Les hôtes réservoirs du virus de la striure du maïs (MSV) en zone soudano-sahélienne : identification et distribution spatio-temporelle

Une vaste prospection dans la flore herbacée du Burkina Faso à différentes périodes de l'année et pendant 3 ans a permis de collecter 41 espèces de Poaceae portant les symptômes de la striure du maïs. En utilisant le test immuno-enzymatique ELISA, il a été possible de détecter le virus de la striure du maïs (MSV) dans 35 échantillons. Le virus a pu être également transmis au maïs (Zea mays) par la cicadelle, Cicadulina triangula [Homoptera: Ciccadellidae] à partir de 32 de ces hôtes. Vingt quatre des hôtes du MSV ainsi identifiés n'avaient jamais été encore rapportés comme tel. L'étude de la répartition spatio-temporelle des réservoirs a permis d'obtenir trois résultats importants: a) c'est dans la zone de maïsiculture que les réservoirs sont les plus abondants; b) l'incidence de la maladie dans les champs de maïs est proportionnelle à l'abondance des réservoirs; c) c'est seulement 3 à 4 semaines après le début de la saison des pluies que la quantité de réservoirs devient importante. Il est conclu que des semis précoces devraient permettre de minimiser l'effet de la maladie sur les rendements du maïs.An intensive survey of herbaceous plants of Burkina Faso was carried out at different periods of the year during 3 yr. This permitted the collection of 41 Poaceae species showing maize streak symptoms. Using the ELISA method, maize streak virus (MSV) was detected in 35 samples. Transmission of the virus to corn (Zea mays) with the use of the leaf hopper Cicadulina triangula [Horroptera: Ciccadellidae], was possible for 32 of the 35 host samples tested.Twenty-four of these reservoirs have not been reported elsewhere as hosts of MSV. A study of the spatio-temporal distribution of reservoirs led us to three important conclusions: a) corn production areas are the most vulnerable zones for reservoir abundance; b) disease incidence on corn in the field is proportional to reservoir abundance; c) reservoirs increase rapidly within 3 or 4 week of rainfall after the beginning of the rain season. It is suggested that maize should be sown early in order to reduce incidence of MSV in Burkina Faso

Variabilité du virus de la striure du maïs (MSV) en zone soudano-sahélienne

Une étude de la variabilité du virus de la striure du maïs (MSV) a été réalisée au Burkina Faso, situé dans la zone soudano-sahélienne. De 1990 à 1992, 1240 échantillons ont été prélevés sur 36 hôtes naturellement infectés par le virus. Ils ont été analysés à l'aide du test ELISA, en utilisant cinq anticorps monoclonaux préparés contre le virus et par transmission du virus à quelques hôtes naturels. Trois variants sérologiques du virus, désignés par SK, VD114 et VD180, ont été caractérisés. D'autre part, il s'est avéré qu'il existait deux formes symptomatiques du variant SK soit SKF induisant des symptômes prononcés et SKf, des symptômes faibles. Chez le maïs (Zea mays), en infection mixte, le variant SK masquait les deux autres variants du MSV. L'apparente uniformité antigénique des isolats MSV du maïs observée par plusieurs auteurs a été attribuée à ce phénomène de masquage.A study of the variability of the maize streak virus (MSV) was conducted in Burkina Faso, which is part of the Sudano-Sahelian region. From 1990 to 1992, 1240 samples were collected on 36 hosts naturally infected by the virus. These samples were analysed with ELISA, using five monoclonal antibodies developed against the MSV and by transmission of the virus to some natural hosts. Three serological variants of the virus, designated as SK, VD114, and VD180 were characterized. The SK variant was further divided into two forms, namely SKF and SKf, which induced severe and mild symptoms, respectively. In maize (Zea mays), with multiple infection, the SK variant masked the other two MSV variants. The apparent antigenic uniformity of the MSV isolates from maize observed by many authors has been linked with this masking effect

Phytochemical composition, Antioxidant and Anti-inflammatory potential of bioactive fractions from extracts of three medicinal plants traditionally used to treat liver diseases in Burkina Faso

