South Cameroon Research Articles

Patterns of microbiome composition in tsetse fly Glossina palpalis palpalis during vector control using Tiny Targets in Campo, South Cameroon.

Novel vector control tools against African trypanosomiases require a deep understanding of the factors driving tsetse vector fitness or population resilience in their ecosystems. Following evidence of microbiota-mediated host fitness or traits shaping, including insecticide resistance in arthropod populations, we undertook a comparative study of the microbiota in wild-caught tsetse flies during vector control with deltamethrin-impregnated traps called Tiny Targets. The bacterial microbiome composition of tsetse flies collected before and after 6, 12, and 18 months of vector control were characterized using high-throughput sequencing of the V3-V4 hypervariable region of the bacterial 16S rRNA gene and compared. Overall, 48 bacterial genera and five phyla were identified. The primary symbiont Wigglesworthia dominated almost all the samples with an overall relative abundance of 71.76%. A significant increase was observed in microbiome diversities over the vector control with new taxa identified. Interestingly, few genera, like Curvibacter for instance, displayed a regularly increasing abundance, from 0.57% to 0.65%, 4.73%, and 8.57% after 6, 12, and 18 months of tsetse control, respectively. This study provided preliminary for further investigation into the role and mechanism of action of microbiota in tsetse fly fitness under selective pressure like insecticides.IMPORTANCEThe interest in vector control in the fight against African trypanosomiases has been reinforced in recent years, with the development of small insecticide-impregnated screens, known as "Tiny Targets". As some tsetse biotopes are difficult to access for their installation, other tools are under consideration that involve using bacteria harbored by the tsetse vector to block the development of trypanosomes or impair the tsetse's fitness in its natural environment. Several bacterial symbionts were previously described as important for tsetse fly development, and some like Burkholderia and Citrobacter also found in tsetse flies were found associated with insecticide tolerance in other arthropods. In this research, we found the bacterial genera, Curvibacter and Acinetobacter, increased in abundance in tsetse flies during vector control. These bacteria deserve further attention to determine if they can interfere with insecticides used to control tsetse fly populations.

The Limits of Archaeology and Cultural Anthropology: Archaeological Witnesses and Ethnographical Data Among the Bakola-Bagyeli “Pygmies” (South Cameroon)

The reading of the transformations recorded in the material equipment of disappeared societies still remains largely inspired by the dogma of materialism. This inclines inferences, in archaeology, to systematically deduce evolutionary stages on a double level, chronological and economic, from the material remains of technological changes only. However, the unpredictable experience of human societies can often reveal situations that contradict the established inferential model. Such a reality therefore poses the problem of searching for an approach capable of achieving balance in the possible equation between the experience of human societies and the methodological means implemented to account for it. The question therefore remains to know whether data collected and explained in a methodological approach specific to a discipline always reproduce the improbable nature of the reality of human societies, both living and extinct? Thus, ethnographic, qualitative data and archaeological facts are do they still agree regarding the current experience of life of the Bakola-Bayéli “Pygmies” of South Cameroon, since the 1990s? The hypothesis supports: data collected according to the orthodoxy of techniques specific to dissociated disciplinary fields, in a conventional manner, can contradict each other on the same fact. The complexity of the reality of human societies escapes the specific filter of conceptual and methodological practices characteristic of the disciplines that separate techniques specific to each method. The archaeological witnesses, taken from surveys carried out on the sites where the Bakola-Bagyéli “Pygmies” live, contradict the oral testimonies, given by these same populations through interviews, directive and semi-directive, guided by a questionnaire. A comparative study of qualitative and quantitative data makes it possible to verify the hypotheses put forward. The theoretical approach acquired to the cause of disorganization and opposed to the terminism of ends makes it possible to discuss the a priori organization of cultural facts and the accomplishment of reserved goals.

A Scoping Review of Stigma Related to Prostate Cancer in Black Men.

