Prevalence and under-detection of gambiense human African trypanosomiasis during mass screening sessions in Uganda and Sudan.


Checchi, F; Cox, AP; Chappuis, F; Priotto, G; Chandramohan, D; Haydon, DT; (2012) Prevalence and under-detection of gambiense human African trypanosomiasis during mass screening sessions in Uganda and Sudan. Parasit Vectors, 5. p. 157. ISSN 1756-3305 DOI: https://doi.org/10.1186/1756-3305-5-157

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Abstract

UNLABELLED: ABSTRACT: BACKGROUND: Active case detection through mass community screening is a major control strategy against human African trypanosomiasis (HAT, sleeping sickness) caused by T. brucei gambiense. However, its impact can be limited by incomplete attendance at screening sessions (screening coverage) and diagnostic inaccuracy. METHODS: We developed a model-based approach to estimate the true prevalence and the fraction of cases detected during mass screening, based on observed prevalence, and adjusting for incomplete screening coverage and inaccuracy of diagnostic algorithms for screening, confirmation and HAT stage classification. We applied the model to data from three Médecins Sans Frontières projects in Uganda (Adjumani, Arua-Yumbe) and Southern Sudan (Kiri). RESULTS: We analysed 604 screening sessions, targeting about 710 000 people. Cases were about twice as likely to attend screening as non-cases, with no apparent difference by stage. Past incidence, population size and repeat screening rounds were strongly associated with observed prevalence. The estimated true prevalence was 0.46% to 0.90% in Kiri depending on the analysis approach, compared to an observed prevalence of 0.45%; 0.59% to 0.87% in Adjumani, compared to 0.92%; and 0.18% to 0.24% in Arua-Yumbe, compared to 0.21%. The true ratio of stage 1 to stage 2 cases was around two-three times higher than that observed, due to stage misclassification. The estimated detected fraction was between 42.2% and 84.0% in Kiri, 52.5% to 79.9% in Adjumani and 59.3% to 88.0% in Arua-Yumbe. CONCLUSIONS: In these well-resourced projects, a moderate to high fraction of cases appeared to be detected through mass screening. True prevalence differed little from observed prevalence for monitoring purposes. We discuss some limitations to our model that illustrate several difficulties of estimating the unseen burden of neglected tropical diseases.

Item Type: Article
Faculty and Department: Faculty of Infectious and Tropical Diseases > Dept of Disease Control
Faculty of Public Health and Policy > Dept of Global Health and Development
Faculty of Epidemiology and Population Health > Dept of Infectious Disease Epidemiology
Research Centre: ECOHOST - The Centre for Health and Social Change
PubMed ID: 22871103
Web of Science ID: 308145500001
URI: http://researchonline.lshtm.ac.uk/id/eprint/210219

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