La lutte contre les schistosomoses en Afrique de l'Ouest

La bilharziose uro-génitale est connue au Sénégal depuis plus d'un siècle, et sa présence est signalée dans tout le pays. La bilharziose intestinale était décrite sous forme de foyers isolés et peu intenses jusqu'à l'épidémie de Richard Toll favorisée par la mise ne service des barrages de Manantali et Diama. La distribution des hôtes intermédiaires recouvre les informations épidémiologiques disponibles. Le risque d'extension des foyers, notamment à la faveur des aménagements hydroagricoles, est discuté. Un programme national de lutte a été initié en 1999 et devrait incessamment être mis en oeuvre. (Résumé d'auteur

Aménagements hydro-agricoles et santé (vallée du fleuve Sénégal)

Près de 1 500 personnes résidant dans les villages rattachés au périmètre irrigué MO 6bis (périmètre de Diomandou, département de Podor) ont fait l'objet de prélèvements d'urine et/ou de selle afin de déterminer la prévalence de la bilharziose urinaire, de la bilharziose intestinale ainsi que des autres parasitoses entériques. Chez les riverains du périmètre, 1 295 urines ont été examinées, parmi lesquelles sept contenaient des oeufs viables de #Schistosoma haematobium$, ce qui représente un taux de prévalence de 0,5$, ce qui correspond à un indice d'infestation de 0,1%. Il s'agissait là aussi d'un individu dont la contamination avait eu lieu en dehors de la zone d'étude. #Eschirichia coli$est la parasite entérique le plus répandu avec 17,2$, #Strongyloïdes stercoralis, #Ascaris lumbricoïdes et #Trichiuris trichiura$ sont rares et ne concernent qu'un peu moins de 2% des sujets examinés. Ces résultats démontrent l'absence, pour l'instant tout au moins, de foyers de transmission des bilharzioses dans les villages du périmètre de Diomandou. Le risque d'apparition de ces maladies est cependant important et dépend à la fois de l'évolution des infrastructures et de l'éventuelle apparition d'hôtes intermédiaires encore absent du réseau hydrographique de ce périmètre mis en place récemment. (Résumé d'auteur

Segregation Distortions in an Interspecific Cotton Population issued from the [(Gossypium hirsutum x G. raimondii)² x G. sturtianum] Hybrid

The segregation ratio of 10 Gossypium sturtianum specific SSR markers belonging to linkage groups c2-c14, c3-c17, and c6-c25 was analysed in the BC2S6 progeny of the [G. hirsutum x G. raimondii)² x G. sturtianum] (HRS) hybrid; based on chi-square test. All the marker loci tested were associated with skewed allele frequencies (P<0.001) showing a strong SD with a zygotic selection. The possible causes and consequences of this massive segregation distortion are discussed

A Systematic Map of Genetic Variation in Plasmodium falciparum

Discovering novel genes involved in immune evasion and drug resistance in the human malaria parasite, Plasmodium falciparum, is of critical importance to global health. Such knowledge may assist in the development of new effective vaccines and in the appropriate use of antimalarial drugs. By performing a full-genome scan of allelic variability in 14 field and laboratory strains of P. falciparum, we comprehensively identified ≈500 genes evolving at higher than neutral rates. The majority of the most variable genes have paralogs within the P. falciparum genome and may be subject to a different evolutionary clock than those without. The group of 211 variable genes without paralogs contains most known immunogens and a few drug targets, consistent with the idea that the human immune system and drug use is driving parasite evolution. We also reveal gene-amplification events including one surrounding pfmdr1, the P. falciparum multidrug-resistance gene, and a previously uncharacterized amplification centered around the P. falciparum GTP cyclohydrolase gene, the first enzyme in the folate biosynthesis pathway. Although GTP cyclohydrolase is not the known target of any current drugs, downstream members of the pathway are targeted by several widely used antimalarials. We speculate that an amplification of the GTP cyclohydrolase enzyme in the folate biosynthesis pathway may increase flux through this pathway and facilitate parasite resistance to antifolate drugs

Ivermectin, ‘Wonder drug’ from Japan: the human use perspective

Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of avermectin—originating solely from a single microorganism isolated at the Kitasato Intitute, Tokyo, Japan from Japanese soil—has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world’s most devastating and disfiguring diseases which have plagued the world’s poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally. It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin’s passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a “wonder” drug

Effect of GammaRay in the Progeny of Trispecific Hybrid [(Gossypium hirsutum x G. raimondii)² x G. sturtianum]

The objective of this study is to analyse the possibilities of fixing in the progeny of the [(Gossypium hirsutum x G. raimondii)² x G. sturtianum] (HRS) trispecies hybrid, the glandless-seed and glanded-plant trait. The expression of the character was analysed in progenies obtained by selfing the HRS BC2S5/9/6/1/51/15 genetic stock. This character is controlled by one or more genes located on introgressed chromosome fragments of G. sturtianum. These foreign DNA fragments seem also carriers of gametes terminators genes on the same chromosome fragments and there would be a possible existence of negative interactions between some of the introgressed G. sturtianum alleles and the G. hirsutum genetic background inducing post-zygotic mortality. In order to break existing lethal links, some of the studied seeds were treated with 15 krad of gamma radiation. The transfer of G. sturtianum chromosome fragments introgressed stocks was assessed using ten mapped SSR markers, carried out on 78 plants HRS ‘BC2S6’. Gamma irradiation used to overcome lethality in HRS hybrid did not give expected results in M2 because of high rate of abortion observed in HRS ‘BC2S6’ seeds. However, gamma ray did not induce the appearance of chimeric tissues in the HRS ‘BC2S5/9/6/1/51/15’ in M1 plants. Moreover, the notable fertility improvement observed for some plants issued from irradiated seeds constitutes a clue of the achievement of favourables recombinations due to the gamma ray treatment. The perspectives opened by the results obtained for the stabilization of the glandless-seed and glanded-plant trait in a G. hirsutum commercial variety are discussed