Assessment of the relative success of sporozoite inoculations in individuals exposed to moderate seasonal transmission

Background: The time necessary for malaria parasite to re-appear in the blood following treatment (re-infection time) is an indirect method for evaluating the immune defences operating against pre-erythrocytic and early erythrocytic malaria stages. Few longitudinal data are available in populations in whom malaria transmission level had also been measured. Methods: One hundred and ten individuals from the village of Ndiop (Senegal), aged between one and 72 years, were cured of malaria by quinine (25 mg/day oral Quinimax T in three equal daily doses, for seven days). Thereafter, thick blood films were examined to detect the reappearance of Plasmodium falciparum every week, for 11 weeks after treatment. Malaria transmission was simultaneously measured weekly by night collection of biting mosquitoes. Results: Malaria transmission was on average 15.3 infective bites per person during the 77 days follow up. The median reappearance time for the whole study population was 46.8 days, whereas individuals would have received an average one infective bite every 5 days. At the end of the follow-up, after 77 days, 103 of the 110 individuals (93.6%; CI 95% [89.0-98.2]) had been re-infected with P. falciparum. The median reappearance time ('re-positivation') was longer in subjects with patent parasitaemia at enrolment than in parasitologically-negative individuals (58 days vs. 45.9; p = 0.03) and in adults > 30 years than in younger subjects (58.6 days vs. 42.7; p = 0.0002). In a multivariate Cox PH model controlling for the sickle cell trait, G6PD deficiency and the type of habitat, the presence of parasitaemia at enrolment and age >= 30 years were independently predictive of a reduced risk of re-infection (PH = 0.5 [95% CI: 0.3-0.9] and 0.4; [95% CI: 0.2-0.6] respectively). Conclusion: Results indicate the existence of a substantial resistance to sporozoites inoculations, but which was ultimately overcome in almost every individual after 2 1/2 months of natural challenges. Such a study design and the results obtained suggest that, despite a small sample size, this approach can contribute to assess the impact of intervention methods, such as the efficacy vector-control measures or of malaria pre-erythrocytic stages vaccines

An Exhaustive, Non-Euclidean, Non-Parametric Data Mining Tool for Unraveling the Complexity of Biological Systems – Novel Insights into Malaria

Complex, high-dimensional data sets pose significant analytical challenges in the post-genomic era. Such data sets are not exclusive to genetic analyses and are also pertinent to epidemiology. There has been considerable effort to develop hypothesis-free data mining and machine learning methodologies. However, current methodologies lack exhaustivity and general applicability. Here we use a novel non-parametric, non-euclidean data mining tool, HyperCube®, to explore exhaustively a complex epidemiological malaria data set by searching for over density of events in m-dimensional space. Hotspots of over density correspond to strings of variables, rules, that determine, in this case, the occurrence of Plasmodium falciparum clinical malaria episodes. The data set contained 46,837 outcome events from 1,653 individuals and 34 explanatory variables. The best predictive rule contained 1,689 events from 148 individuals and was defined as: individuals present during 1992–2003, aged 1–5 years old, having hemoglobin AA, and having had previous Plasmodium malariae malaria parasite infection ≤10 times. These individuals had 3.71 times more P. falciparum clinical malaria episodes than the general population. We validated the rule in two different cohorts. We compared and contrasted the HyperCube® rule with the rules using variables identified by both traditional statistical methods and non-parametric regression tree methods. In addition, we tried all possible sub-stratified quantitative variables. No other model with equal or greater representativity gave a higher Relative Risk. Although three of the four variables in the rule were intuitive, the effect of number of P. malariae episodes was not. HyperCube® efficiently sub-stratified quantitative variables to optimize the rule and was able to identify interactions among the variables, tasks not easy to perform using standard data mining methods. Search of local over density in m-dimensional space, explained by easily interpretable rules, is thus seemingly ideal for generating hypotheses for large datasets to unravel the complexity inherent in biological systems

