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Malaria in mangrove areas (Saloum, Senegal) Volume 5, issue 2, Mars-Avril 2006

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Authors
Institut de recherche pour le développement (IRD), Unité de recherche 077 « Paludologie afrotropicale », Centre IRD de Hann, BP 1386, CP 18524 Dakar Sénégal, Département de biologie animale, Faculté des sciences et techniques, Université C.A. Diop (Ucad), BP 5005, Dakar Sénégal, Institut de recherche pour le développement (IRD), Unité de recherche 178 « Conditions et territoires d’émergences des maladies », Centre IRD de Hann, BP 1386, CP 18524 Dakar Sénégal, Service de parasitologie, Faculté de médecine et de pharmacie, Université C.A. Diop (Ucad), BP 5005, Dakar Sénégal, Institut de recherche pour le développement (IRD), Unité de recherche 016 « Caractérisation et contrôle des populations de vecteurs », Laboratoire des insectes nuisibles (LIN), BP 64501, 34394 Montpellier cedex 5 France, Service national de lutte antiparasitaire (SLAP), BP - SLAP, Thiès Sénégal

This study of malaria biodiversity in Senegal used an entomological approach that combined parasite surveys and clinical investigations in the mangrove area of the Saloum delta from 1996 to 1998. The parasitologic studies took place in two of the six villages in the coastal area of Palmarin (Djifère and Diakhanor) during three distinct periods: at the end of the dry season, in the middle of the rainy season, and at the end of the rainy season. The clinical investigations at the Palmarin health station took place from July 1996 through February 1998. A malaria attack was defined as the presence of malaria symptoms (including fever, headaches, sweating, and shivering) associated with plasmodic parasitemia > 3,000 trophozoites/µL of blood. All the positive thick smears were infected with Plasmodium falciparum, one also with P. falciparum, and none with P. ovale. The average plasmodic index (5.6%) classifies the delta of Saloum as a hypoendemic area. The average parasite load was estimated at 2,239 trophozoites (95% CI: 1,660-3,020) of P. falciparum per microliter of blood, and 86.9% of patients with symptoms of a malaria attack were febrile. Malaria attacks accounted for 1.9% of the total consultations, 12.2% of the presumed malaria cases, and 14.0% of the febrile subjects. The finding that malaria attacks affected all age groups confirms the weakness of anti-malaria immunity among the population of the Saloum delta. Malaria cases were more frequent at the end of the rainy season and the beginning of the dry season, periods when parasite loads were highest. In this area, which is increasingly attractive to tourists and has a quite superficial fresh water table, man-made environmental changes favor mosquito breeding sites that promote the development of An. arabiensis and An. gambiae spp, both known to be major malaria vectors. In view of the population’s weak anti-malaria immunity, this situation may increase malaria transmission and could be followed by epidemics. It is therefore important to set up a functional system of epidemiological monitoring to detect any malaria outbreaks.