Mbacké Sembène

Human antibody response to Anopheles gambiae saliva: an immuno-epidemiological biomarker to evaluate the efficacy of insecticide-treated nets in malaria vector control.

For the fight against malaria, the World Health Organization (WHO) has emphasized the need for indicators to evaluate the efficacy of vector-control strategies. This study investigates a potential immunological marker, based on human antibody responses to Anopheles saliva, as a new indicator to evaluate the efficacy of insecticide-treated nets (ITNs). Parasitological, entomological, and immunological assessments were carried out in children and adults from a malaria-endemic region of Angola before and after the introduction of ITNs. Immunoglobulin G (IgG) levels to An. gambiae saliva were positively associated with the intensity of An. gambiae exposure and malaria infection. A significant decrease in the anti-saliva IgG response was observed after the introduction of ITNs, and this was associated with a drop in parasite load. This study represents the first stage in the development of a new indicator to evaluate the efficacy of malaria vector-control strategies, which could apply in other arthropod vector-borne diseases.

Human Antibody Responses to the Anopheles Salivary gSG6-P1 Peptide: A Novel Tool for Evaluating the Efficacy of ITNs in Malaria Vector Control

To optimize malaria control, WHO has prioritised the need for new indicators to evaluate the efficacy of malaria vector control strategies. The gSG6-P1 peptide from gSG6 protein of Anopheles gambiae salivary glands was previously designed as a specific salivary sequence of malaria vector species. It was shown that the quantification of human antibody (Ab) responses to Anopheles salivary proteins in general and especially to the gSG6-P1 peptide was a pertinent biomarker of human exposure to Anopheles. The present objective was to validate this indicator in the evaluation of the efficacy of Insecticide Treated Nets (ITNs). A longitudinal evaluation, including parasitological, entomological and immunological assessments, was conducted on children and adults from a malaria-endemic area before and after the introduction of ITNs. Significant decrease of anti-gSG6-P1 IgG response was observed just after the efficient ITNs use. Interestingly, specific IgG Ab level was especially pertinent to evaluate a short-time period of ITNs efficacy and at individual level. However, specific IgG rose back up within four months as correct ITN use waned. IgG responses to one salivary peptide could constitute a reliable biomarker for the evaluation of ITN efficacy, at short- and long-term use, and provide a valuable tool in malaria vector control based on a real measurement of human-vector contact.

IgG responses to the gSG6-P1 salivary peptide for evaluating human exposure to Anopheles bites in urban areas of Dakar region, Sénégal

BackgroundUrban malaria can be a serious public health problem in Africa. Human-landing catches of mosquitoes, a standard entomological method to assess human exposure to malaria vector bites, can lack sensitivity in areas where exposure is low. A simple and highly sensitive tool could be a complementary indicator for evaluating malaria exposure in such epidemiological contexts. The human antibody response to the specific Anopheles gSG6-P1 salivary peptide have been described as an adequate tool biomarker for a reliable assessment of human exposure level to Anopheles bites. The aim of this study was to use this biomarker to evaluate the human exposure to Anopheles mosquito bites in urban settings of Dakar (Senegal), one of the largest cities in West Africa, where Anopheles biting rates and malaria transmission are supposed to be low.MethodsOne cross-sectional study concerning 1,010 (505 households) children (n = 505) and adults (n = 505) living in 16 districts of downtown Dakar and its suburbs was performed from October to December 2008. The IgG responses to gSG6-P1 peptide have been assessed and compared to entomological data obtained in or near the same district.ResultsConsiderable individual variations in anti-gSG6-P1 IgG levels were observed between and within districts. In spite of this individual heterogeneity, the median level of specific IgG and the percentage of immune responders differed significantly between districts. A positive and significant association was observed between the exposure levels to Anopheles gambiae bites, estimated by classical entomological methods, and the median IgG levels or the percentage of immune responders measuring the contact between human populations and Anopheles mosquitoes. Interestingly, immunological parameters seemed to better discriminate the exposure level to Anopheles bites between different exposure groups of districts.ConclusionsSpecific human IgG responses to gSG6-P1 peptide biomarker represent, at the population and individual levels, a credible new alternative tool to assess accurately the heterogeneity of exposure level to Anopheles bites and malaria risk in low urban transmission areas. The development of such biomarker tool would be particularly relevant for mapping and monitoring malaria risk and for measuring the efficiency of vector control strategies in these specific settings.

Epidemiology of Staphylococcus aureus in pigs and farmers in the largest farm in Dakar, Senegal.

Between December 2009 and November 2011, we collected 57 (12.3%) Staphylococcus aureus isolates from 464 pigs and 16 (30.8%) isolates from 52 farmers in the largest farm in Dakar. Fifty-one isolates (70%) belonged to four major multilocus sequence typing clonal complexes (CCs): CC152 (26.0%), CC15 (19.2%), CC5 (13.7%), and CC97 (10.9%). The CC variability among the pigs was similar to that observed among the farmers. Six isolates that were recovered only among pigs were resistant to methicillin (10.5%). They were assigned to the ST5-staphylococcal cassette chromosome mec type (SCCmec) IV (n = 5) and ST88-SCCmec IV (n = 1) clones. The luk-PV genes encoding Panton-Valentine leukocidin (PVL), present in 43 (58.9%) isolates overall, including all major CCs and the MRSA ST5-SCCmec IV clone, were highly prevalent compared to data from industrialized countries. This finding is of major concern with regard to the potential virulence of these strains.

