Joseph Amang A Mbang

Dynamics of Powdery Mildew Transmission in Cashew Plants Under Lévy Noise: A Nonlinear Stochastic Model

Albert Kouchéré Guidzavaï, Hamadjam Abboubakar, Joseph Mbang, Rashid Jan

Axioms

Powdery Mildew is a global plant disease caused by fungal species, causing powdery growth on various parts of plants. This study aims to develop, evaluate and simulate the transmission dynamics of Powdery Mildew in cashew plants using a stochastic differential equation with Lévy noise. After providing some preliminary definitions of stochastic differential equations, we first consider the model without noise. We prove positivity, compute the basic reproduction number, R0, the PMD-free equilibrium, and the existence of a unique endemic equilibrium point whenever R0>1. After that, we formulate the stochastic model under Lévy noise. For this model, we also prove the positivity of the solutions and show that it is possible to extend the disease when Ss<1. We also found the condition that ensures the persistence of the disease if S0s>1. To simulate the model, we build a stochastic model numerical scheme and do a number of numerical simulations to support the theoretical findings we have gotten.

• #powdery mildew fungal diseases
• #fungal plant pathogen control
• #plant pathogens and resistance
• #powdery mildew

CTL Inclusive HIV-1 Infection Model with Nonlocal Diffusion Process, Intracellular Delays and Spatial Heterogeneity

Yannick -L. Djeunankam, M Mann-Manyombe, Denis F. Nkoa-Onana, Joseph Mbang

Differential Equations and Dynamical Systems

• #mathematical and theoretical epidemiology and ecology models
• #mathematical biology tumor growth
• #covid-19 epidemiological studies
• #ctl*

Dynamics of a nonlocal diffusion model of hepatitis C virus infection with logistic hepatocyte growth and spatial heterogeneity

Armel Willy Tacteu Fokam, Alexis Nangue, Joseph Mbang

International Journal of Biomathematics

In this work, a nonlocal diffusion viral infection within-host model with logistic hepatocyte growth is analyzed. The latter takes into account absorption effect and the usage of the standard incidence force for viral infection in a spatially heterogeneous environment. We first establish the well-posedness, boundedness and asymptotic smoothness of this model. Furthermore, the perturbation technique has enabled us to define the basic reproduction number [Formula: see text] and a threshold [Formula: see text] such that if [Formula: see text], the infection-free equilibrium is globally asymptotically stable. Next, we show that the model is uniformly persistent when [Formula: see text]. Finally, we present some numerical simulations to confirm our obtained theoretical results.

• #mathematical and theoretical epidemiology and ecology models
• #hepatitis c virus research
• #dynamics (music)
• #spatial heterogeneity

Existence solutions for nondensely integrodifferential equations with state-dependent delay

Moussa El-Khalil Kpoumiè, Yannick-Levis Djeunankam, Joseph Mbang, Pierre Noundjeu

Asian-European Journal of Mathematics

In this work, we study the existence of mild solutions for some nondensely partial functional integro-differential equations with state-dependent delay in Banach spaces. We assume that the linear part is not necessarily densely defined and generates an integrated resolvant operators. The nonlinear part satisfies Carathéodory’s conditions. Our approach is based on the generalized Darbo Fixed Point Theorem on Banach spaces and the integrated resolvent operators theory. For illustration, we propose a reaction–diffusion equation with state-dependent delay. The results obtained in this paper are a generalization of some existing results in this area.

• #nonlinear differential equations analysis
• #stability and controllability of differential equations
• #advanced mathematical modeling in engineering
• #state (computer science)

Mild solutions for some nonautonomous evolution equations with state-dependent delay governed by equicontinuous evolution families

Moussa El-Khalil Kpoumiè, Yannick-Levis Djeunankam, Joseph Mbang, Pierre Noundjeu

Malaya Journal of Matematik

In this work, we study the existence solutions and the dependence continuous with the initial data for some nondensely nonautonomous partial functional differential equations with state-dependent delay in Banach spaces. We assume that the linear part is not necessarily densely defined, satisfies the well-known hyperbolic conditions and generate a noncompact evolution family. Our existence results are based on Sadovskii fixed point Theorem. An application is provided to a reaction-diffusion equation with state-dependent delay.

