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Enquête d’évaluation de la transmission de la filariose lymphatique en milieu scolaire, 3 ans après l’arrêt du traitement de masse à l’albendazole et à l’ivermectine dans les 7 districts endémiques du Togo

Lymphatic filariasis transmission assessment survey in schools three years after stopping mass drug treatment with albendazole and ivermectine in the 7 endemic districts in Togo

Bulletin de la Société de pathologie exotique

Résumé

Une enquête a été réalisée en 2012 en vue de vérifier le niveau de la transmission de Wuchereria bancrofti 3 ans après l’arrêt du traitement de masse dans les 7 districts endémiques du Togo. La méthode utilisée est celle recommandée par l’Organisation Mondiale de la Santé. Les 7 districts ont été regroupés en 4 unités d’évaluation (UE). La recherche de l’antigène filarien par la carte immunochromatographique ICT a été faite chez des enfants âgés de 6 et 7 ans sélectionnés en milieu scolaire selon la technique d’échantillonnage en grappes. Une UE est qualifiée avoir passé le test avec succès lorsque le nombre de cas positifs retrouvés est inférieur au nombre critique qui est de 18 pour chacune des 4 UE. Sur les 1 706 enfants enquêtés dans l’UE Tone-Kpendjal, les 1 549 dans l’UE Binah-Doufelgou, les 1 550 dans l’UE Kozah et les 1 575 dans l’UE Amou-Haho, 8 (0,46 %), 1 (0,08 %), 0 (0,00 %) et 4 (0,25 %) cas respectivement ont été retrouvés positifs correspondant à des taux très en dessous du seuil-critique. De plus, l’ensemble de ces 13 cas positifs à l’ICT se sont révélés négatifs aux examens supplémentaires (recherche d’une microfilarémie nocturne et d’antigènes circulants par l’ELISA-Og4C3). Le risque de recrudescence de l’infection est donc resté faible dans les 7 districts, 3 ans après l’arrêt des traitements.

Abstract

The aim of this study is to verify the level of transmission of lymphatic filariasis three years after stopping mass drug treatment in the 7 endemic districts in Togo. The survey was conducted in 2012 in Togo’s 7 endemic districts grouped into four evaluation units (EU) using theWHO-recommended transmission assessment survey (TAS) protocol. Children aged 6–7 years were screened for Wuchereria bancofti antigen using the immunochromatographic card (ICT) method. A cluster sampling method was used to select eligible children in schools as the net primary-school enrolment ratio is greater than or equal to 75% in each of the four EUs. The number of children and schools to be selected in each EU, the randomization list for the selection of these children and the critical cut-off number of positive cases not to exceed were automatically generated using the Survey Sample Builder (SSB) tool, (NTD Support Center, Atlanta, Ga, USA). For confirmation, positive cases were subsequently tested for microfilaremia using nocturnal thick blood smear and for filarial antigen using Og4C3 antigen ELISA (TropBio ELISA Kit®, Townsville, Queensland, Australia). An EU is considered to have passed the test successfully (it is assumed that transmission can no longer be sustained), when the number of positive cases is below the critical cut-off number set by the SSB, which is roughly equivalent to 2% prevalence. Of the 1 706 children surveyed in Kpendjal-Tone’s EU, 1 549 in Binah-Doufelgou’s EU, 1 550 in Kozah’s EU and the 1 575 in Amou-Haho’s EU, 8 (0.46%), 1 (0.08%), 0 (0.00%) and 4 (0.25%) ICT positive cases respectively were detected. The number of positive ICT tests was well below 18, the criticalcut number for each of the 4 EUs. All 13 ICT positive cases tested negative for nocturnal microfilaremia and Og4C3 ELISA. We conclude that all four EU passed the TAS with success, and the transmission of Wuchereria bancrofti is no longer likely to be sustained in the 7 endemic districts in Togo 3 years after stopping the MDA. A new TAS will be carried out in 2015, after which, if the results are still good, the country will submit a dossier to WHO for verification of the elimination of lymphatic filariasis.

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Dorkenoo, A.M., Sodahlon, Y.K., Bronzan, R.N. et al. Enquête d’évaluation de la transmission de la filariose lymphatique en milieu scolaire, 3 ans après l’arrêt du traitement de masse à l’albendazole et à l’ivermectine dans les 7 districts endémiques du Togo. Bull. Soc. Pathol. Exot. 108, 181–187 (2015). https://doi.org/10.1007/s13149-014-0408-z

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  • DOI: https://doi.org/10.1007/s13149-014-0408-z

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