Integrated mapping of lymphatic filariasis and podoconiosis: lessons learnt from Ethiopia

BACKGROUND The World Health Organization (WHO), international donors and partners have emphasized the importance of integrated control of neglected tropical diseases (NTDs). Integrated mapping of NTDs is a first step for integrated planning of programmes, proper resource allocation and monitoring progress of control. Integrated mapping has several advantages over disease specific mapping by reducing costs and enabling co-endemic areas to be more precisely identified. We designed and conducted integrated mapping of lymphatic filariasis (LF) and podoconiosis in Ethiopia; here we present the methods, challenges and lessons learnt. METHODS Integrated mapping of 1315 communities across Ethiopia was accomplished within three months. Within these communities, 129,959 individuals provided blood samples that were tested for circulating Wuchereria bancrofti antigen using immunochromatographic card tests (ICT). Wb123 antibody tests were used to further establish exposure to LF in areas where at least one ICT positive individual was detected. A clinical algorithm was used to reliably diagnose podoconiosis by excluding other potential causes of lymphoedema of the lower limb. RESULTS A total of 8110 individuals with leg swelling were interviewed and underwent physical examination. Smartphones linked to a central database were used to collect data, which facilitated real-time data entry and reduced costs compared to traditional paper-based data collection approach; their inbuilt Geographic Positioning System (GPS) function enabled simultaneous capture of geographical coordinates. The integrated approach led to efficient use of resources and rapid mapping of an enormous geographical area and was well received by survey staff and collaborators. Mobile based technology can be used for such large scale studies in resource constrained settings such as Ethiopia, with minimal challenges. CONCLUSIONS This was the first integrated mapping of podoconiosis and LF globally. Integrated mapping of podoconiosis and LF is feasible and, if properly planned, can be quickly achieved at nationwide scale

Epidemiology and individual, household and geographical risk factors of podoconiosis in ethiopia: results from the first nationwide mapping

Although podoconiosis is one of the major causes of tropical lymphoedema and is endemic in Ethiopia its epidemiology and risk factors are poorly understood. Individual-level data for 129,959 individuals from 1,315 communities in 659 woreda (districts) were collected for a nationwide integrated survey of lymphatic filariasis and podoconiosis. Blood samples were tested for circulating Wuchereria bancrofti antigen using immunochromatographic card tests. A clinical algorithm was used to reach a diagnosis of podoconiosis by excluding other potential causes of lymphoedema of the lower limb. Bayesian multilevel models were used to identify individual and environmental risk factors. Overall, 8,110 of 129,959 (6.2%, 95% confidence interval [CI] 6.1-6.4%) surveyed individuals were identified with lymphoedema of the lower limb, of whom 5,253 (4.0%, 95% CI 3.9-4.1%) were confirmed to be podoconiosis cases. In multivariable analysis, being female, older, unmarried, washing the feet less frequently than daily, and being semiskilled or unemployed were significantly associated with increased risk of podoconiosis. Attending formal education and living in a house with a covered floor were associated with decreased risk of podoconiosis. Podoconiosis exhibits marked geographical variation across Ethiopia, with variation in risk associated with variation in rainfall, enhanced vegetation index, and altitude

Mapping and modelling the geographical distribution and environmental limits of podoconiosis in Ethiopia

BACKGROUND Ethiopia is assumed to have the highest burden of podoconiosis globally, but the geographical distribution and environmental limits and correlates are yet to be fully investigated. In this paper we use data from a nationwide survey to address these issues. METHODOLOGY Our analyses are based on data arising from the integrated mapping of podoconiosis and lymphatic filariasis (LF) conducted in 2013, supplemented by data from an earlier mapping of LF in western Ethiopia in 2008-2010. The integrated mapping used woreda (district) health offices' reports of podoconiosis and LF to guide selection of survey sites. A suite of environmental and climatic data and boosted regression tree (BRT) modelling was used to investigate environmental limits and predict the probability of podoconiosis occurrence. PRINCIPAL FINDINGS Data were available for 141,238 individuals from 1,442 communities in 775 districts from all nine regional states and two city administrations of Ethiopia. In 41.9% of surveyed districts no cases of podoconiosis were identified, with all districts in Affar, Dire Dawa, Somali and Gambella regional states lacking the disease. The disease was most common, with lymphoedema positivity rate exceeding 5%, in the central highlands of Ethiopia, in Amhara, Oromia and Southern Nations, Nationalities and Peoples regional states. BRT modelling indicated that the probability of podoconiosis occurrence increased with increasing altitude, precipitation and silt fraction of soil and decreased with population density and clay content. Based on the BRT model, we estimate that in 2010, 34.9 (95% confidence interval [CI]: 20.2-51.7) million people (i.e. 43.8%; 95% CI: 25.3-64.8% of Ethiopia's national population) lived in areas environmentally suitable for the occurrence of podoconiosis. CONCLUSIONS Podoconiosis is more widespread in Ethiopia than previously estimated, but occurs in distinct geographical regions that are tied to identifiable environmental factors. The resultant maps can be used to guide programme planning and implementation and estimate disease burden in Ethiopia. This work provides a framework with which the geographical limits of podoconiosis could be delineated at a continental scale