• #nonlinear differential equations analysis
• #stability and controllability of differential equations
• #advanced mathematical modeling in engineering
• #equicontinuity

Stability and Hopf bifurcation of a CTL-inclusive HIV-1 infection model with both viral and cellular infections, and three delays

Martin Luther Mann Manyombe, Joseph Mbang, Gilbert Chendjou

Chaos Solitons & Fractals

• #mathematical and theoretical epidemiology and ecology models
• #evolution and genetic dynamics
• #evolutionary game theory and cooperation
• #hopf bifurcation

Global dynamics of a model of hepatitis B virus infection in a sub-Saharan African rural area

Jean Pierre II Kouenkam, Joseph Mbang, Yves Emvudu

International Journal of Biomathematics

We formulate and systematically study a deterministic compartmental model of Hepatitis B. This model has some important and novel features compared with the well-known basic model in the literature. Specifically, it takes into account the differential susceptibility that follows the vaccine formulation employing three-doses schedule. It points up the HbeAg status of carriers, their levels of viral replication, the fact that treatment being not curative is recommended only to a small proportion of chronic carriers, and finally the fact that only inactive carriers are able to recover from disease. The model has simple dynamical behavior which has a globally asymptotically stable disease-free equilibrium when the basic reproduction number [Formula: see text] and an endemic equilibrium when [Formula: see text]. By the use of Lyapunov functions, when it exists, we prove the global asymptotic stability of the endemic equilibrium under some conditions. Using data from Tokombere, a rural area in Cameroon, numerical simulations are performed. These numerical simulations first confirm analytical results, second they suggest that a policy based on treatment could not significantly impact the course of the infection. Third, they show as it is well known that vaccination is a very effective measure to control the infection. Furthermore, they show that neonatal vaccination influences more the course of infection than mass vaccination strategy. Nevertheless, they picture how much loss between consecutive doses of vaccine could be harmful. Finally, it is suggested that for a Sub-saharan African rural area, two-thirds of expected incidence of Hepatitis B virus infection and one third of expected prevalence of chronic carriers could be averted by 2030 if the birth dose vaccination becomes systematic and if mass vaccination rate increases to up 10%.

• #hepatitis b virus studies
• #hepatitis c virus research
• #hepatitis viruses studies and epidemiology
• #basic reproduction number

Mathematical Study of a Class of Epidemiological Models with Multiple Infectious Stages

Samuel Bowong, A. Temgoua, Y. Malong, Joseph Mbang

International Journal of Nonlinear Sciences and Numerical Simulation

Abstract This paper deals with the mathematical analysis of a general class of epidemiological models with multiple infectious stages for the transmission dynamics of a communicable disease. We provide a theoretical study of the model. We derive the basic reproduction number <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mi>R</m:mi> </m:mrow> <m:mn>0</m:mn> </m:msub> </m:math> $\mathcal R_0$ that determines the extinction and the persistence of the infection. We show that the disease-free equilibrium is globally asymptotically stable whenever <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mi>R</m:mi> </m:mrow> <m:mn>0</m:mn> </m:msub> <m:mo>≤</m:mo> <m:mn>1</m:mn> </m:math> $\mathcal R_0 \leq 1$ , while when <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mi>R</m:mi> </m:mrow> <m:mn>0</m:mn> </m:msub> <m:mo>&gt;</m:mo> <m:mn>1</m:mn> </m:math> $\mathcal R_0 \gt 1$ , the disease-free equilibrium is unstable and there exists a unique endemic equilibrium point which is globally asymptotically stable. A case study for tuberculosis (TB) is considered to numerically support the analytical results.