Our aim in this study concerning the ethyl acetate and dichloromethane fractions was to provide a scientific basis for the treatment of hepatitis B in Burkina Faso of these three ethnomedicinal plants. As a result, we evaluated polyphenol content, antioxidant and anti-inflammatory evaluated by lipoxygenase (LOX) inhibitory and Xanthine Oxidase (XO) activities of aqueous acetone bioactive fractions from three species of Malvaceae (Sida cordifolia, Sida rhombifolia, S. urens). Folin-ciocalteu; AlCl3 methods and tannic acid respectively were used for polyphenol content research. The antioxidant activity of the samples was evaluate using three separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydramzyl (DPPH), ABTS radical cation decolorization assay, Iron (III) to iron (II) reduction activity (FRAP). For anti-inflammatoty activity, lypoxygenase and xanthine oxidase inhibitory activities were used. Finally, in this study, the ethyl acetate fraction has shown the best results comparatively to the dichloromethane fraction. Keywords: Polyphenol, Antioxidant, anti-inflammatory, Medicinal plants, hepatitis B

Phytochemical composition, Antioxidant and Anti-inflammatory potential of bioactive fractions from extracts of three medicinal plants traditionally used to treat liver diseases in Burkina Faso

Our aim in this study concerning the ethyl acetate and dichloromethane fractions was to provide a scientific basis for the treatment of hepatitis B in Burkina Faso of these three ethnomedicinal plants. As a result, we evaluated polyphenol content, antioxidant and anti-inflammatory evaluated by lipoxygenase (LOX) inhibitory and Xanthine Oxidase (XO) activities of aqueous acetone bioactive fractions from three species of Malvaceae (Sida cordifolia, Sida rhombifolia, S. urens). Folin-ciocalteu; AlCl3 methods and tannic acid respectively were used for polyphenol content research. The antioxidant activity of the samples was evaluate using three separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydramzyl (DPPH), ABTS radical cation decolorization assay, Iron (III) to iron (II) reduction activity (FRAP). For anti-inflammatoty activity, lypoxygenase and xanthine oxidase inhibitory activities were used. Finally, in this study, the ethyl acetate fraction has shown the best results comparatively to the dichloromethane fraction. Keywords: Polyphenol, Antioxidant, anti-inflammatory, Medicinal plants, hepatitis B

The intensification of thermal extremes in west Africa

International audienceThis study aims in filling the gap in understanding the relationship between trend and extreme in diurnal and nocturnal temperatures (Tx and Tn) over the Gulf of Guinea area and the Sahel. Time-evolution and trend of Tx and Tn anomalies, extreme temperatures and heat waves are examined using regional and station-based indices over the 1900–2012 and 1950–2012 periods respectively. In investigating extreme temperature anomalies and heat waves, a percentile method is used. At the regional and local scales, rising trends in Tx and Tn anomalies, which appear more pronounced over the past 60 years, are identified over the two regions. The trends are characterized by an intensification of: i) nocturnal/Tn warming over the second half of the 20th century; and ii) diurnal/Tx warming over the post-1980s. This is the same scheme with extreme warm days and warm nights. Finally annual number of diurnal and nocturnal heat waves has increase over the Gulf of Guinea coastal regions over the second half of the 20th century, and even more substantially over the post-1980s period. Although this trend in extreme warm days and nights is always overestimated in the simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), those models display rising trends whatever the scenario, which are likely to be more and more pronounced over the two regions in the next 50 years

Intermittent Preventive Treatment to Reduce the Burden of Malaria in Children: New Evidence on Integration and Delivery

James Beeson and colleagues discuss three new studies in PLoS Medicine that provide valuable evidence on how to delivery and integrate intermittent preventive reatment for malaria in children (IPTc)

Molecular diversity of Cotton leaf curl Gezira virus isolates and their satellite DNAs associated with okra leaf curl disease in Burkina Faso

Okra leaf curl disease (OLCD) is a major constraint on okra (Abelmoschus esculentus) production and is widespread in Africa. Using a large number of samples representative of the major growing regions in Burkina Faso (BF), we show that the disease is associated with a monopartite begomovirus and satellite DNA complexes. Twenty-three complete genomic sequences of Cotton leaf curl Gezira virus (CLCuGV) isolates associated with OLCD, sharing 95 to 99% nucleotide identity, were cloned and sequenced. Six betasatellite and four alphasatellite (DNA-1) molecules were also characterized. The six isolates of betasatellite associated with CLCuGV isolates correspond to Cotton leaf curl Gezira betasatellite (CLCuGB) (88 to 98% nucleotide identity). One isolate of alphasatellite is a variant of Cotton leaf curl Gezira alphasatellite (CLCuGA) (89% nucleotide identity), whereas the three others isolates appear to correspond to a new species of alphasatellite (CLCuGA most similar sequence present 52 to 60% nucleotide identity), provisionally named Okra leaf curl Burkina Faso alphasatellite (OLCBFA). Recombination analysis of the viruses demonstrated the interspecies recombinant origin of all CLCuGV isolates, with parents being close to Hollyhock leaf crumple virus (AY036009) and Tomato leaf curl Diana virus (AM701765). Combined with the presence of satellites DNA, these results highlight the complexity of begomoviruses associated with OLCD

