Structure d'âge et croissance de Clarias anguillaris (Pisces, Clariidae) dans le Delta Central du Niger au Mali (Afrique de l’Ouest)

L’étude de l’âge et de la croissance de C. anguillaris dans le Delta Central du Niger a porté sur 390 individus, de taille comprise entre 144 et 670 mm et échantillonnés sur un cycle annuel. L'âge individuel des poissons a été déterminé par squelettochronologie au moyen des coupes transversales de rayons épineux pectoraux dont l'épaisseur était de 100 μm. La validité des lectures d'âge a été appréciée par le calcul des indices de cohérence inter-lecteurs. L’évolution mensuelle de la marge relative du diamètre (dr) de la coupe du rayon épineux a été utilisée pour déterminer la périodicité de formation des marques de croissance et le cycle saisonnier de croissance. Ce dernier se caractérise par l'absence d'une période tranchée d'arrêt de croissance même si une reprise précoce, dès l'étiage, liée à une amélioration des conditions physico-chimiques et alimentaires, est observée. La longévité au sein de la population est de 4 ans bien qu’une forte proportion soit pêchée avant 2 ans d’âge. Le modèle théorique de croissance révèle, outre la grande taille que pourraient atteindre certains individus, une très importante croissance linéaire la première année avec 244.81±12.15 mm, ce qui augure de très bonnes performances aquacoles.Mots clés: Clarias anguillaris, squelettochronologie, marques de croissance, longévité, Delta Central du Niger, Mal

Fine Pathogen Discrimination within the APL1 Gene Family Protects Anopheles gambiae against Human and Rodent Malaria Species

Genetically controlled resistance of Anopheles gambiae mosquitoes to Plasmodium falciparum is a common trait in the natural population, and a cluster of natural resistance loci were mapped to the Plasmodium-Resistance Island (PRI) of the A. gambiae genome. The APL1 family of leucine-rich repeat (LRR) proteins was highlighted by candidate gene studies in the PRI, and is comprised of paralogs APL1A, APL1B and APL1C that share ≥50% amino acid identity. Here, we present a functional analysis of the joint response of APL1 family members during mosquito infection with human and rodent Plasmodium species. Only paralog APL1A protected A. gambiae against infection with the human malaria parasite P. falciparum from both the field population and in vitro culture. In contrast, only paralog APL1C protected against the rodent malaria parasites P. berghei and P. yoelii. We show that anti-P. falciparum protection is mediated by the Imd/Rel2 pathway, while protection against P. berghei infection was shown to require Toll/Rel1 signaling. Further, only the short Rel2-S isoform and not the long Rel2-F isoform of Rel2 confers protection against P. falciparum. Protection correlates with the transcriptional regulation of APL1A by Rel2-S but not Rel2-F, suggesting that the Rel2-S anti-parasite phenotype results at least in part from its transcriptional control over APL1A. These results indicate that distinct members of the APL1 gene family display a mutually exclusive protective effect against different classes of Plasmodium parasites. It appears that a gene-for-pathogen-class system orients the appropriate host defenses against distinct categories of similar pathogens. It is known that insect innate immune pathways can distinguish between grossly different microbes such as Gram-positive bacteria, Gram-negative bacteria, or fungi, but the function of the APL1 paralogs reveals that mosquito innate immunity possesses a more fine-grained capacity to distinguish between classes of closely related eukaryotic pathogens than has been previously recognized

Polymorphisms in Anopheles gambiae Immune Genes Associated with Natural Resistance to Plasmodium falciparum