• #mathematical and theoretical epidemiology and ecology models
• #covid-19 epidemiological studies
• #evolution and genetic dynamics
• #combinatorics

Global properties of a tuberculosis model with lost sight and multi-compartment of latents

A. Temgoua, Malong Yannick, Joseph Mbang, Samuel Bowong

Journal of mathematical modeling

A  tuberculosis (TB) model with  lost sight  and multiple latent classes  is considered and studied. We derive the basic reproduction ratio $mathcal R_0$. There is always a globally asymptotically stable equilibrium state. Depending on the value of   $mathcal{R}_0$, this state can be either endemic ($mathcal{R}_0> 1$), or infection-free ($mathcal{R}_0leq 1$). The global asymptotic stability of equilibria is established using Lyapunov functions that combine quadratic, Volterra-type and linear functions. The theory is supported by numerical simulations.

• #mathematical and theoretical epidemiology and ecology models
• #evolution and genetic dynamics
• #fractional differential equations solutions
• #mathematics

Marketing Ricinodendron heudelotii Kernels and Gnetum spp. Leaves around Lobeke National Park, East Cameroon

Roseline Gusua Caspa, I.R. Tchouamo, Jean Pierre Mate Mweru, Joseph Mbang

Entrepôt pour orphelin

This study investigated the marketing of Ricinodendron heudelotii kernels and leaves of Gnetum buchholzianum/G. africanum around Lobeke National Park in Eastern Cameroon. Non-timber forest products (NTFP) supply chain actors were identified and their financial benefits and problems encountered in their activities assessed. Semi-structured interviews were conducted among 152 producers in eight villages and 120 traders in four markets. Direct actors are producers, wholesalers, retailers and consumers. The annual mean profits (AMP) of producers of R. heudelotii varied significantly between 120,013 FCFA in Kika and 23,992 FCFA in Koumela, whereas those of traders varied significantly between 442,880 FCFA in Yokadouma and 14,800 FCFA in Kika ( P=0.05). Producers of Gnetum spp. earned AMP between 324,740 FCFA in Mambele, and 74,657 FCFA in Koumela, while traders earned between 2,182,700 FCFA in Yokadouma and 1,397,933 FCFA in Moloundou (P=0.05). The problems encountered include difficulty to process and seasonality of R. heudelotii, long walking distances to collection sites and animal threats, low prices and lack of market information. NTFPs are collected from natural stocks and minimally processed using rudimentary tools. Domestication of NTFP species, improved processing and access to market and market information, collective action and establishment of local NTFP enterprises will enhance the benefits of actors.

• #african botany and ecology studies
• #agriculture and rural development research
• #forestry
• #geography

A metapopulation model for the population dynamics of anopheles mosquito

Martin Luther Mann Manyombe, Berge Tsanou, Joseph Mbang, Samuel Bowong

Applied Mathematics and Computation

• #mathematical and theoretical epidemiology and ecology models
• #evolutionary game theory and cooperation
• #evolution and genetic dynamics
• #metapopulation

Assessing the impact of the environmental contamination on the transmission of Ebola virus disease (EVD)

Berge Tsanou, Samuel Bowong, Jean Lubuma, Joseph Mbang

Journal of Applied Mathematics and Computing

• #viral infections and outbreaks research
• #covid-19 epidemiological studies
• #sars-cov-2 and covid-19 research
• #ebola virus

Global dynamics of a vaccination model for infectious diseases with asymptomatic carriers

Martin Luther Mann Manyombe, Joseph Mbang, Jean Lubuma, Berge Tsanou

Mathematical Biosciences & Engineering

In this paper, an epidemic model is investigated for infectious diseases that can be transmitted through both the infectious individuals and the asymptomatic carriers (i.e., infected individuals who are contagious but do not show any disease symptoms). We propose a dose-structured vaccination model with multiple transmission pathways. Based on the range of the explicitly computed basic reproduction number, we prove the global stability of the disease-free when this threshold number is less or equal to the unity. Moreover, whenever it is greater than one, the existence of the unique endemic equilibrium is shown and its global stability is established for the case where the changes of displaying the disease symptoms are independent of the vulnerable classes. Further, the model is shown to exhibit a transcritical bifurcation with the unit basic reproduction number being the bifurcation parameter. The impacts of the asymptomatic carriers and the effectiveness of vaccination on the disease transmission are discussed through through the local and the global sensitivity analyses of the basic reproduction number. Finally, a case study of hepatitis B virus disease (HBV) is considered, with the numerical simulations presented to support the analytical results. They further suggest that, in high HBV prevalence countries, the combination of effective vaccination (i.e. ≥ 3 doses of HepB vaccine), the diagnosis of asymptomatic carriers and the treatment of symptomatic carriers may have a much greater positive impact on the disease control.