Prostate cancer (CaP) disproportionately affects 1-in-4 Black men and is a stigmatised disease within their communities. Yet, Black men are underrepresented in CaP research concerning stigma, which necessitates a scoping review to map available evidence on this topic to inform future research. To map published literature on stigma related to CaP in Black men to understand their experiences and/or perceptions and identify directions for future research. A scoping review was conducted using the five-step framework by Arksey and O'Malley. Studies published in English addressing stigma related to CaP from the perspectives of Black men and/or their families were included. We searched six databases including Medline, Embase, PsycInfo, CINAHL, Web of Science Core Collection and Google Scholar, from inception to April 2023. Citation searches were also conducted. Two independent reviewers conducted screening and data extraction. Data was synthesised using descriptive content analysis. Thirty-four eligible studies conducted in the USA, UK, Trinidad and Tobago, South Africa, Cameroon and Canada from 1995 to 2023 were included. A total of 1867 Black men with/without a CaP diagnosis and 145 adult partners were included. Review findings showed a complex intersection of self-stigma, public stigma and structural stigma impacted Black men's perceptions of their masculinity. While men's experiences/perceptions of stigma varied depending on their illness status, there were commonalities in their masculinity concerns (underpinned by stigma), which influenced their attitude towards digital rectal examination, post-treatment side effects and social interactions on CaP. These have implications for public health messaging on CaP within Black communities, as well as patient-provider interactions with the men. This novel review highlights the need to pay attention to how CaP is presented to Black men and their communities using avenues and languages that are culturally acceptable and empower them to negotiate self-stigma, public stigma and structural stigma related to CaP. Directions for further research were also identified.

Geochemistry of sand along the coastal beaches of the Mundeck formation and River Ntem, south Cameroon

Geochemistry of sand along the coastal beaches of the Mundeck formation and River Ntem, south Cameroon

Estimating groundwater resources in an equatorial forested basin using geographic information system and remote sensing techniques (case of Nyong, South Cameroon)

ABSTRACT This article aims to produce a groundwater potential zone (GWPZ) map of the Nyong basin using an integrated analytical hierarchy process driven in a geographic information system (GIS) environment. For this, seven parameters (rainfall, geology, slopes, drainage density, land use and land cover, lineament density, and soil) known to influence the availability of groundwater were considered. The results obtained show that the Eastern part of the basin holds the largest quantities of groundwater. The produced map shows that this region includes high and very high GWPZs (yield > 6 l/s). It is essentially characterized by abundant rainfall (on average 135–136 and 131–134 mm), low slopes, significant drainage and lineament densities, and significant forest cover. On the other hand, the opposite region (west), which includes the low and very low GWPZs, is characterized by less abundant precipitation (on average 121–125 and 125–128 mm), significant slopes, lower drainage and lineament densities, and greater impervious areas. With a success rate of 80%, confidence deserves to be placed in the GWPZs map produced. It can be considered in water supply projects in this basin. Such work has never been done in this basin before.

Optimisation of analytical methods for tuberculosis drug detection in wastewater: A multinational study

Wastewater-based epidemiology (WBE) is a robust tool for disease surveillance and monitoring of pharmaceutical consumption. However, monitoring tuberculosis (TB) drug consumption faces challenges due to limited data availability. This study aimed to optimise methods for detecting TB drugs in treated and untreated wastewater from four African countries: South Africa, Nigeria, Kenya, and Cameroon. The limit of detection (LOD) for these drugs ranged from a minimum of 2.20 (±1.02) for rifampicin to a maximum of 2.95 (±0.79) for pyrazinamide. A parallel trend was observed concerning the limit of quantification (LOQ), with rifampicin reporting the lowest average LOQ of 7.33 (±3.44) and pyrazinamide showing the highest average LOQ of 9.81 (±2.64). The variance in LOD and LOQ values could be attributed to factors such as drug polarity. Erythromycin and rifampicin exhibited moderately polar LogP values (2.6 and 2.95), indicating higher lipid affinity and lower water affinity.Conversely, ethambutol, pyrazinamide, and isoniazid displayed polar LogP values (−0.059, −0.6, and −0.7), suggesting lower lipid affinity and greater water affinity. The study revealed that storing wastewater samples for up to 5 days did not result in significant drug concentration loss, with concentration reduction remaining below 1 log throughout the storage period. Application of the optimised method for drug detection and quantification in both treated and untreated wastewater unveiled varied results. Detection frequencies varied among drugs, with ethambutol consistently most detected, while pyrazinamide and isoniazid were least detected in wastewater from only two countries. Most untreated wastewater samples had undetectable drug concentrations, ranging from 1.21 ng/mL for erythromycin to 54.61 ng/mL for isoniazid. This variability may suggest differences in drug consumption within connected communities. In treated wastewater samples, detectable drug concentrations ranged from 1.27 ng/mL for isoniazid to 10.20 ng/mL for ethambutol. Wastewater treatment plants exhibited variable removal efficiencies for different drugs, emphasising the need for further optimisation. Detecting these drugs in treated wastewater suggests potential surface water contamination and subsequent risks of human exposure, underscoring continued research's importance.