Multiple small-effect alleles of Indica origin enhance high iron-associated stress tolerance in rice under field conditions in west Africa

Open Access Journal; Published online: 15 Jan 2021Understanding the genetics of field-based tolerance to high iron-associated (HIA) stress in rice can accelerate the development of new varieties with enhanced yield performance in West African lowland ecosystems. To date, few field-based studies have been undertaken to rigorously evaluate rice yield performance under HIA stress conditions. In this study, two NERICA × O. sativa bi-parental rice populations and one O.sativa diversity panel consisting of 296 rice accessions were evaluated for grain yield and leaf bronzing symptoms over multiple years in four West African HIA stress and control sites. Mapping of these traits identified a large number of QTLs and single nucleotide polymorphisms (SNPs) associated with stress tolerance in the field. Favorable alleles associated with tolerance to high levels of iron in anaerobic rice soils were rare and almost exclusively derived from the indica subpopulation, including the most favorable alleles identified in NERICA varieties. These findings highlight the complex genetic architecture underlying rice response to HIA stress and suggest that a recurrent selection program focusing on an expanded indica genepool could be productively used in combination with genomic selection to increase the efficiency of selection in breeding programs designed to enhance tolerance to this prevalent abiotic stress in West Africa

Impact of combining intermittent preventive treatment with home management of malaria in children less than 10 years in a rural area of Senegal: a cluster randomized trial

<p>Abstract</p> <p>Background</p> <p>Current malaria control strategies recommend (i) early case detection using rapid diagnostic tests (RDT) and treatment with artemisinin combination therapy (ACT), (ii) pre-referral rectal artesunate, (iii) intermittent preventive treatment and (iv) impregnated bed nets. However, these individual malaria control interventions provide only partial protection in most epidemiological situations. Therefore, there is a need to investigate the potential benefits of integrating several malaria interventions to reduce malaria prevalence and morbidity.</p> <p>Methods</p> <p>A randomized controlled trial was carried out to assess the impact of combining seasonal intermittent preventive treatment in children (IPTc) with home-based management of malaria (HMM) by community health workers (CHWs) in Senegal. Eight CHWs in eight villages covered by the Bonconto health post, (South Eastern part of Senegal) were trained to diagnose malaria using RDT, provide prompt treatment with artemether-lumefantrine for uncomplicated malaria cases and pre-referral rectal artesunate for complicated malaria occurring in children under 10 years. Four CHWs were randomized to also administer monthly IPTc as single dose of sulphadoxine-pyrimethamine (SP) plus three doses of amodiaquine (AQ) in the malaria transmission season, October and November 2010. Primary end point was incidence of single episode of malaria attacks over 8 weeks of follow up. Secondary end points included prevalence of malaria parasitaemia, and prevalence of anaemia at the end of the transmission season. Primary analysis was by intention to treat. The study protocol was approved by the Senegalese National Ethical Committee (approval 0027/MSP/DS/CNRS, 18/03/2010).</p> <p>Results</p> <p>A total of 1,000 children were enrolled. The incidence of malaria episodes was 7.1/100 child months at risk [95% CI (3.7-13.7)] in communities with IPTc + HMM compared to 35.6/100 child months at risk [95% CI (26.7-47.4)] in communities with only HMM (aOR = 0.20; 95% CI 0.09-0.41; <it>p </it>= 0.04). At the end of the transmission season, malaria parasitaemia prevalence was lower in communities with IPTc + HMM (2.05% versus 4.6% <it>p </it>= 0.03). Adjusted for age groups, sex, <it>Plasmodium falciparum </it>carriage and prevalence of malnutrition, IPTc + HMM showed a significant protective effect against anaemia (aOR = 0.59; 95% CI 0.42-0.82; <it>p </it>= 0.02).</p> <p>Conclusion</p> <p>Combining IPTc and HMM can provide significant additional benefit in preventing clinical episodes of malaria as well as anaemia among children in Senegal.</p