• #mathematical and theoretical epidemiology and ecology models
• #covid-19 epidemiological studies
• #evolution and genetic dynamics
• #asymptomatic

Pesticides use in cocoa sector in Cameroon: characterization of supply source, nature of actives ingredients, fashion and reasons for their utilization

RJ Mahob, M. Ndoumbè-Nkeng, Gerben Martijn Ten Hoopen, Luc Dibog, Salomon Nyassé, M. Rutherford et 5 autre(s)

International Journal of Biological and Chemical Sciences

The chemical control is the widely control method applied in Cameroon for pests and diseases by all the cocoa producers without technical suitable assistance by the State as before 1980’S. However, it is known that farmers have less knowledge on the good pesticides use for the control of a specific pest. The objective of this study was to provide insight in current pesticide use in the cocoa sector in Cameroon. A stratified sampling scheme was used. A total of 251 cocoa farmers, 20 post-harvest cocoa traders and 37 chemical retailers were randomly selected and interviewed. The study showed that 35 different chemicals were marketed in Cameroon for use in cocoa: 4 herbicides, 11 fungicides and 20 insecticides. Of 251 farmers consulted, 96.8% said that they use pesticides on their farms while 3.2% did not. Fungicides were used most often by farmers 61.8%) followed by insecticides (38.2%). Eight active ingredients although, officially banned, were still being used on cocoa farms. Over 77% of farmers do not respect the official spray recommendations for chemicals. Moreover, 64% do not respect recommended doses. Two main pesticide-supply-pathways exist in Cameroon: a legal and illegal supply chain, which provides 51% of pesticides to cocoa farmers, resulting in an estimated loss of value added tax for the Cameroonian government of about 550 000 to 2.4 million Euros per year. These results suggest that improved pests and diseases control by the State and raising farmer awareness about pesticide use in cocoa could greatly attribute to more sustainable cocoa economy in Cameroon.Keywords : Cocoa, pesticides, insecticides, fungicides, Cameroon.

• #agriculture and rural development research
• #cocoa and sweet potato agronomy
• #african botany and ecology studies
• #pesticide

Adoption of new Technologies of Traditional Transformation of Products Made from Cocoa (Theobroma cacao L.) in Cameroon

Joseph Mbang, P Mounjouenpou, E Nossi, D Achukwi, S Bassanaga, Noé Woïn

International Journal of Engineering Trends and Technology

• #food chemistry and fat analysis
• #theobroma
• #sterculiaceae
• #transformation (genetics)

Cocoa Value Chain and Capacity Building of Women Cocoa-farmers for Sustainable Improve of Their Livelihoods: The Case of Mbangassina and Mbalmayo, Cameroon

