Institute Of Recherche Agricole Pour Le Developpement

Ngaoundéré, Cameroon

Institute Of Recherche Agricole Pour Le Developpement

Ngaoundéré, Cameroon
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Bah G.S.,University of Liverpool | Bah G.S.,Institute Of Recherche Agricole Pour Le Developpement | Ward E.L.,University of Liverpool | Trees A.J.,University of Liverpool | And 2 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2014

Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a major cause of visual impairment and dermatitis in sub-Saharan Africa. As O. volvulus contains an obligatory bacterial symbiont (Wolbachia), it is susceptible to antibiotic chemotherapy, although current regimens are considered too prolonged for community-level control programs. The aim of this study was to compare the efficacies of oxytetracycline and rifampin, administered separately or in combination, against a close relative of O. volvulus (Onchocerca ochengi) in cattle. Six animals per group were treated with continuous or intermittent oxytetracycline regimens, and effects on adult worm viability, dermal microfilarial loads, and Wolbachia density in worm tissues were assessed. Subsequently, the efficacies of 3-week regimens of oxytetracycline and rifampin alone and a combination regimen were compared, and rifampin levels in plasma and skin were quantified. A 6-month regimen of oxytetracycline with monthly dosing was strongly adulticidal, while 3-week and 6-week regimens exhibited weaker adulticidal effects. However, all three regimens achieved>2-log reductions in microfilarial load. In contrast, rifampin monotherapy and oxytetracycline-rifampin duotherapy failed to induce substantive reductions in either adult worm burden or microfilarial load, although a borderline effect on Wolbachia density was observed following duotherapy. Dermal rifampin levels were maintained above the MIC for>24 h after a single intravenous dose. We conclude that oxytetracycline-rifampin duotherapy is less efficacious against O. ochengi than oxytetracycline alone. Further studies will be required to determine whether rifampin reduces oxytetracycline bioavailability in this system, as suggested by human studies using other tetracycline-rifampin combinations. Copyright © 2014, American Society for Microbiology. All Rights Reserved.


Grant
Agency: European Commission | Branch: FP7 | Program: CSA-CA | Phase: KBBE-2007-1-2-12 | Award Amount: 1.22M | Year: 2008

The project concept is to build a sustainable aquaculture research network based on academics and other professionals between Europe and Africa, with a focus on Sub-Saharan Africa. The three-year work plan will strengthen alliances among experienced and emergent players in the African and wider aquaculture scene that will build on an existing framework knowledge resource base and exchange platform - the Aquaculture Compendium. Project partners: Institute of Aquaculture, University of Stirling (coordinator; UK); CIRAD (France); WorldFish Center (Egypt), CABI (UK HQ); Asian Institute of Technology (Thailand), Bunda College of Agriculture (Malawi); IRAD (Cameroon); and ETC (Netherlands). This consortium has a balance of expertise in aquaculture research, development and policy information technology; ability to work in different linguistic areas; and a track record in the implementation of activities at local to international levels. The project will work across a wide range of stakeholders (researchers, SMEs, government agencies, NGOs, producers and others) throughout Sub-Saharan Africa; between anglophone and francophone regions in Africa; between Africa and Asia; and between Europe and Africa. In 6 Work Packages, the project will deliver (1) the comprehensive interdisciplinary knowledge base required for Sub-Saharan African aquaculture to develop in a sustainable way; (2) a sustainable process to identify and nurture new initiatives for Sub-Saharan African aquaculture research, with key involvement of European stakeholders; (3) learning and adaptation for Sub-Saharan Africa of the processes of aquaculture researchinto-practice through multi-stakeholder collaboration of research-to-practice networks developed in Southeast Asia; (4) maximal dissemination of project outputs; and (5) tools to aid policy-making for aquaculture in Africa. Mechanisms will be in place by the project end to enable sustainability of the networks established during the project.