Petrological features of laterites developed on gneiss in the Mandoga area (south Cameroon plateau): evidence of two continuously differentiating pedodynamic domains

Petrological features of laterites developed on gneiss in the Mandoga area (south Cameroon plateau): evidence of two continuously differentiating pedodynamic domains

Characterization of heavy minerals and stream sediment from Bidjouka area, Nyong Complex south Cameroon: implications for gold mineralization

The stream sediment geochemistry has a wide application in mineral exploration. In this study, we applied the stream sediment geochemistry to decipher the primary source of gold mineralization, determine the mineralogy of heavy mineral concentrate and also to ascertain the provenance, depositional environment, intensity of weathering as well as determine the tectonic setting. To investigate heavy mineral in stream channel, 20 placer materials from Bidjouka area were assessed by thin plate using polarized microscope. The powder was further characterized by ICP-MS using aqua regia. Results show that placers displayed minerals such as magnetite, zircon and gold. Majors geochemical base metal point out low grade of iron (< 5 wt.%), titanium (< 1.05 wt.%) and alumina (< 0.60 wt.%). The following metallic trace elements used for industrial technology are identified in the samples. It mainly concerns manganese and thorium with content less than 328 and 200 ppm respectively as well as mercury (< 550 ppb). Precious metals are also present in the chemical composition of Bidjouka sediments. The main substances identified is gold with the grade above 2 g/tone, which is an important target in mining exploration. Also the mean value of rare earth elements varying between 1256.6 and 3626.8 ppm are so speculative, with negative and positive Eu and Ce anomaly respectively. Gold is bound with sulfide mineral (Au-Bi), suggesting a sulfidation event during sediments deposition. Factor 4 (Co, Mn, Sc, Au, Bi) refers to the mineralization factor and Co, Mn, Sc, Bi serve as pathfinder of gold. Sediments were deposited under humid, oxic and oxidizing conditions; intermediate intensity of weathering processes of the source rocks had prevailed during deposition, and sediments were rich in plagioclase. These continental sediments have quartzose sedimentary provenance, they were originated from metamorphic sources and were deposited in an active continental margin. The results of this study serve as guide for gold exploration and exploitation in the Bidjouka area.

Weight loss and mortality in people living with HIV: a systematic review and meta-analysis

