Variabilité Intra-saisonnière des Pluies et Production du Sorgho en Zones Soudanienne et Sahélienne du Mali

           L’agriculture malienne, pilier du développement économique et de la sécurité alimentaire des populations, est affectée par les dérèglements climatiques en raison de son caractère essentiellement pluvial. La présente recherche a pour objectif d’analyser les effets de l’instabilité intra-saisonnière des pluies afin d’identifier les périodes optimales de semis du sorgho en zones soudanienne et sahélienne du Mali. A partir des hauteurs journalières de pluie de la station de Katibougou et de San entre 1987 et 2018 fournies par l’Agence pour la Sécurité et la Navigation Aérienne (ASECNAC) du Mali, les dates de début et de fin de saison ont été déterminées. Ensuite, l’analyse fréquentielle du début, de la fin et de la longueur des saisons a été faite aux fréquences de 2, 5 et 8 années sur 10. De même, la fréquence des séquences sèches et humides pendant la saison culturale a été analysée. Les résultats ont montré que dans le cercle de Koulikoro, les dates probables des démarrages de la pluie se situent entre le 06 mai et le 01 août de chaque année. Par contre à San, les dates probables des démarrages de la pluie se situent entre le 12 mai et le 01 août de chaque année.  A Koulikoro, la fin de la saison pluvieuse se situe généralement entre le 06 septembre et le 04 novembre. A San, la fin de la saison pluvieuse se situe généralement entre le 03 septembre et le 02 novembre. Les poches de sècheresse de 5 jours (SS1) sont les pauses pluviométriques constatées dans le cercle de Koulikoro et elles décroissent au fur et à mesure jusqu’au mois de septembre. Les SS4 s’accroissent jusqu’à partir du mois de juillet à octobre. A San, les SS1 et SS4 sont similaires à ceux du cercle de Koulikoro. Par contre, les SS3 sont un peu élevés durant les mois de mai, juillet, août et septembre. Dans le cercle de Koulikoro sur 2, 5 et 8 années sur 10, la durée de la saison agricole est de 159, 132 et 102 jours. Dans ces conditions, la variété du sorgho de 90 jours et de 105 jours peut se cultiver normalement depuis la levée jusqu’à la maturation. Par contre à San, sur 2,5 et 8 années sur 10, la durée de la saison agricole est de 123, 108 et 89 jours, dans ces conditions, la variété du sorgho de 90 jours peut se cultiver normalement depuis la levée jusqu’à la maturation, par contre la variété de 90 est compromise sur 8 années sur 10  et  celle de 105 jours est compromise sur 5 et 8 années sur 10. Au regard de l’intérêt que les producteurs accordent à la culture du sorgho et de l’instabilité intra-saisonnière des pluies, ils s’approprient plusieurs mesures d’adaptation (planification du calendrier agricole, adoption de la variété culturale à cycle court, utilisation d’engrais) dont l’efficacité mérite d’être analysée.   Malian agriculture, a pillar of economic development and food security, is affected by climatic disturbances because of its essentially rainfed nature. The objective of this research is to analyse the effects of intra-seasonal rainfall instability in order to identify optimal sorghum sowing periods in the Sudanian and Sahelian zones of Mali. From the daily rainfall amounts of the Katibougou and San stations between 1987 and 2018 provided by the Malian Agency for Air Safety and Navigation (ASECNAC), the start and end of the season dates were determined. Then, the frequency analysis of the beginning, end and length of the seasons was done at frequencies of 2. 5 and 8 years out of 10. Similarly, the frequency of dry and wet sequences during the cropping season was analysed. The results showed that in the Koulikoro district, the probable dates for the start of rainfall are between 6 May and 1 August each year. In contrast, in San, the probable dates for the start of the rainfall are between 12 May and 1 August each year.  In Koulikoro, the end of the rainy season is generally between 6 September and 4 November. In San, the end of the rainy season is generally between 03 September and 02 November. The 5-day drought pockets (SS1) are the rainfall breaks observed in the Koulikoro district and they decrease progressively until September. SS4 increases from July to October. In San, SS1 and SS4 are similar to those in Koulikoro, but, SS3 is slightly higher in May, July, August and September. In the Koulikoro district, the length of the agricultural season in 2. 5 and 8 years out of 10 is 159. 132 and 102 days. Under these conditions, the 90-day and 105-day sorghum varieties can be grown normally from emergence to maturation. On the other hand, in San, over 2. 5 and 8 years out of 10, the length of the agricultural season is 123. 108 and 89 days, under these conditions, the 90-day sorghum variety can be grown normally from emergence to maturation, while the 90-day variety is compromised over 8 years out of 10 and the 105-day variety is compromised over 5 and 8 years out of 10. In view of the interest that producers have in growing sorghum and the intra-seasonal instability of rainfall, they have adopted several adaptation measures (planning of the agricultural calendar, adoption of the short-cycle crop variety, use of fertilisers), the effectiveness of which deserves to be analysed