Additional file 2 of Temporal dynamics of Plasmodium falciparum population in Metehara, east-central Ethiopia

Additional file 2. Primers used for msp2 genotyping

Additional file 1 of Temporal dynamics of Plasmodium falciparum population in Metehara, east-central Ethiopia

Additional file 1. Primers used for msp1 genotyping

Additional file 3 of Temporal dynamics of Plasmodium falciparum population in Metehara, east-central Ethiopia

Additional file 3. Primers used for glurp genotyping

School Water, Sanitation, and Hygiene, Soil-Transmitted Helminths, and Schistosomes: National Mapping in Ethiopia

<div><p>Background</p><p>It is thought that improving water, sanitation, and hygiene (WASH) might reduce the transmission of schistosomes and soil-transmitted helminths, owing to their life cycles. However, few large-scale studies have yet assessed the real extent of associations between WASH and these parasites.</p><p>Methodology/Principal Findings</p><p>In the 2013–2014 Ethiopian national mapping of infections with these parasites, school WASH was assessed alongside infection intensity in children, mostly between 10 and 15 years of age. Scores were constructed reflecting exposure to schistosomes arising from water collection for schools, from freshwater sources, and the adequacy of school sanitation and hygiene facilities. Kendall’s <i>τ</i>_<i>b</i> was used to test the WASH scores against the school-level arithmetic mean intensity of infection with each parasite, in schools with at least one child positive for the parasite in question.</p><p>WASH and parasitology data were available for 1,645 schools. More frequent collection of water for schools, from open freshwater sources was associated with statistically significantly higher <i>Schistosoma mansoni</i> infection intensity (Kendall’s <i>τ</i>_<i>b</i> = 0.097, 95% confidence interval, CI: 0.011 to 0.18), better sanitation was associated with significantly lower <i>Ascaris lumbricoides</i> intensity (Kendall’s <i>τ</i>_<i>b</i> = -0.067, 95% CI: -0.11 to -0.023) and borderline significant lower hookworm intensity (Kendall’s <i>τ</i>_<i>b</i> = -0.039, 95% CI: -0.090 to 0.012, <i>P</i> = 0.067), and better hygiene was associated with significantly lower hookworm intensity (Kendall’s <i>τ</i>_<i>b</i> = -0.076, 95% CI: -0.13 to -0.020). However, no significant differences were observed when comparing sanitation and infection with <i>S</i>. <i>mansoni</i> or <i>Trichuris trichiura</i>, or hygiene and infection with <i>A</i>. <i>lumbricoides</i> or <i>T</i>. <i>trichiura</i>.</p><p>Conclusions/Significance</p><p>Improving school WASH may reduce transmission of these parasites. However, different forms of WASH appear to have different effects on infection with the various parasites, with our analysis finding the strongest associations between water and <i>S</i>. <i>mansoni</i>, sanitation and <i>A</i>. <i>lumbricoides</i>, and hygiene and hookworm.</p></div

Summary of aspects of latrine conditions used in the calculation of the sanitation and hygiene scores.

<p>Summary of aspects of latrine conditions used in the calculation of the sanitation and hygiene scores.</p

School water scores and arithmetic mean intensities of <i>S</i>. <i>mansoni</i> infection.

<p>Kendall’s <i>τ</i>_<i>b</i> statistics, the equation of the least-squares line of best fit, and the number of included schools, are presented in the upper-right corner.</p

Flow diagram demonstrating the calculation of the sanitation score.

<p>Flow diagram demonstrating the calculation of the sanitation score.</p