Prevalence and factors associated with maternal and neonatal sepsis in sub-Saharan Africa: a systematic review and meta-analysis

ObjectivesThis study aimed to determine the prevalence and factors associated with maternal and neonatal sepsis in sub-Saharan Africa.MethodsThis systematic review and meta-analysis used the PRISMA guideline on sepsis data in sub-Saharan Africa. The bibliographic search was carried out on the following databases: Medline/PubMed, Cochrane Library, African Index Medicus, and Google Scholar. Additionally, the reference lists of the included studies were screened for potentially relevant studies. The last search was conducted on 15 October 2022. The Joanna Briggs Institute quality assessment checklist was applied for critical appraisal. Estimates of the prevalence of maternal and neonatal sepsis were pooled using a random-effects meta-analysis model. Heterogeneity between studies was estimated using the Q statistic and the I2 statistic. The funnel plot and Egger’s regression test were used to assess the publication bias.ResultsA total of 39 studies were included in our review: 32 studies on neonatal sepsis and 7 studies on maternal sepsis. The overall pooled prevalence of maternal and neonatal sepsis in Sub-Saharan Africa was 19.21% (95% CI, 11.46–26.97) and 36.02% (CI: 26.68–45.36), respectively. The meta-analyses revealed that Apgar score < 7 (OR: 2.4, 95% CI: 1.6–3.5), meconium in the amniotic fluid (OR: 2.9, 95% CI: 1.8–4.5), prolonged rupture of membranes >12 h (OR: 2.8, 95% CI: 1.9–4.1), male sex (OR: 1.2, 95% CI: 1.1–1.4), intrapartum fever (OR: 2.4, 95% CI: 1.5–3.7), and history of urinary tract infection in the mother (OR: 2.7, 95% CI: 1.4–5.2) are factors associated with neonatal sepsis. Rural residence (OR: 2.3, 95% CI: 1.01–10.9), parity (OR: 0.5, 95% CI: 0.3–0.7), prolonged labor (OR: 3.4, 95% CI: 1.6–6.9), and multiple digital vaginal examinations (OR: 4.4, 95% CI: 1.3–14.3) were significantly associated with maternal sepsis.ConclusionThe prevalence of maternal and neonatal sepsis was high in sub-Saharan Africa. Multiple factors associated with neonatal and maternal sepsis were identified. These factors could help in the prevention and development of strategies to combat maternal and neonatal sepsis. Given the high risk of bias and high heterogeneity, further high-quality research is needed in the sub-Saharan African context, including a meta-analysis of individual data.Systematic review registration: PROSPERO (ID: CRD42022382050)

Germination, growth and physiological responses of Senegalia senegal (L.) Britton, Vachellia seyal (Delile) P. Hurter and Prosopis juliflora (Swartz) DC to salinity stress in greenhouse conditions

Salinity is among the most widespread environmental threats to global plant  production, especially in arid and semi-arid climates. Thus, the selection of salt tolerant species is necessary for sustainable plant productivity. The purpose of this study was to measure and understand the salt tolerance of three multipurpose trees used in reforestation programs in many Sahelian countries (Senegalia senegal, Syn. Acacia senegal; Vachellia seyal, Syn. A. seyal, and Prosopis juliflora). The effect of salinity was evaluated at seed germination stage on Petri dishes containing water agar (0.9%, w/v) with seven concentrations of NaCl (0, 86, 171, 257, 342, 428, and 514 mM). Our results showed that all the species had a germination rate higher than 85% at 257 mM. However, it decreased at 342 mM with a reduction of 70 and 20%, respectively for S. senegal and V. seyal. For plants growth and physiological responses, seedlings were individually cultivated in plastic bags (25×12 cm) containing non-sterile soil and watered with four salt solutions (0, 86, 171 and 257 mM NaCl). Four months after the plants’ cultivation, the results showed that for all species, the salinity reduced significantly the height, the collar diameter, the shoot and root dry biomass as well as the total chlorophyll, K+ and K+/Na+ ratio. In the meantime, proline content, Cl- and Na+ accumulation in leaves were increased. It was also found that S. senegal and V. seyal tolerated high concentrations of NaCl (257 mM) and developed physiological and  molecular mechanisms, such as salt tolerance genes (NHX1), which allow them to be considered as moderated salt tolerant species and seemed to be potential species for the restoration of salt-affected land as P. juliflora.Key words: Multipurpose leguminous trees, abiotic stress, salt tolerance, Senegal