P. Mounjouenpou, Joseph Mbang, Eric Joël Nossi, P. Mgome, Simon Bassanaga, S. A. Maboune Tetmoun et 2 autre(s)

Advances in life sciences

Women in the subdivisions of Mbalmayo and Mbangassina, Cameroon are important in the cocoa value chain. At the same time, Women and children are the most suffering of poverty, malnutrition, food insecurity in rural area. Normally, women should be able to benefit from these activities, but are unable to do so, due to inadequacies in capacity building to transform cocoa in a way that can sustain both resources and people. Strengthening capacities of women cocoa-farmers is underscored to be central in ensuring sustainable solutions to the problem of malnutrition, food insecurity and declining income of cocoa farmers, as well as empower female leadership skills. This study consists to build capacities of women cocoa farmers of Mbalmayo and Mbangassina regions for sustainable improvement of their livelihoods. Through field trips, meeting with village groupings and inquiries from individuals and groups, 185 women were interviewed and trained on the manufacture of cocoa butter, cocoa powder and soy-chocolate drink. Cocoa butter was among others, the most adopted innovative product, followed by cocoa powder and soy-chocolate drink. Due to that training, women have become more efficient in their household management. She have started generate more income due to the commercialization of the surplus of process product, and also contribute to the household charges. This study highlighted some of challenges affecting livelihoods of women cocoa farmers which are mainly the availability of cocoa beans because cocoa farm belongs to men, and the problem of inadequate material for local transformation.

• #agriculture and rural development research
• #cocoa and sweet potato agronomy
• #livelihood
• #business

Evaluation naturelle de l’impact de Beauveria bassiana : Champignon enthomopathogène dans la dynamique de population de Hypothenemus hampei , scolyte de baies des cerises de Coffea canefora

Joseph Mbang, Pauline Mounjouenpou, M. Mbarga Amougou, J. Mouen Bedimo, Salomon Nyassé, Luc Dibog et 1 autre(s)

African Crop Science Journal

A study of finding out natural enemies of the coffee cherry borer beetle Coffea canephora, Hypothenemus hampei (Ferrari) (Coleoptera, Scolytidae) was carried out at two ecologically different sites of Cameroon: Nkoemvone in the South region of the country and Nkolbisson around Yaounde in the central region. For six months, 500 berries were randomly collected monthly at each site. The presence of entomopathogenic fungus was observed on berries infested by the borer beetle. Rates of borer insect mortality due to Bauveria bassiana at Nkoemvone are: 70.6% in August, 64.6% in September, 32% in October, 43.2% in November, 39.2% in December and very low in January (8.6%). On the other hand, these rates at Nkolbisson are: 42.6% in October, 10% in November, 3.4% in December, 2.6% in January, 1.4% in February and 0% in March. From these observations, it was possible to carry out a research on the pathogenicity tests through its natural presence and on artificial-infection trials of the borer beetle with this fungus in order to protect better the coffee grains with a biological product.

• #entomopathogenic microorganisms in pest control
• #insect pest control strategies
• #insect resistance and genetics
• #coffea canephora

Influence du type de traitement post-récolte du cacao sur la teneur en ochratoxine-A (OTA) des fèves et des produits dérivés : exposition des consommateurs de l'OTA

Pauline Mounjouenpou, Noël Durand, Dominique Gueule, Joseph Mbang, Angélique Fontana, Bernard Guyot et 1 autre(s)

Agritrop (Cirad)

L'incidence des procédés post-récoltes sur la contamination du cacao par l'OTA a été étudiée au cours de 3 campagnes cacaoyères successives à Kumba au Cameroun. Le type de fermentation (caisse ou tas) n'a pas influencé de façon significative la teneur en OTA des fèves : la teneur maximale dosée est restée inférieure à 2ng.g [exposant] -1 qui est le seuil tolérable pour les fèves de cacao défini par l'Union Européenne. Par contre, les cabosses abîmées et l'écabossage tardif ont constitué des facteurs aggravants de la contamination du cacao par l'OTA. Une teneur de 75,5 ng.g [exposant] -1 a été obtenue avant la mise en fermentation et 32.2 ng.g [exposant] -1 après 4 mois de stockage y est obtenue : ce qui est très supérieure aux doses tolérables pour l'exportation. Suite aux statistiques nationales qui indiquent un niveau d'insécurité alimentaire et de malnutrition important en milieu rural, l'Etat camerounais incite à l'autoconsommation des denrées alimentaires. C'est dans ce cadre que certains cacaoculteurs ont commencés à transformer avec des techniques traditionnelles, une partie du cacao produit sous - forme de chocolat en pâte, poudre de cacao et beurre de cacao. A partir des fèves contaminées, ni le grillage au feu de bois, ni le décorticage par pilage au mortier n'ont fait baisser de façon significative la teneur en OTA des fèves. A l'exception du beurre de cacao, les autres produits de transformation de ces fèves ont des teneurs en OTA importantes. Soixante sept pour cent (67%) d'échantillon de chocolat en pâte et de poudre de cacao sont contaminés par I'OTA, avec 50% d'échantillon qui ont des teneurs supérieures à la norme. A cause de la fragilité de la pellicule des fèves dû aux cabosses blessées et à l'écabossage retardé de 10 jours, la contamination par l'OTA n'est plus superficielle et le décorticage ne contribue plus à faire baisser de façon significative la teneur en OTA des fèves. Au Cameroun, la consommation journalière moyenne des dérivés de cacao est estimée à 0.75 g.j [exposant] -1 chez l'adulte et à 1 g.j [exposant] -1 chez les enfants. L'exposition maximale journalière à l'OTA pourrait être de l'ordre de 1.6l ng.kg [exposant] -1 p.c/j chez les jeunes enfants d·environ 20kg. Le cacao est donc une source d'exposition minimale à l'OTA, mais ne tardera pas à devenir un risque si rien n'est fait.

