Influence de la litière foliaire de cinq espèces végétales tropicales sur la diversité floristique des herbacées dans la zone du Ferlo (Senegal)

L’objectif de cette étude a été d’évaluer l’effet de la présence de cinq plantes ligneuses: Balanites aegyptiaca (L.) Del., Acacia tortilis subsp. raddiana (Savi) Brenan, Acacia senegal (L.) Willd, Boscia senegalensis (Pers.) Lam. ex Poir. et Sclerocarya birrea (A. Rich.) Hochst. sur la diversité spécifique de la végétation herbacée dans le Ferlo, au Nord-Sénégal. Il a été procédé à un inventaire des espèces herbacées sous couvert et hors couvert des plantes ligneuses. Ensuite, une analyse floristique qualitative (familles, genres et espèces) a été réalisée à partir de la liste floristique des différents inventaires. Cette analyse a été couplée à une approche quantitative en utilisant le coefficient de similitude de Sørensen qui a servi à définir l’indice de diversité beta. Les résultats de l’inventaire floristique ont permis de dénombrer 28 espèces herbacées réparties dans 25 genres et 15 familles. Les plantes ligneuses comme B. senegalensis, B. aegyptiaca et S. birrea possèdent la flore la plus riche avec 18 espèces chacune, alors que A. tortilis et A. senegal ont respectivement 12 et 9 espèces. Le témoin est le moins diversifié avec 6 espèces herbacées. Parmi les herbacées, Aristida mutabilis est la plus fréquente contrairement à Achyranthes aspera, Aristida adsentionis, Chloris barbata, Cleome  viscosa, Cyperus esculentus, Datura metel, Eragrostis pilosa et Indigofera hirsuta qui sont les espèces les moins fréquentes. Les résultats de l’AFC ont montré quatre groupements végétaux. Un premier groupement qui regroupe B. senegalensis, A. raddiana et le témoin, un groupement à B. aegyptiaca, un groupement à A. senegal et enfin un groupement à S. birrea. Cette étude a permis de mettre en évidence la valeur de la présence de l’arbre dans un système de production fortement dégradé.Mots clés: Sénégal, Ferlo, interaction arbre - herbe, AFC, diversité floristique

Experimental study of slow sand filtration for the treatment of various wastewaters in tropical environment

Wastewater treatment by slow sand filtration is a biological process which consists in filtering wastewater through a porous media. The objective of this study was to evaluate the performances of this biotechnology under tropical climate. Three sand filters were monitored at ONAS (Cambérène wastewater treatment plant in Dakar, Senegal). The filters were built with local materials, and were constituted with a feeding tank of approximately 180 litters, a column (two meters high and 30-25 cm diameter). The filters were filled with sand (75 cm), gravel (25 cm) and wastewater (90 cm). The results showed that with sand of d10 equal to 0.58 mm and flow rate of 0.05 m/h, the filtration cycle was relatively long for the first run with pretreated wastewater. At the level of the primary settling tank, with flow a rate of 0.08 m/h, the removal rates were about 12.75%, 16.31%, 12.92%, 5.45%, 7.09% and 10.50% for TSS, COD, BOD5, nitrogen phosphorus and faecal coliforms respectively. At the level of the clarifier, with a filtration of 0.15 m/h, the removals were 1.4% for TSS, 1.84% for COD, 1.09% for BOD5 11.38% for nitrogen, 5.18% for phosphorus and 1.74% of faecal coliforms.Keywords: Flow rate; filtration cycle, removal; sand filtration; tropical climate, wastewater

Caractérisation agropédologique des sols de mboltime dans la zone des niayes (Sénégal)

L'objectif de cette étude était de faire une évaluation de la fertilité physico-chimique de différents sols du village de Mboltime et de déterminer les similarités relatives. Les horizons de cinq fosses pédologiques (P1 , P2, P3, P4 et P5) ouvertes dans les zones dunaires et inter-dunaires ont servi à cet effet. Les résultats obtenus ont montré que les horizons de surface sont sableux à sablo-limoneux avec des pH et conductivité électrique variant selon les profils et les horizons. Seul le profil P4 a montré des sols acides et salés au niveau des horizons P4H1, P4H3 et P4H5. Les autres profils ont montré des sols neutres à légèrement alcalins et non salins. Les teneurs en matière organique et azote total ont été assez faibles dans les profils 1, 2, 3 et 5, et moyens dans le profil 4 avec un rapport C/N variant de 2,72 à 16,50. Les teneurs en Ca2+, Mg2+, Na+ et K+ varient suivant le C et N. Le cation le plus abondant dans les sols a été le Ca2+; suivi du Mg2+ et du Na+ alors que K+ a été le cation le moins abondant. L'analyse factorielle des correspondances (AFC) a permis de mettre en évidence deux groupes de sols en fonction de la salinité et de l'acidité. Un groupe I constitué de sols très salins et un groupe II constitué de sols non salins. Cette étude a mis en évidence deux contraintes majeures à la production végétale dans le village de Mboltime que sont la salinité et l'acidité des sols.Mots clés : Sol, Profil pédologique, Niayes, salinite ; Sénégal AGROPEDOLOGICAL CARACTERIZATION OF MBOLTIME SOILS IN NIAYES AREA (SENEGAL)The objective of this study was to evaluate physico - chemical properties of different soils from Mboltime village and relevant similarities. Horizons of five soil profiles (P1, P2, P3, P4 and P5) in the dune and inter-dune areaswere used for that purpose. The results showed variance in topsoil contents of sand with silt- loam, pH and electric conductivity according to the  profiles. Only the P4 profile presents acid and salty soil to the level asof horizons P4H1, P4H3 and P4H5. The other profiles presented neutral to slightly alkaline soil pH with limited salinity. The soil contents of organic matter, and total nitrogen were rather weak in the profiles 1, 2, 3 and 5, and moderate in profile 4. The C/N ratio values varied from 2.72 to 16.50 while soil contents of Ca2+, Mg2+, Na+ and K+ variations were according to C and N. The most abundant cations in land was Ca2+; followed by Mg2+, Na+ and K+ was the least abundant cationin soils. The factorial  correspondence analysis (FCA) showed two groups of soil according to  salinity and acidity mainly depending to high and low salinity respectively. This study showed two major constraints to land productivity in the village of Mboltime which are the salinity and the acidity of soils.Keywords : Soil, soil profile, salinity, Niayes, Senega

