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Spatio-temporal dynamics of asymptomatic malaria : bridging the gap between annual malaria resurgences in a Sahelian environment

Drissa Coulibaly 1 Mark Travassos 1 Youssouf Tolo 1 Matthew Laurens 1 Abdoulaye Koné 2 Karim Traore 3 Mody Sissoko 4 Amadou Niangaly 1 Issa Diarra 1 Modibo Daou Boureima Guindo Stanislas Rebaudet 5, 6 Bourema Kouriba 7 Nadine Dessay 8 Renaud Piarroux 6 Christopher Plowe Ogobara Doumbo 9, 10 Mahamadou Thera 2 Jean Gaudart 4, 10
1 Département d'Epidémiologie des Affections parasitaires, Malaria Research and training center Université de Bamako, Mali
2 DEAP - Département d'épidémiologie des affections parasitaires
3 IMETI - Institut des Maladies Emergentes et des Thérapies Innovantes
4 AMU - Aix Marseille Université
5 APHM - Assistance Publique - Hôpitaux de Marseille
6 iPLESP - Institut Pierre Louis d'Epidémiologie et de Santé Publique
7 MRTC - Malaria Research and Training Center
8 UMR 228 Espace-Dev, Espace pour le développement
9 Malaria Research and Training Centre
10 SESSTIM - U912 INSERM - Aix Marseille Univ - IRD - Sciences Economiques et Sociales de la Santé & Traitement de l'Information Médicale
Abstract : These authors contributed equally to this work. Abstract. In areas of seasonal malaria transmission, the incidence rate of malaria infection is presumed to be near zero at the end of the dry season. Asymptomatic individuals may constitute a major parasite reservoir during this time. We conducted a longitudinal analysis of the spatio-temporal distribution of clinical malaria and asymptomatic parasitemia over time in a Malian town to highlight these malaria transmission dynamics. For a cohort of 300 rural children followed over 2009–2014, periodicity and phase shift between malaria and rainfall were determined by spectral analysis. Spatial risk clusters of clinical episodes or carriage were identified. A nested-case-control study was conducted to assess the parasite carriage factors. Malaria infection persisted over the entire year with seasonal peaks. High transmission periods began 2–3 months after the rains began. A cluster with a low risk of clinical malaria in the town center persisted in high and low transmission periods. Throughout 2009–2014, cluster locations did not vary from year to year. Asymptomatic and gametocyte carriage were persistent, even during low transmission periods. For high transmission periods, the ratio of asymptomatic to clinical cases was approximately 0.5, but was five times higher during low transmission periods. Clinical episodes at previous high transmission periods were a protective factor for asymptomatic carriage, but carrying parasites without symptoms at a previous high transmission period was a risk factor for asymptomatic carriage. Stable malaria transmission was associated with sustained asymptomatic carriage during dry seasons. Control strategies should target persistent low-level parasitemia clusters to interrupt transmission.
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IRD | CNRS | UPMC | CEA | UNIV-AMU | IPLESP | ESPACE-DEV | AGROPOLIS | GUYANE | MIPS | UNIV-MONTPELLIER | JACOB | CEA-DRF | UNIV-AG | CEA-UPSAY | U1252 | SORBONNE-UNIVERSITE | SU-MEDECINE | UNIV-AVIGNON | UNIV-PERP | AFRIQ

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Drissa Coulibaly, Mark Travassos, Youssouf Tolo, Matthew Laurens, Abdoulaye Koné, et al.. Spatio-temporal dynamics of asymptomatic malaria : bridging the gap between annual malaria resurgences in a Sahelian environment. American Journal of Tropical Medicine and Hygiene, American Society of Tropical Medicine and Hygiene, 2017, 20 p. ⟨10.4269/ajtmh.17-0074⟩. ⟨ird-01630569⟩

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