BackgroundIn the first reported cases of human immunodeficiency virus (HIV) infection, people living with HIV (PLHIV) suffered weight loss, which was an independent predictor of mortality. Highly active antiretroviral therapy (HAART) has changed this scenario for ideal weight, overweight, and even obesity. However, some PLHIV, even on HAART, continue to lose weight. Thus, the guiding question of the study was: do PLHIV hospitalized using HAART with weight loss have higher mortality than hospitalized PLHIV using HAART without weight loss?MethodA systematic review and meta-analysis of prospective cohort studies published in English, Spanish, or Portuguese, searched in the MedLine, Embase, and LILACS databases from March 2020, until October 2023, reported by MOOSE. We analyzed the methodological quality and risk of bias using the Joanna Briggs Institute Critical Appraisal Tool for Cohort Studies; used the risk ratio (RR) to calculate the probability of hospitalized PLWH who lost weight dying, applied the random effect model and created the funnel plot. We used the inverse variance test estimated by the Mantel-Haenszel method, considering a 95% confidence interval (CI), heterogeneity (I2), total effect size (Z), and significance value of p < 0.05. We performed a sensitivity analysis with meta-regression and meta-analyses on subgroups to diagnose influence and outliers. The quality of evidence and strength of recommendation were analyzed using the Grading of Recommendations Assessment, Development, and Evaluation system (GRADE).ResultsWe included 10 of the 711 studies identified, totaling 1,637 PLHIV. The studies were from South Africa (1), Canada (1), China (1), Brazil (1), Cameroon (1), Ethiopia (1), Thailand (1), Colombia (1), and Tanzania (2), from 1996 to 2017. The average age of the participants was 33.1 years old, and the male was predominant. The leading causes of hospital admission were related to co-infections, and the average hospitalization time was 20.5 days. The prevalence of death in hospitalized PLHIV using HAART who lost weight was 57.5%, with a 1.5 higher risk of dying (RR: 1.50, 95% CI: 1.03, 2.19, p = 0.04) than hospitalized PLHIV who did not lose weight.ConclusionWe concluded, with a very low confidence level, that that weight loss significantly increased the risk of death in hospitalized PLWH using HAART.Trial Registration and fundingPROSPERO International Prospective Register of Systematic Reviews CRD42020191246 https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020191246.

Prevalence and zoonotic risk factors of Mycobacterium bovis tuberculosis in cattle at the cattle-wildlife-human interface in South and East Cameroon.

Bovine tuberculosis (bTB) is a contagious and notifiable disease, which is prevalent in cattle populations of many countries and in several wildlife species worldwide. However, the role of wildlife in the transmission and/or maintenance of bTB at the human-wild animal-animal interface and the epidemiology of zoonotic disease are poorly understood in Cameroon, where many wildlife species exist. This study aimed to estimate the prevalence and zoonotic risk factors of bTB at the cattle-wildlife-human interface in the South and East regions of Cameroon. We conducted a descriptive cross-sectional study from May to October 2022 in the southern region (Vallée du Ntem and Dja et Lobo) and eastern region (Haut Nyong and Lom et Djérem) of Cameroon to determine risk factors for bTB in Zebu Bororo, Goudali, Ndama, and Simmental cattle breeds. A comparative intradermal tuberculin testing (CIDT) was performed on 160 cattle randomly selected from herds using the threshold recommended by the World Organization for Animal Health. An interviewee-administered questionnaire was used to gather epidemiological data on sociodemographics, interaction between cattle and wildlife, and awareness of zoonotic tuberculosis (TB) from 90 cattle professionals. The prevalence of bTB at the herd level and associated risk factors were estimated using multiple logistic regression models. Based on the comparative intradermal tuberculin test (CIDT), the estimated prevalence of bTB in 160 cattle (Zebu Bororo, Goudali, Ndama, and Simmental) in South and East Cameroon was 6.8% (4.35%-9.41%) and 1.8% (0%-3.6%) for threshold values 3 mm and 4 mm, respectively. The prevalence obtained by simple intradermal tuberculin test (IDT) was 0.6% (0%-1.2%) for a threshold value 4 mm. Univariate analysis revealed three risk factors associated with bTB with significant odds ratios (OR; p = 0.05): herd size (OR = 4.88; 95% confidence interval [CI]: 1.24-32.56); cattle aged>10 years (OR = 0.17; 95% CI: 0.05-0.53); and victims of bTB organ seizure (OR = 0.015; 95% CI: 0.002-0.067). Multivariate analysis showed that being a cattle herder and contact between wildlife and livestock due to forage was significantly associated with bTB exposure (adjusted OR = 0.02; p = 0.001). Bovine TB is prevalent in cattle of the South and East Cameroon. Comparative IDT of cattle reared in the epidemiological and environmental context of the study areas yielded better results at a threshold of 3 mm than at a threshold of 4 mm recommended by the World Health Organization. Factors associated with exposure to/appearance of bTB were high herd size, cattle aged >10 years old, seizures of tuberculous organs, shepherding as a profession, and contact between cattle and wildlife can be due to lack of forage.

3D depth estimation of Mingo’o’s iron mineralization from outcrop data and geophysical analysis (South Cameroon, northern edge of the Congo Craton)

3D depth estimation of Mingo’o’s iron mineralization from outcrop data and geophysical analysis (South Cameroon, northern edge of the Congo Craton)

A systematic review and meta-analysis on outcomes ofvalvular heart surgery in Africa.

