 19.1%. The prevalence of schistosomiasis (P < 00.1) and STH (P < 0.001) varied significantly between schools and sub-districts. Schistosoma mansoni and S. haematobium were observed in 60 and 71 schools, respectively, whereas any STH was observed in 49 schools. In schools where schistosomiasis was observed, prevalence was < 10% in 90.8% of them, and ranged from ≥ 10% to < 50% in the other 9.2%. In schools where any STH was observed, the prevalence was < 10% in 87.7% of them. Conclusions The data reported here show that schistosomiasis and STH are widely distributed around Lake Victoria. In most of the schools where schistosomiasis and STH occurred the transmission thresholds were low. These data are important and need to be taken into consideration when decisions are made on the implementation of the next round of mass chemotherapies for schistosomiasis and STH in Tanzania. Graphical Abstract

High Specificity but Low Sensitivity of Lab-on-a-Disk Technique in Detecting Soil-Transmitted Helminth Eggs among Pre- and School-Aged Children in North-Western Tanzania

“…The district is highly endemic for STH infections especially in high altitudes areas. A school-based survey reported a hookworm prevalence ranging from 10–59.5%, that of A. lumbricoides from 10–16.7% and of T. trichiura 7% [ 10 ]. Annual MDA using ALB against STH infections is organized within the school environment and focuses on school-aged children.…”

“…Annual MDA using ALB against STH infections is organized within the school environment and focuses on school-aged children. The study involved pre-school and school-aged children purposively selected based on precision mapping results [ 10 ], and schools which had a high prevalence of STH infections. The selected schools were Bugasha, Kimbugu, Mazinga, Rwakahoza and Rwazi from the Muleba district.…”

“…A cross-sectional study was implemented among pre-school and school-aged children from five purposively selected primary schools in Muleba district. The schools were selected based on the findings of previous studies, which indicated the schools were highly endemic for STH infections [ 10 , 17 ]. Children were included if they were in the age range of 4–17 years (the age group with high prevalence of STH), enrolled at the selected primary schools, with no history of using ALB in the past 6 months based on the school deworming report, either male or female, and if they had submitted a signed informed consent from their parents/guardians.…”

“…Following repeated mass preventive chemotherapies in north-western Tanzania, the epidemiology of STH has changed, with the majority of infected individuals carrying low to moderate infection intensities [ 7 , 8 , 9 , 10 ]. The observed changes in intensities of infection present a new challenge to currently used parasitological techniques, especially the Kato–Katz technique, which is used to monitor drug efficacy and the impact of preventive chemotherapy.…”

Where will pediatric praziquantel be needed in Tanzania? Geographical variation in prevalence, and risk factors of Schistosoma mansoni in pre-school aged children in southern and north-western Tanzania

“…Schistosoma mansoni which cause intestinal schistosomiasis is endemic in Tanzania, with its prevalence varies from one geographical setting to another ( Mazigo et al, 2012 ; Mazigo et al, 2022 ). The south-eastern and south-western sides of the Lake Victoria has been widely studied and evidence indicate that S. mansoni infection is widely distributed in these areas ( Mazigo et al, 2012 ; Mazigo et al, 2022 ; Mueller et al, 2019 ; Mugono et al, 2014 ). There is limited information about the geographical distribution of S. mansoni infection in southern Tanzania, especially along the large water bodies.…”