Many genes involved in the immune response of Anopheles gambiae, the main malaria vector in Africa, have been identified, but whether naturally occurring polymorphisms in these genes underlie variation in resistance to the human malaria parasite, Plasmodium falciparum, is currently unknown. Here we carried out a candidate gene association study to identify single nucleotide polymorphisms (SNPs) associated with natural resistance to P. falciparum. A. gambiae M form mosquitoes from Cameroon were experimentally challenged with three local wild P. falciparum isolates. Statistical associations were assessed between 157 SNPs selected from a set of 67 A. gambiae immune-related genes and the level of infection. Isolate-specific associations were accounted for by including the effect of the isolate in the analysis. Five SNPs were significantly associated to the infection phenotype, located within or upstream of AgMDL1, CEC1, Sp PPO activate, Sp SNAKElike, and TOLL6. Low overall and local linkage disequilibrium indicated high specificity in the loci found. Association between infection phenotype and two SNPs was isolate-specific, providing the first evidence of vector genotype by parasite isolate interactions at the molecular level. Four SNPs were associated to either oocyst presence or load, indicating that the genetic basis of infection prevalence and intensity may differ. The validity of the approach was verified by confirming the functional role of Sp SNAKElike in gene silencing assays. These results strongly support the role of genetic variation within or near these five A. gambiae immune genes, in concert with other genes, in natural resistance to P. falciparum. They emphasize the need to distinguish between infection prevalence and intensity and to account for the genetic specificity of vector-parasite interactions in dissecting the genetic basis of Anopheles resistance to human malaria

Abreuvement des animaux domestiques en régions chaudes : aspects physiologiques et zootechniques

L'abreuvement des animaux domestiques en régions chaudes arides et semi-arides constitue sans conteste un problème crucial surtout pendant la saison sèche. Ainsi la quantité d'eau et le rythme d'abreuvement auront une influence certaine sur la physiologie et les performances zootechniques des animaux. Dans ce travail, les auteurs rapportent les résultats d'essais réalisés sur le sujet. Il apparait que la qualité de l'eau (caractéristiques physico-chimiques essentiellement) et l'abreuvement espacé ont des conséquences sur la physiologie (fonctions excrétrices urinaire et fécale, la thermorégulation, le milieu intérieur...) et les performances zootechniques (production et reproduction) des animaux domestiques [Résumé d'auteur

School-aged children based seasonal malaria chemoprevention using artesunate-amodiaquine in Mali

Introduction: Malaria is still a public health problem in Africa. Seasonal Malaria Chemoprevention (SMC) is an efficient control strategy recommended by WHO that targets children under five year old living in areas of seasonal malaria transmission. SMC uses the combination amodiaquine (AQ) – sulfadoxine-pyrimethamine (SP). However SP selects rapidly drug resistant parasites. And malaria burden may increase in older children where SMC is implemented. We initiated a pilot study to assess an alternative approach to SMC in older children in Mali. Methods: A randomized open-label clinical trial was conducted to test the efficacy and safety of SMC using artesunate – amodiaquine in school aged children in Mali. Two hundred pupils aged 6–15 years old were enrolled and randomized into two arms of 100 each, to receive either artesunate–amodiaquine (ASAQ) monthly or no intervention. Both arms were followed and clinical malaria were diagnosed and treated with arthemeter-lumefanthrine as recommended by Mali National Malaria Control Program. ASAQ was administered 3 days under study team direct observation and during 4 consecutive months starting in October 2013. Follow up was continued until April 2014. Results: Overall, 20 cases of uncomplicated clinical malaria were encountered in the Control arm and three cases in the ASAQ arm, showing a protective efficacy of 85% 95% CI [80.1–89.9] against clinical malaria. Protective efficacy against malaria infection was 69.6% 95% CI [58.6–21.4]. No effect on anemia was observed. ASAQ was well tolerated. Most common solicited adverse events were abdominal pain and headaches of mild intensity in respectively 64% and 44% of children that swallowed ASAQ. Conclusion: ASAQ is effective and well tolerated as SMC targeting older children in a peri urban setting in Mali. Its administration at schools is a feasible and accepted strategy to deliver the intervention. Keywords: School-aged children, Artesunate–amodiaquine (ASAQ), Seasonal malaria chemoprevention (SMC), School-based interventions, Malaria elimination, Peri-urban, Mal

Virgibacillus doumboii sp. nov., a halophilic bacterium isolated from the stool of a healthy child in Mali

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Virgibacillus ihumii sp. nov., a new bacterium isolated from the stool of healthy African children

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