The prevalence of valvular heart diseases remain considerably high in Africa, largely but not solely due to rheumatic heart disease. Valvular heart surgeries have emerged as the cornerstone in their management. While several studies have reported data on outcomes following heart valve surgery in many developed countries, there is a staggering paucity of data and evidence reporting the outcomes in the Africa population. The aim of this study is to report the perioperative outcomes following valvular heart surgery in Africa. The Preferred Reporting Items for Systematic Reviews and Meta-analysis guideline was utilized. Electronic searches were performed using PubMed, African journal online, and Research gate from inception to June 2023. The primary endpoints were overall mortality and 30-day mortality, and secondary endpoints included postoperative complications, length of hospital, and intensive care stays. The outcome data were pooled together and analyzed with the random effect model for proportions and mean for meta-analysis using the R software. This systematic review identified 31 studies that fulfilled the study eligibility criteria and all were observational studies. The countries in which these studies were carried out include South Africa, Ethiopia, Egypt, Mali, Rwanda, Nigeria, Cameroon, Ghana, Senegal, Tanzania, and Kenya. Statistical analysis reported a pooled overall mortality of 10.48% and a pooled 30-day mortality of 4.59%. Several obstacles, such as lack of financial resources and inadequate infrastructure, continue to impede valvular heart surgery practice in many parts of Africa. Future studies need to focus on identifying factors associated with this poor early mortality.

Impact of a small-scale tsetse fly control operation with deltamethrin impregnated "Tiny Targets" on tsetse density and trypanosomes' circulation in the Campo sleeping sickness focus of South Cameroon.

Significant progress has been made towards African sleeping sickness elimination in the last decade. Indeed, the World Health Organization (WHO) global goal of eliminating the chronic form of the disease as a public health problem was achieved in 2020 (i.e., < 2,000 new cases per year). Vector control has played an important role in achieving this goal. In this study, we evaluated the impact of the insecticide impregnated Tiny Targets on tsetse fly densities and their infection rates with Trypanosoma spp in the Campo sleeping sickness focus of South Cameroon. The study site was divided into two areas: (i) the south-west experimental area, which included vector control, and (ii) the eastern part as the non-intervention area. After compiling the baseline entomological data (tsetse densities and trypanosome infection rates), around 2000 Tiny Targets were deployed in the South-West area and replaced every six months for two years. Post-intervention surveys were conducted every six months to determine tsetse densities and levels of trypanosome infections with PCR-based methods. Following the intervention, tsetse mean catches decreased by 61% after six months, and up to 73% after twelve months (pre-intervention: 2.48 flies/trap/day, 95%CI [1.92-3.14]; 12-months post-intervention: 0.66 tsetse/trap/day, 95%CI [0.42-0.94]). This decrease was not sustained after 18 months, and the mean catch doubled compared to that after 12 months. After 24 months, the mean catches still increased by 17% (18 months: 1.45 tsetse/trap/day, 95%CI [1.07-1.90] and 24 months: 1.71 tsetse/trap/day, 95%CI [1.27-2.24]). In the non-intervention area, a variation in tsetse catches was observed during the two years, with a general increase from 2.43 [0.73-5.77] to 3.64 [1.47-7.70] tsetse/trap/day. In addition, trypanosome infection rates dropped by 75% in both areas (P-value < 0.001) from 21.20% to 5.06% and from 13.14% to 3.45% in intervention and control areas respectively. Tiny targets have proven useful in reducing tsetse population densities and trypanosome infection rates, providing evidence for the integration of this tool in current strategies towards trypanosomiasis elimination in Campo. The non-sustained decrease of tsetse densities after one year may indicate reinvasions from neighbouring breeding sites or that the intervention area was not large enough. Our results show the need to scale up by accessing difficult breeding sites and extend the tiny targets to the whole transborder focus.