Migration outflows and optimal migration policy: rules versus discretion

We study the effects of more open borders on return migration and show that migrants are more likely to return to the origin country when migration rules are softened, because this implies that they could more easily re-migrate if return migration is unsuccessful. As a result, softening migration rules leads to lower net inflows than is generally acknowledged. We show that if government follows rules to shape the optimal migration policy, it will choose more open “borders” than were its behaviour to be discretionary. However, this requires an appropriate commitment technology. We show that electoral accountability may be a solution to the commitment problem. As a matter of fact, observed softer immigration rules in western countries suggest the effectiveness of such a mechanism.info:eu-repo/semantics/publishedVersio

Population Structure of Staphylococcus aureus from Remote African Babongo Pygmies

Staphylococcus aureus is a bacterium that colonizes humans worldwide. The anterior nares are its main ecological niche. Carriers of S. aureus are at a higher risk of developing invasive infections. Few reports indicated a different clonal structure and profile of virulence factors in S. aureus isolates from Sub-Saharan Africa. As there are no data about isolates from remote indigenous African populations, we conducted a cross-sectional survey of S. aureus nasal carriage in Gabonese Babongo Pygmies. The isolates were characterized regarding their susceptibility to antibiotic agents, possession of virulence factors and clonal lineage. While similar carriage rates were found in populations of industrialized countries, isolates that encode the genes for the Panton-Valentine leukocidin (PVL) were clearly more prevalent than in European countries. Of interest, many methicillin-susceptible S. aureus isolates from Babongo Pygmies showed the same genetic background as pandemic methicillin-resistant S. aureus (MRSA) clones. We advocate a surveillance of S. aureus in neglected African populations to control the development of resistance to antibiotic drugs with particular respect to MRSA and to assess the impact of the high prevalence of PVL-positive isolates

Human malarial disease: a consequence of inflammatory cytokine release

Malaria causes an acute systemic human disease that bears many similarities, both clinically and mechanistically, to those caused by bacteria, rickettsia, and viruses. Over the past few decades, a literature has emerged that argues for most of the pathology seen in all of these infectious diseases being explained by activation of the inflammatory system, with the balance between the pro and anti-inflammatory cytokines being tipped towards the onset of systemic inflammation. Although not often expressed in energy terms, there is, when reduced to biochemical essentials, wide agreement that infection with falciparum malaria is often fatal because mitochondria are unable to generate enough ATP to maintain normal cellular function. Most, however, would contend that this largely occurs because sequestered parasitized red cells prevent sufficient oxygen getting to where it is needed. This review considers the evidence that an equally or more important way ATP deficency arises in malaria, as well as these other infectious diseases, is an inability of mitochondria, through the effects of inflammatory cytokines on their function, to utilise available oxygen. This activity of these cytokines, plus their capacity to control the pathways through which oxygen supply to mitochondria are restricted (particularly through directing sequestration and driving anaemia), combine to make falciparum malaria primarily an inflammatory cytokine-driven disease

Acute disseminated encephalomyelitis after dengue

Dengue fever, transmitted by Aedes aegypti mosquitoes, is one of the most common vector-borne disease. Its incidence is increasing steadily worldwide, becoming a major public health problem in the tropical and subtropical zone. Neurological manifestations after dengue are not very common and acute disseminated encephalomyelitis (ADEM) following dengue infections is rare with a few cases documented in literature. Clinical characteristics and typical lesions of ADEM on magnetic resonance imaging (MRI) of brain along with serologic positivity for dengue usually confirm the diagnosis. We report a case of ADEM which developed as a neurological complication of dengue during an epidemic in a 39-year-old woman

Persistent Plasmodium falciparum infection in women with an intent to become pregnant as a risk factor for pregnancy-associated malaria

Background. Pregnant women are more susceptible to Plasmodium falciparum than before pregnancy, and infection has consequences for both mother and offspring. The World Health Organization recommends that pregnant woman in areas of transmission receive intermittent preventive treatment (IPTp) starting in the second trimester. Consequently, women are not protected during the first trimester, although P. falciparum infections are both frequent and harmful. Methods. A cohort of nulligravid women was followed up during subsequent pregnancy. Malaria was diagnosed by means of microscopy and polymerase chain reaction. Parasites were genotyped at polymorphic loci. Results. Among 275 nulligravidae enrolled, 68 women became pregnant and were followed up during pregnancy. Before pregnancy, P. falciparum prevalence rates were 15% by microscopy and 66% by polymerase chain reaction. Microscopic infection rates increased to 29% until IPTp administration, and their density increased by 20-fold. Conversely, submicroscopic infection rates decreased. After IPTp administration, all types of infections decreased, but they increased again late in pregnancy. The risk of infection during pregnancy was higher in women with a microscopic (odds ratio, 6.5; P = .047) or submicroscopic (3.06; P = .05) infection before pregnancy and was not related to the season of occurrence. Most infections during pregnancy were persistent infections acquired before pregnancy. Conclusions. Microscopic and submicroscopic malaria infections were frequent in nulligravid women from south Benin. During the first trimester of pregnancy, microscopic infections were more frequent, with a higher parasite density, and mainly derived from parasites infecting the woman before conception. Preventive strategies targeting nonpregnant women with a desire for conception need to be designed