Evolutionary systematics and biogeography of endemic gerbils (Rodentia, Muridae) from Morocco: an integrative approach

Ndiaye, A., Bâ, K., Aniskin, V., Benazzou, T., Chevret, P., Konečný, A., Sembène, M., Tatard, C., Kergoat, G.J. & Granjon, L. (2011). Evolutionary systematics and biogeography of endemic gerbils (Rodentia, Muridae) from Morocco: an integrative approach. —Zoologica Scripta, 41, 11–28.

Community-acquired diarrhea among children and adults in urban settings in Senegal: clinical, epidemiological and microbiological aspects

BackgroundOnly limited data are available relating to the etiology of diarrhea in children and adults in Senegal. The aim of this prospective study was to describe the epidemiology and etiology of community-acquired diarrheal infections in children and adults living in urban settings.MethodsA prospective study was carried out from March 2009 to December 2010, in the urban region of Dakar, Senegal. Patients with acute diarrhea were enrolled, interviewed to collect their clinical history, and their stools were tested for bacteria, virus and parasites.ResultsA total of 223 patients (including 112 children younger than five years old) with diarrhea were included. At least one enteropathogen was detected in 81% (180/223) of the patients: 29% (64/223) had bacterial infections (mainly diarrheagenic E. coli and Shigella spp), 21% (39/185) viral infections (mainly rotavirus) and 14% (31/223) parasitic infections. Co-infection was identified in 17.8% (32/180) of the patients. Viral infection was significantly more frequent in children under five years old during the dry season. Bacteria and parasites were equally frequent in all age groups. There was a seasonal variation of bacterial infections during the study period, with a higher proportion of infections being bacterial, and due to Salmonella spp. in particular, during the rainy season.ConclusionOur study suggests that in urban settings in Senegal, rotavirus is the principal cause of pediatric diarrhea during the dry season and that the proportion of bacterial infections seems to be higher during the rainy season. Further work is needed to document the burden of diarrheal diseases in sub-Saharan urban communities and to identify risk factors, including those linked to the rapid and unplanned urbanization in Africa.

Genetic differentiation of groundnut seed‐beetle populations in Senegal

Caryedon serratus, the groundnut seed‐beetle, is a major pest of groundnut (Arachis hypogaea), an introduced legume in the subfamily Papilionoideae. Native hosts of C. serratus in Senegal include Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica, all of which belong to the legume subfamily Caesalpinioideae.

Identity of the groundnut and tamarind seed-beetles (Coleoptera: Bruchidae: Pachymerinae), with the restoration of Caryedon gonagra (F.)

Abstract The study of seed-beetles feeding on groundnuts (Arachis hypogaea), tamarind (Tamarindus indica) and other Caesalpinioideae from various areas of the Old World, enables the authors to characterize two different species of Caryedon that are usually confused. C. serratus (Ol.), usually known as the «groundnut seed-beetle», feeds on seeds of tamarind and various wild Caesalpinioideae in the genera Piliostigma, Cassia and Bauhinia. It is present in West and Central Africa. Detailed morphological studies associated with the analysis of part of the Cytochrome B gene show that another species, Caryedon gonagra, infests tamarind and other Caesalpinioideae in Egypt, South Asia, Australia and New Caledonia; this species also feeds in the seeds of a few Mimosoideae in the genera Acacia, Albizia and Dichrostachys. Caryedon gonagra and C. serratus appear as sister species deriving from an ancestor that may have fed on both Mimosoideae and Caesalpinioideae. Contrary to what happens in C. serratus, it seems that C. gonagra does not infest groundnuts under natural conditions. Larval development in groundnuts under laboratory conditions is however possible, as in several other Caryedon species.

Phylogenetic information reveals the peculiarity of Caryedon serratus (Coleoptera, Chrysomelidae, Bruchinae) feeding on Cassia sieberiana DC (Caesalpinioideae)

Studies over the past 20 years on natural populations indicated that sympatric speciation may be far more common and widespread among plants and animals than previously thought. By using molecular phylogenetics (on a combined data set of two genes), the relationships between Caryedon serratus native forms and forms feeding on groundnut was investigated. The specific objectives were to clarify the taxonomic status of C. serratus feeding on Cassia sieberiana DC. Morphological analysis was conducted, using parts of the adult specimens which were dry-mounted for the studies. Morphological study comprised extraction of the genitalia, which were cleared and mounted in Canada balsam following standard procedures. Results showed a strong differentiation of insects from different hosts’ trees, with specimens from C. sieberiana possibly representing a sibling species.

Insecticidal activity of Boscia senegalensis (Pers.) Lam ex Poir. on Caryedon serratus (Ol.) pest of stored groundnuts

Institut de Technologie Alimentaire, Hann-Dakar, BP 2765, Senegal. Centre Regional de Recherche en Ecotoxicologie et Securite Environnementale (CERES/Locustox), km 15 Route de Rufisque, BP 3300 Dakar, Senegal. CIP (International Potato Center) – BP 08 0932Cotonou, Benin. Departement de Biologie Animale, Faculte des Sciences de Dakar, UCAD, BP 5005, Dakar, Senegal. Universite de Liege, Gembloux Agro-Bio Tech, Unite de Chimie Generale et Organique, 2 Passage des Deportes -5030 Gembloux, Belgique. Universite de Liege, Gembloux Agro-Bio Tech, Unite de Chimie Analytique, 2, Passage des Deportes -5030 Gembloux, Belgique.