The political economy of political corruption in 21st century Africa: Perspectives from Cameroon and South Africa

AAFrom ancient to modern times, corruption has plagued human civilisation. Its existence confirms that it has been integrated into the social fabric of global society and become a vice of governance. Corruption has dual implications: the direct financial benefit for the perpetrators due to the misuse of entrusted power, which raises the issue of accountability; and the deprivation to society of the allocation of resources. Political corruption results in large amounts of public funds being systematically siphoned off at the expense of society, and against the dictates of the constitutional values of transparency and accountability. For South Africa and Cameroon, political corruption continues to impede growth and development, despite the prevalence of anti-corruption mechanisms in these countries. From a comparative perspective, we investigate the scale and consequence of political corruption in South Africa and Cameroon to analyse the existing anti-corruption mechanisms, strategies and regimes in the two countries in combatting political corruption. We further analyse how and to what extent courts, particularly the Special Crime Court in Cameroon, have been able to address the issue. Furthermore, we demonstrate the similarities between high-level abuse of power in South Africa and Cameroon, notwithstanding existing anticorruption mechanisms. We conclude that a proactive system of checks and balances is urgently required to quench the growing cancerous phenomenon of political corruption in Africa, specifically in Cameroon and South Africa.

The Fang-Bulu-Beti (1665-1850): origin and migrations in Central Africa

This research seeks to determine the starting point of the Fang-Bulu-Beti migrations of Central Africa, from the savannah to the forest. Using new African historiography, it analyzes the three main theories of common savannah origin known about this people. The first theory refers to the area around Lake Chad while another refers to the Upper Sanaga area. Cross-reading of the relevant sources, spanning the period from 1819 to 2018 reveal that that the starting point of common dispersal of the Fang-Bulu-Beti in the forest was neither in the savannahs around Lake Chad, nor in the Upper Sanaga, but in the southern Adamawa region of Cameroon. Within the period of 1665, the Fang separated from the Bulu-Beti and left that place for the forest of South-Cameroon and Gabon through the current East-region. At that same moment, certain Beti people (the Enoa, Benë and Emburi) decided to live the southern Adamawa and passed through the Mbam area to reach the forest of the current Centre region of Cameroon. The other Beti-Bulu later left that savannah environment for Upper Sanaga and for the Centre and South regions of Cameroon. Several reasons could explain this abandonment: Invasion of newly arrived people (Baare-Tchamba and Baya), some inner quarrels and the quest for enrichment towards the Atlantic coast of Kribi in the South Cameroon during 1840-1850 decade.

Evaluation by benthic macroinvertebrates of the state of health of some rivers in the south Cameroon region

Benthic macroinvertebrates are the best indicators of the ecological quality of watercourses because of their specific diversity, their sensitivity, their variable life span and their capacity to adapt to all types of environments. In order to determine the health status of some rivers in the Southern Cameroon Region, a study was conducted in Kribi in the Ocean Department between February 2022 and February 2023. Physicochemical analyses were carried out according to conventional methods. Sampling of benthic macroinvertebrates was done using the multihabitat approach. The results of physicochemical parameters revealed that the water courses were well oxygenated, with a slightly acidic pH with little disturbances from anthropic activities. The abundance of benthic macroinvertebrates showed 17055 individuals collected belonging to 2 phyla, 3 classes, 19 orders, 59 families and 113 genera. The class of Crustacea dominated with 7693 individuals or 45.10% of relative abundance, followed by Gastropods with 5174 individuals or 30.33% of relative abundance and Insects with 4188 individuals or 24.55% of relative abundance. The taxonomic diversity, coupled with the EPT, EPTD, EPTC and EPTH indices, revealed that the water from these water courses is of good ecological quality.