Clinical development of a VAR2CSA-based placental malaria vaccine PAMVAC : quantifying vaccine antigen-specific memory B & T cell activity in Beninese primigravidae

Background: The antigen VAR2CSA plays a pivotal role in the pathophysiology of pregnancy-associated malaria (PAM) caused by Plasmodium falciparum. A VAR2CSA-based vaccine candidate, PAMVAC, is under development by an EU-funded multi-country consortium (PlacMalVac project). As part of PAMVACs clinical development, we quantified naturally acquired vaccine antigen-specific memory B and T cell responses in Beninese primigravidae recruited at the beginning of pregnancy and followed up to delivery and beyond. Methods: Clinical and parasitological histories were compiled from monthly clinic visits. On 4 occasions (first and fifth month of pregnancy, delivery, 6 months post-delivery) peripheral blood mononuclear cells were isolated for in vitro assays. PAMVAC-specific memory B cells as well as those specific for a PAM unrelated P. falciparum antigen (PfEMP1-CIDR1a) and for tetanus toxoid were quantified by ELISpot. Memory T cell responses were assessed by quantifying cytokines (IL-5, IL-6, IL-10, IL-13, IFN-gamma, TNF-alpha) in supernatants of cells stimulated in vitro either with PAMVAC, or mitogen (PHA). Results: Both tetanus toxoid- and PAMVAC-specific memory B cell frequencies increased to reach peak levels in the 5th month and at delivery, respectively and persisted post-delivery. The frequency of CIDR1a-specific memory B cells was stable during pregnancy, but declined post-delivery. The cumulated prevalence of infection with P. falciparum during pregnancy was 61% by microscopy. In women with a history of such infections, a significantly higher frequency of PAMVAC-specific memory B cells was observed at delivery. PAMVAC-specific pro-inflammatory (IFN-gamma, TNF) responses tended to be higher at delivery in those with a history of infection. Mitogen-induced IL-5/IL-13 responses were significantly enhanced in the same women. Conclusions: PAMVAC-specific memory B cells are induced during first pregnancies and are maintained post-delivery. Women with a T helper cell profile biased towards production of Th2-type cytokines have a greater risk of infection with P. falciparum

Efficacy and Safety of the RTS,S/AS01 Malaria Vaccine during 18 Months after Vaccination: A Phase 3 Randomized, Controlled Trial in Children and Young Infants at 11 African Sites

Background:A malaria vaccine could be an important addition to current control strategies. We report the safety and vaccine efficacy (VE) of the RTS,S/AS01 vaccine during 18 mo following vaccination at 11 African sites with varying malaria transmission.Methods and Findings:6,537 infants aged 6-12 wk and 8,923 children aged 5-17 mo were randomized to receive three doses of RTS,S/AS01 or comparator vaccine.VE against clinical malaria in children during the 18 mo after vaccine dose 3 (per protocol) was 46% (95% CI 42% to 50%) (range 40% to 77%; VE, p<0.01 across all sites). VE during the 20 mo after vaccine dose 1 (intention to treat [ITT]) was 45% (95% CI 41% to 49%). VE against severe malaria, malaria hospitalization, and all-cause hospitalization was 34% (95% CI 15% to 48%), 41% (95% CI 30% to 50%), and 19% (95% CI 11% to 27%), respectively (ITT).VE against clinical malaria in infants was 27% (95% CI 20% to 32%, per protocol; 27% [95% CI 21% to 33%], ITT), with no significant protection against severe malaria, malaria hospitalization, or all-cause hospitalization.Post-vaccination anti-circumsporozoite antibody geometric mean titer varied from 348 to 787 EU/ml across sites in children and from 117 to 335 EU/ml in infants (per protocol).VE waned over time in both age categories (Schoenfeld residuals p<0.001). The number of clinical and severe malaria cases averted per 1,000 children vaccinated ranged across sites from 37 to 2,365 and from -1 to 49, respectively; corresponding ranges among infants were -10 to 1,402 and -13 to 37, respectively (ITT). Meningitis was reported as a serious adverse event in 16/5,949 and 1/2,974 children and in 9/4,358 and 3/2,179 infants in the RTS,S/AS01 and control groups, respectively.Conclusions:RTS,S/AS01 prevented many cases of clinical and severe malaria over the 18 mo after vaccine dose 3, with the highest impact in areas with the greatest malaria incidence. VE was higher in children than in infants, but even at modest levels of VE, the number of malaria cases averted was substantial. RTS,S/AS01 could be an important addition to current malaria control in Africa.Trial registration:http://www.ClinicalTrials.gov NCT00866619. Please see later in the article for the Editors' Summary