Grant
Agency: European Commission | Branch: FP7 | Program: CP-SICA | Phase: ENV.2008.1.1.5.1. | Award Amount: 4.77M | Year: 2009

The proposal addresses Topic ENV.2008.1.1.5.1 Addressing deforestation in tropical areas: greenhouse gas emissions, socio-economic drivers and impacts, and policy options for emissions reduction. The overall goal of the project is to contribute to the development and evaluation of mechanisms and the institutions needed at multiple levels for changing stakeholder behaviour to slow tropical deforestation rates and hence reduce GHG emissions. This will be achieved through enhancing our understanding of the social, cultural, economic and ecological drivers of forest transition in selected case study areas in Southeast Asia, Africa and South America. This understanding will facilitate the identification and assessment of viable policy options addressing the drivers of deforestation and their consistency with policy approaches on avoided deforestation, such as Reduced Emissions from Deforestation and degradation (REDD), currently being discussed in UNFCCC and other relevant international fora. At the same time, ways of improving the spatial quantification of land use change and the associated changes in GHG fluxes will be developed, thereby improving the accounting of GHG emissions resulting from land use change in tropical forest margins and peatlands. This will allow the analysis of scenarios of the local impacts of potential international climate change policies on GHG emission reductions, land use, and livelihoods in selected case study areas, the results of which will be used to develop new negotiation support tools for use with stakeholders at international, national and local scales to explore a basket of options for incorporating REDD into post-2012 climate agreements. The project will provide a unique link between international policy-makers and stakeholders on the ground who will be required to change their behaviour regarding deforestation, thereby contributing to well-informed policy-making at the international level.


Grant
Agency: European Commission | Branch: FP7 | Program: CP-FP-SICA | Phase: HEALTH-2009-4.3.1-1 | Award Amount: 6.63M | Year: 2010

Filarial infections remain a major public health problem in West and Central Africa. Three filarial species are involved: Onchocerca volvulus (onchocerciasis or river blindness); Wuchereria bancrofti (lymphatic filariasis); and Loa loa (the eye worm). Treatment of onchocerciasis with ivermectin has been successful in many situations but emergence of drug resistance and risk of severe adverse reactions associated with L loa co-infections is restricting the implementation of mass treatment and consequently alternate approaches to control are required. Studies with animal models have identified the general mechanisms of protective immunity while human studies have drawn attention to immune regulatory processes that influence clinical presentations Together, these observation provide a basis for vaccine development. The next challenge is to identify target antigens and ensure appropriate formulation and delivery to promote protective responses and avoid any pathology. This project aims to: 1, use transciptomics and bioinformatics to identify the parasite molecules that are targets of protective immunity and that may influence the regulation of such responses; and 2, microarray technologies and bioinformatics to determine the pathways that lead to expression of protective immunity. Cohorts of onchocerciasis patients who have received treatment with ivermectin or tetracycline, or are co infected with either W bancrofti or L loa provide both input to the pathway studies and a means of validation of the computer assimilations. Confirmation of the mechanisms and targets of protective immunity and validation of computer assimilations will also be investigated using the O ochengi-cattle model that also enables experimentation under natural challenge. Litomosoides sigmodontis in mice provides a robust and rapid validation of results obtained from computation relating to expression and regulation of protective responses and a primary system for screening vaccine candidates


Lezine A.-M.,French National Center for Scientific Research | Assi-Kaudjhis C.,French National Center for Scientific Research | Assi-Kaudjhis C.,University of Liège | Roche E.,University of Liège | And 2 more authors.
Journal of Biogeography | Year: 2013