Geochemical balance of the mineral fraction and statistical analyzes of the Ebolowa municipal lake’s sediments (central Africa): Implication for early diagenesis process

The Ebolowa Municipal Lake (EML) (South Cameroon) in order to identify the early diagenesis processes taking place in the lake and the factors influencing them. To this end, 21 samples were collected. In situ, hydrogen potential, redox potential, conductivity, dissolved oxygen content, and turbidity were measured. In the laboratory, the samples were subjected to mineralogical analysis by X-ray diffraction, geochemical analysis by X-ray fluorescence and ICP-MS, and statistical analysis. The coefficient of variation (Qi) was calculated from the geochemical data. In the water column, OD > 2 mg/L, pH > 7 and Eh < 0 mV. In sediments: pH < 7, Eh values are lower. The contents of 2.08 ≤ TOC ≤ 12.65%. The mineralogical procession consists of quartz, kaolinite, gibbsite, goethite, and siderite. The latter is only present in the EML. The sediments are dominated by SiO2 (60.44–89.47%), Al2O3 (6.55–18.17%), and Fe2O3 (1.15–6.21%). The Qi values range from 0.73 to 2.31. The Mn/Fe ratio values are below 0.40. Qi > 1 for Al, Fe, Mn, Mg, K, Na, P, Ni, Co, Zn, Pb, Cd, Cu, Ba, and V, and Qi < 1 for Si; Qi = 1 for Ca. The hierarchical cluster analysis shows two groups: the first one includes the samples from the central and western parts, while the second one includes those from the eastern and southern parts of the lake. The water column is subject to oxic conditions, while the sediments are anoxic. The rapid consumption of oxygen is due to organic mineralization, which is the main diagenesis observed in the lake. This phenomenon is more accentuated in the western part of the lake.

Combined bulk-rock Lu-Hf and Sm-Nd isotopic study of Archean granitoids and mafic rocks from Sangmelima terranes (Ntem Complex, south Cameroon): Geodynamic implications

Hafnium and neodymium isotopes provide robust tool tracers for tracking the mechanisms of crustal generation and differentiation, from mantle extraction to the late geological processes undergone by the studied rocks. Though these two isotope systems commonly behave similarly and define a positive correlation between 143Nd/144Nd and 176Hf/177Hf referred to as the “terrestrial array”, they may differ in terrains having a complex geological history, such as Archean cratons. This study presents the first combined whole-rock Hf and Nd isotopic analyses of Archean mafic and felsic igneous rocks from the Sangmelima terranes in the Ntem Complex (located in the Northwest of Congo Craton (NW CC) in southern Cameroon). It mainly consists of Mesoarchean charnockites and tonalite-trondhjemite-granodiorite (TTG) suites, greenstone belts, mafic enclaves or dykes, and potassic granitoids. Mesoarchean charnockite and TTG suites have subchondritic initial 176Hf/177Hf and 143Nd/144Nd ratios with a mean initial (suffix (i)) ε176Hf(i) and ɛ143Nd(i) of –3.30 ± 1.40 and –3.85 ± 0.65 (2SD) respectively, implying the involvement of Eo- to Paleoarchean components in their petrogenesis. The bulk rock initial Hf and Nd isotope compositions of the gabbro and gabbronorites are suprachondritic (ε176Hf(i) = +3.4 to + 8.2; ε143Nd(i) = +0.9 to + 1.6), indicate that they were derived from a depleted mantle source. Coupled with pre-existing data from the literature, these new Hf-Nd isotopic data indicate that two episodes of mantle-derived mafic magmatism in the Ntem Complex occurred during the Mesoarchean period (i.e., at ∼ 3.1 and 2.86 billion years (Ga)). Neoarchean dolerite dykes show broadly chondritic to supra-chondritic ε176Hf(i) and ε143Nd(i) values of –0.28 to + 4.53 and TCHUR ages of 2.74 – 2.76 Ga, suggesting the derivation of doleritic magma from a depleted mantle source with either none or limited crustal residence time. Considering other Archean domains of the NW CC, there were multi-stage magmatism events and crustal growth events occurred at ∼3.75 – 3.31 Ga, ∼3.26 – 3.0 Ga, ∼2.92 – 2.85 Ga, and ∼2.75 – 2.72 Ga from Eoarchean to Neoarchean in the NW Congo Craton.

African care for congenital central nervous system disorders: Falling far short of global management standards?

African care for congenital central nervous system disorders: Falling far short of global management standards?

Assessment of the Insect pests of flowers and fruits diseases impact on the Solo papaya in a field of Meyomessala locality, South region Cameroon

Assessment of the Insect pests of flowers and fruits diseases impact on the Solo papaya in a field of Meyomessala locality, South region Cameroon