Pilot Assessment of Soil-Transmitted Helminthiasis in the Context of Transmission Assessment Surveys for Lymphatic Filariasis in Benin and Tonga

<div><p>Background</p><p>Mass drug administration (MDA) for lymphatic filariasis (LF) programs has delivered more than 2 billion treatments of albendazole, in combination with either ivermectin or diethylcarbamazine, to communities co-endemic for soil-transmitted helminthiasis (STH), reducing the prevalence of both diseases. A transmission assessment survey (TAS) is recommended to determine if MDA for LF can be stopped within an evaluation unit (EU) after at least five rounds of annual treatment. The TAS also provides an opportunity to simultaneously assess the impact of these MDAs on STH and to determine the frequency of school-based MDA for STH after community-wide MDA is no longer needed for LF.</p><p>Methodology/Principal Findings</p><p>Pilot studies conducted in Benin and Tonga assessed the feasibility of a coordinated approach. Of the schools (clusters) selected for a TAS in each EU, a subset of 5 schools per STH ecological zone was randomly selected, according to World Health Organization (WHO) guidelines, for the coordinated survey. In Benin, 519 children were sampled in 5 schools and 22 (4.2%) had STH infection (<i>A. lumbricoides</i>, <i>T. trichiura</i>, or hookworm) detected using the Kato-Katz method. All infections were classified as light intensity under WHO criteria. In Tonga, 10 schools were chosen for the coordinated TAS and STH survey covering two ecological zones; 32 of 232 (13.8%) children were infected in Tongatapu and 82 of 320 (25.6%) in Vava'u and Ha'apai. All infections were light-intensity with the exception of one with moderate-intensity <i>T. trichiura</i>.</p><p>Conclusions</p><p>Synchronous assessment of STH with TAS is feasible and provides a well-timed evaluation of infection prevalence to guide ongoing treatment decisions at a time when MDA for LF may be stopped. The coordinated field experiences in both countries also suggest potential time and cost savings. Refinement of a coordinated TAS and STH sampling methodology should be pursued, along with further validation of alternative quantitative diagnostic tests for STH that can be used with preserved stool specimens.</p></div

Benin STH infection by age group.

<p>Benin STH infection by age group.</p

Benin TAS and STH survey results.

1<p>Mean epg was only calculated for positive cases.</p

Schistosomiasis and Soil Transmitted Helminths Distribution in Benin: A Baseline Prevalence Survey in 30 Districts

<div><p>In 2013, Benin developed strategies to control neglected tropical diseases and one of the first step was the disease mapping of the entire country in order to identify endemic districts of schistosomiasis and soil transmitted helminths (STH). This study was carried out in 30 of the 77 districts of Benin. Of these 30 districts 22 were previously treated for Lymphatic Filariasis (LF) using the Ivermectin and Albendazole combination. In each district, five schools were selected and 50 children aged 8 to 14 years were sampled in each school, making a total of 250 children sampled in the district. The schools were selected mainly according to their proximity to lakes or any bodies of water that were likely to have been used by the children. Samples of faeces and urine were collected from each pupil. Urinary schistosomiasis was identified using the urine filtration technique while STH and intestinal schistosomiasis were identified through the Kato Katz method. Overall a total of 7500 pupils were surveyed across 150 schools with a gender ratio of 1:1. Hookworm was identified in all 30 districts with a prevalence ranging from 1.2% (95%CI: 0.0–2.5) to 60% (95%CI: 53.9–66.1). <i>Ascaris lumbricoides</i> was detected in 19 districts with a prevalence rate between 1% (95%CI: 0.0–2.2) and 39% (95%CI: 32.9–45.0). In addition to these common STH, <i>Trichuris trichiura</i>, <i>Enterobius vermicularis</i> and <i>Strongyloides stercoralis</i> were found at low prevalence. Only 16 districts were endemic to <i>Schistosoma mansoni</i>, while 29 districts were endemic to <i>S</i>. <i>haematobium</i>. The <i>S</i>. <i>haematobium</i> prevalence ranged from 0.8% (95% CI: 0.0–1.9) to 56% (95% CI: 50.2–62.5) while the prevalence of <i>S</i>. <i>mansoni</i> varied from 0.4% (95%CI: 0.0–1.2) to 46% (95% CI: 39.8–52.2). The 22 districts, where LF was successfully eliminated, still require mass drug administration (MDA) of albendazole indicating that school-based MDA would be needed even after LF elimination in districts co-endemic to LF and STH in Benin.</p></div

Sampling strategy for coordinated TAS and STH surveys.

1<p>5 schools per ecological zone; all schools randomly selected from TAS sample except two schools in Tonga that were included in 2001–2002 STH survey.</p

Comparison of TAS and STH survey criteria.

1<p>World Health Organization (2011) Global Programme to Eliminate Lymphatic Filariasis: Monitoring and epidemiological assessment of mass drug administration: a manual for national elimination programs. Geneva.</p>2<p>World Health Organization (2011) Helminth control in school-age children: a guide for managers of control programmes – 2nd ed. Geneva.</p>3<p>Lot quality assurance sampling.</p>4<p>For <i>W. bancrofti</i>.</p

Intensity of urinary and intestinal schistosomiasis infection in districts surveyed.

<p>N: Number of positive samples out the total (250) examined in each commune. For <i>S</i>. <i>haematobium</i> intensity Light: 1–50 eggs/10ml of urine; High: ≥ 50 eggs/10ml of urine For <i>S</i>. <i>mansoni</i> intensity Light: 1-99EPG; Moderate: 100–399 EPG; High: ≥ 400EPG.</p

Comparison of the average prevalence of Hookworm in each department.

<p>On the chart, the department sharing similar letter are not significantly different. Those sharing different letters indicate a significant difference [p<0.0001]</p

Comparison of the prevalence of the most common STH (Hookworm) to <i>S</i>.<i>haematobium</i>.

<p><b>X2: Chi-square value of comparison of Hookworm and S. haematobium prevalence within each district. p-value: p value of comparison of Hookworm and S. haematobium prevalence within each district.</b> In each column, the letter “a”, “b” or “c” indicates that the prevalence sharing similar letter are not significantly different while those sharing different letters are significantly different.</p

Comparison of the average prevalence of <i>S</i>. <i>mansoni</i> in each department.

<p>Comparison of the average prevalence of <i>S</i>. <i>mansoni</i> in each department.</p