Aim: Our aims were to provide a detailed chronology of past vegetation changes in the tropical mountains of west-central Africa since the Last Glacial Maximum and to discuss montane forest responses to climate change in terms of distribution and biodiversity. Location: Lake Bambili, western Cameroon (05°56′ N, 10°14′ E, 2273 m a.s.l.). Methods: Fossil pollen was extracted from a long, continuous and well-dated sedimentary sequence extending back 20,000 years. Pollen diversity and evenness estimates were based on rarefaction analysis and on Simpson's (1/D) index. Results: Forest was nearly absent from high elevations during the last glacial period. It expanded gradually from 18.4 cal. kyr bp, interrupted only by reversals coincident with the Heinrich 1 (H1) and Younger Dryas (YD) climatic events, and then suddenly collapsed at 3.3 cal. kyr bp. This switch from forest to grassland communities occurred within a time span of three centuries. After 3.3 cal. kyr bp only short and taxon-poor forest phases are recorded, specifically between 2.7 and 1 cal. kyr bp and in recent centuries. Main conclusions: Our data indicate that the mountain forests of Cameroon are recent, resulting from plant migrations from various sources from 18.4 cal. kyr bp onwards. Their progressive development closely followed intensification of the Atlantic monsoon, leading to the formation of a dense forest between 11.7 and 3.3 cal. kyr bp. The composition of this forest included the co-occurrence of species whose ranges do not overlap today, and indicates the potential for the development of unique iterations of climax forests through time. These forests appear to be very sensitive to Northern Hemisphere climate change, with phases of expansion/contraction coeval with the boreal deglacial signal, including widely recognized events such as H1, the YD and the 8.2 ka event. From 8.2 cal. kyr bp onwards, the progressive opening of the canopy is likely to reflect increased seasonality in rainfall related to more frequent El Niño/Southern Oscillation (ENSO) events. The final step of this history was the collapse of the montane forest at 3.3 cal. kyr bp. During the last millennium, very severe disruptions have meant that only the most rapidly dispersing species could spread, contributing to a drastic loss of forest biodiversity that has been accentuated by human impact in the last few centuries. © 2012 Blackwell Publishing Ltd.


The taxonomy of Rutaceae-Toddalieae of Cameroon is revisited on the basis of fertile samples, images of specimens, and systematic literature. Species identification based on the correlation of morphological characters of leaves, inflorescences and fruits, let to recognize four new species including Vepris adamaouae Onana, sp. nov. with the lamina of the leaflets decurrent on the petiolule, slender inflorescences axes and stamens about twice as long as the petals; V. araliopsioides Onana, sp. nov., with 5-folilated leaves and foveolate fruit exocarp; V. letouzeyi Onana, sp. nov. with winged petioles, finely furrowed foveolate fruits exocarp; and V. montisbambutensis Onana, sp. nov. with smaller leaves and fruit compared to other species of the genus. Moreover the material distinguished by the petiolule reduced to a bulge might represent a new species, not yet validated because of the lack of mature flowers and fruits. Toddaliopsis ebolowensis (Engl.) Onana, comb. nov. is lectotypified, allowing the validation of the new combination V. ebolowensis (Engl.) Onana, comb. nov.. The true identity of Teclea campestris and Vepris tabouensis is proposed: they are conspecific with respectively V. heterophylla (Engl.) Letouzey and V. soyauxii (Engl.) Mziray. A key to distinguish species is proposed. New taxa and those with previously confused identification or taxonomic uncertain position are illustrated and their geographical distributions presented. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris.


Van Straaten O.,University of Gottingen | Corre M.D.,University of Gottingen | Wolf K.,University of Gottingen | Tchienkoua M.,Institute Of Recherche Agricole Pour Le Developpement | And 4 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

Tropical deforestation for the establishment of tree cash crop plantations causes significant alterations to soil organic carbon (SOC) dynamics. Despite this recognition, the current Intergovernmental Panel on Climate Change (IPCC) tier 1 method has a SOC change factor of 1 (no SOC loss) for conversion of forests to perennial tree crops, because of scarcity of SOC data. In this pantropic study, conducted in active deforestation regions of Indonesia, Cameroon, and Peru, we quantified the impact of forest conversion to oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), and cacao (Theobroma cacao) agroforestry plantations on SOC stocks within 3-m depth in deeply weathered mineral soils. We also investigated the underlying biophysical controls regulating SOC stock changes. Using a space-for-time substitution approach, we compared SOC stocks from paired forests (n = 32) and adjacent plantations (n = 54). Our study showed that deforestation for tree plantations decreased SOC stocks by up to 50%. The key variable that predicted SOC changes across plantations was the amount of SOC present in the forest before conversion-the higher the initial SOC, the higher the loss. Decreases in SOC stocks were most pronounced in the topsoil, although older plantations showed considerable SOC losses below 1-m depth. Our results suggest that (i) the IPCC tier 1 method should be revised from its current SOC change factor of 1 to 0.6 ± 0.1 for oil palm and cacao agroforestry plantations and 0.8 ± 0.3 for rubber plantations in the humid tropics; and (ii) land use management policies should protect natural forests on carbon-rich mineral soils to minimize SOC losses.