Transcriptional Profiling in Pathogenic and Non-Pathogenic SIV Infections Reveals Significant Distinctions in Kinetics and Tissue Compartmentalization

Simian immunodeficiency virus (SIV) infection leads to AIDS in experimentally infected macaques, whereas natural reservoir hosts exhibit limited disease and pathology. It is, however, unclear how natural hosts can sustain high viral loads, comparable to those observed in the pathogenic model, without developing severe disease. We performed transcriptional profiling on lymph node, blood, and colon samples from African green monkeys (natural host model) and Asian pigtailed macaques (pathogenic model) to directly compare gene expression patterns during acute pathogenic versus non-pathogenic SIV infection. The majority of gene expression changes that were unique to either model were detected in the lymph nodes at the time of peak viral load. Results suggest a shift toward cellular stress pathways and Th1 profiles during pathogenic infection, with strong and sustained type I and II interferon responses. In contrast, a strong type I interferon response was initially induced during non-pathogenic infection but resolved after peak viral load. The natural host also exhibited controlled Th1 profiles and better preservation of overall cell homeostasis. This study identified gene expression patterns that are specific to disease susceptibility, tissue compartmentalization, and infection duration. These patterns provide a unique view of how host responses differ depending upon lentiviral infection outcome

Critical Loss of the Balance between Th17 and T Regulatory Cell Populations in Pathogenic SIV Infection

Chronic immune activation and progression to AIDS are observed after SIV infection in macaques but not in natural host primate species. To better understand this dichotomy, we compared acute pathogenic SIV infection in pigtailed macaques (PTs) to non-pathogenic infection in African green monkeys (AGMs). SIVagm-infected PTs, but not SIVagm-infected AGMs, rapidly developed systemic immune activation, marked and selective depletion of IL-17-secreting (Th17) cells, and loss of the balance between Th17 and T regulatory (Treg) cells in blood, lymphoid organs, and mucosal tissue. The loss of Th17 cells was found to be predictive of systemic and sustained T cell activation. Collectively, these data indicate that loss of the Th17 to Treg balance is related to SIV disease progression

Innate immunity against HIV: a priority target for HIV prevention research

This review summarizes recent advances and current gaps in understanding of innate immunity to human immunodeficiency virus (HIV) infection, and identifies key scientific priorities to enable application of this knowledge to the development of novel prevention strategies (vaccines and microbicides). It builds on productive discussion and new data arising out of a workshop on innate immunity against HIV held at the European Commission in Brussels, together with recent observations from the literature

Socializing One Health: an innovative strategy to investigate social and behavioral risks of emerging viral threats

In an effort to strengthen global capacity to prevent, detect, and control infectious diseases in animals and people, the United States Agency for International Development’s (USAID) Emerging Pandemic Threats (EPT) PREDICT project funded development of regional, national, and local One Health capacities for early disease detection, rapid response, disease control, and risk reduction. From the outset, the EPT approach was inclusive of social science research methods designed to understand the contexts and behaviors of communities living and working at human-animal-environment interfaces considered high-risk for virus emergence. Using qualitative and quantitative approaches, PREDICT behavioral research aimed to identify and assess a range of socio-cultural behaviors that could be influential in zoonotic disease emergence, amplification, and transmission. This broad approach to behavioral risk characterization enabled us to identify and characterize human activities that could be linked to the transmission dynamics of new and emerging viruses. This paper provides a discussion of implementation of a social science approach within a zoonotic surveillance framework. We conducted in-depth ethnographic interviews and focus groups to better understand the individual- and community-level knowledge, attitudes, and practices that potentially put participants at risk for zoonotic disease transmission from the animals they live and work with, across 6 interface domains. When we asked highly-exposed individuals (ie. bushmeat hunters, wildlife or guano farmers) about the risk they perceived in their occupational activities, most did not perceive it to be risky, whether because it was normalized by years (or generations) of doing such an activity, or due to lack of information about potential risks. Integrating the social sciences allows investigations of the specific human activities that are hypothesized to drive disease emergence, amplification, and transmission, in order to better substantiate behavioral disease drivers, along with the social dimensions of infection and transmission dynamics. Understanding these dynamics is critical to achieving health security--the protection from threats to health-- which requires investments in both collective and individual health security. Involving behavioral sciences into zoonotic disease surveillance allowed us to push toward fuller community integration and engagement and toward dialogue and implementation of recommendations for disease prevention and improved health security