The Geographical Study of Anopheline Densities on a Small Space, using Satellite Imagery and Geographical Information Systems

International audienceTo predict the spatial distribution of anopheles in the Dielmo village (located in the southeastern part of Senegal), we used residual fauna collected from 104 different rooms during four separate trips conducted in 1994 and 1995. Thanks Generalized Estimating Equations, we were able to identify factors influencing the distribution of Anopheles in the village. Several variables, such as the number of persons sleeping in the room, population density around the hut, construction materials, presence of mosquito nets, were found to be significant, while many spatial variables relevant to the scale of a region (vegetation index, distance to larval sites...) were not found to be significant on the village level. As a result, it became clear that it is difficult to correctly predict the anopheline density for each house even with precise spatial data created with Satellite imagery and Geographical Information Systems (GIS). This work highlights the complexity of the geographical study of anopheline density and its limits on a small space

The Geographical Study of Anopheline Densities on a Small Space, using Satellite Imagery and Geographical Information Systems

International audienceTo predict the spatial distribution of anopheles in the Dielmo village (located in the southeastern part of Senegal), we used residual fauna collected from 104 different rooms during four separate trips conducted in 1994 and 1995. Thanks Generalized Estimating Equations, we were able to identify factors influencing the distribution of Anopheles in the village. Several variables, such as the number of persons sleeping in the room, population density around the hut, construction materials, presence of mosquito nets, were found to be significant, while many spatial variables relevant to the scale of a region (vegetation index, distance to larval sites...) were not found to be significant on the village level. As a result, it became clear that it is difficult to correctly predict the anopheline density for each house even with precise spatial data created with Satellite imagery and Geographical Information Systems (GIS). This work highlights the complexity of the geographical study of anopheline density and its limits on a small space

A Case of Visceral Leishmaniasis in a 4-Year-Old Child Living in Nonendemic Area Located in Suburbs of Dakar, Senegal

Visceral leishmaniasis (VL) is an infectious disease caused by protozoa of the genus Leishmania. Sporadic cases are observed in nonendemic areas and often associated with limited foci; therefore, the disease is easily overlooked. In addition, other diseases have similar clinical symptoms, which make it difficult for clinicians to make an accurate diagnosis and to provide effective treatment. We identified visceral leishmaniasis in a 4-year-old child in Pikine, Senegal. The patient was admitted to the Pikine National Teaching Hospital for haemorrhagic, tumoral, and infectious syndromes. At admission, the patient presented with epistaxis and gingivorrhagia, a severe anaemic syndrome poorly tolerated, a systemic inflammatory response syndrome with fever at 39.5°C, a tumoral syndrome with 11 cm of hepatomegaly and 12 cm of type IV splenomegaly, and noninflammatory macropoly adenopathies. A spinal cord puncture was performed, and direct microscopy examination of the sample after GIEMSA staining revealed amastigote forms of Leishmania. The PCR amplification of extracted DNA from the bone marrow aspiration using specific primers for VL (forward and reverse) confirmed that VL was responsible for the infection. A treatment with meglumine antimoniate (Glucantime) was given and it gave a successful outcome with remission of clinical symptoms and favourable evolution with 3 months hindsight. Conclusion. This visceral leishmaniasis case diagnosis in Senegal has shown that, apart from haematological malignancies, this disease must be considered in combination with a tumor syndrome, haemorrhagic syndrome, and infectious syndrome