Koutsovoulos G.,University of Edinburgh | Makepeace B.,University of Liverpool | Tanya V.N.,Institute Of Recherche Agricole Pour Le Developpement | Blaxter M.,University of Edinburgh
PLoS Genetics | Year: 2014

Wolbachia are common endosymbionts of terrestrial arthropods, and are also found in nematodes: the animal-parasitic filaria, and the plant-parasite Radopholus similis. Lateral transfer of Wolbachia DNA to the host genome is common. We generated a draft genome sequence for the strongyloidean nematode parasite Dictyocaulus viviparus, the cattle lungworm. In the assembly, we identified nearly 1 Mb of sequence with similarity to Wolbachia. The fragments were unlikely to derive from a live Wolbachia infection: most were short, and the genes were disabled through inactivating mutations. Many fragments were co-assembled with definitively nematode-derived sequence. We found limited evidence of expression of the Wolbachia-derived genes. The D. viviparus Wolbachia genes were most similar to filarial strains and strains from the host-promiscuous clade F. We conclude that D. viviparus was infected by Wolbachia in the past, and that clade F-like symbionts may have been the source of filarial Wolbachia infections. © 2014 Koutsovoulos et al.


Darby A.C.,University of Liverpool | Armstrong S.D.,University of Liverpool | Bah G.S.,University of Liverpool | Bah G.S.,Institute Of Recherche Agricole Pour Le Developpement | And 12 more authors.
Genome Research | Year: 2012

The α-proteobacterium Wolbachia is probably the most prevalent, vertically transmitted symbiont on Earth. In contrast with its wide distribution in arthropods, Wolbachia is restricted to one family of animal-parasitic nematodes, the Onchocercidae. This includes filarial pathogens such as Onchocerca volvulus, the cause of human onchocerciasis, or river blindness. The symbiosis between filariae and Wolbachia is obligate, although the basis of this dependency is not fully understood. Previous studies suggested that Wolbachia may provision metabolites (e.g., haem, riboflavin, and nucleotides) and/or contribute to immune defense. Importantly, Wolbachia is restricted to somatic tissues in adult male worms, whereas females also harbor bacteria in the germline. We sought to characterize the nature of the symbiosis between Wolbachia and O. ochengi, a bovine parasite representing the closest relative of O. volvulus. First, we sequenced the complete genome of Wolbachia strain wOo, which revealed an inability to synthesize riboflavin de novo. Using RNA-seq, we also generated endobacterial transcriptomes from male soma and female germline. In the soma, transcripts for membrane transport and respiration were up-regulated, while the gonad exhibited enrichment for DNA replication and translation. The most abundant Wolbachia proteins, as determined by geLC-MS, included ligands for mammalian Toll-like receptors. Enzymes involved in nucleotide synthesis were dominant among metabolism-related proteins, whereas the haem biosynthetic pathway was poorly represented. We conclude that Wolbachia may have a mitochondrion-like function in the soma, generating ATP for its host. Moreover, the abundance of immunogenic proteins in wOo suggests a role in diverting the immune system toward an ineffective antibacterial response.


Hansen R.D.E.,University of Liverpool | Trees A.J.,University of Liverpool | Bah G.S.,Institute Of Recherche Agricole Pour Le Developpement | Hetzel U.,University of Liverpool | And 4 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

Onchocerca ochengi, a filarial parasite of cattle, represents the closest relative of the human pathogen, Onchocerca volvulus. Both species harbour Wolbachia endosymbionts and are remarkable in that adult female worms remain viable but sessile for many years while surrounded by host cells and antibodies. The basis of the symbiosis between filariae and Wolbachia is thought to be metabolic, although a role for Wolbachia in immune evasion has received little attention. Neutrophils are attracted to Wolbachia, but following antibiotic chemotherapy they are replaced by eosinophils that degranulate on the worm cuticle. However, it is unclear whether the eosinophils are involved in parasite killing or if they are attracted secondarily to dying worms. In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine. In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability. Eosinophil degranulation increased significantly only in the oxytetracycline group; whereas nodular gene expression of bovine neutrophilic chemokines was lowest in this group. Moreover, intense eosinophil degranulation was initially associated with worm vitality, not degeneration. Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response. © 2010 The Royal Society.

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