• #cocoa and sweet potato agronomy
• #food chemistry and fat analysis
• #agriculture and rural development research
• #humanities

Biodiversity of Potentially Ochratoxin : A Producing Black Aspergilli Related to the Cocoa Bean Post-Harvest Processing

P Mounjouenpou, Joseph Mbang, Mama Ntoupka, Bernard Guyot, A. Tachon-Fontana, J. P. Guiraud et 1 autre(s)

Journal of natural product and plant resources

The aim of this work was to study the incidence of the post-harvest processing on the morphological and molecular diversity of the potentially ochratoxigenic Aspergillus species of the Nigri section isolated from cocoa beans. For three successive cocoa growing seasons in Cameroon, black Aspergillus species isolated during different post-harvest processes were studied by phenotypic and molecular techniques. Their identification by PCR techniques with specific primers allowed to separate A. carbonarius from A. niger aggregate. A study of the genomic profiles obtained by RAPD-PCR for A. niger aggregate and A. carbonarius showed an important biodiversity that depended on neither the year of the cocoa growing season nor the post-harvest treatment or the bean processing stage.

• #cocoa and sweet potato agronomy
• #ochratoxin a
• #aspergillus niger
• #biology

MODELING AND ANALYSIS OF HIV AND HEPATITIS C CO-INFECTIONS

Dany Pascal Moualeu-Ngangue, Joseph Mbang, René Ndoundam, Samuel Bowong

Journal of Biological Systems

Infection with the hepatitis C virus (HCV) is the most common coinfection in people with the human immunodeficiency virus (HIV), and hepatitis C is categorized as an HIV-related illness. The study of the joint dynamics of HIV and HCV present formidable mathematical challenges in spite the fact that they share similar routes of transmission. A deterministic model for the co-interaction of HCV and HIV in a community is presented and rigorously analyzed. The disease-free equilibrium is shown to be locally asymptotically stable when the associated epidemic threshold known as the basic reproduction number for the model is less than the unity. The Centre Manifold theory is used to show that the HCV only and HIV/AIDS only endemic equilibria are locally asymptotically stable when their associated reproduction numbers are greater than the unity. We compute two coexistence thresholds for the stability of boundary equilibria. Numerical results are presented to validate analytical results.

• #mathematical and theoretical epidemiology and ecology models
• #hepatitis c virus research
• #covid-19 epidemiological studies
• #coinfection

Analyse de la stabilité des modèles intra-hôtes avec retard : application à des modèles intra-hôtes de paludisme et de V.I.H-1

Joseph Mbang

Dans cette thèse, nous analysons certains modèles épidémiologiques comportant des retards distribués. Le phénomène du retard est omniprésent en biologie. Les équations différentielles avec retard constant discret encore appelées "lag", ont été beaucoup étudiées. Cependant les retards distribués sont plus adaptés aux phénomènes biologiques. Nous entendons par retards distribués, des retards qui sont décrits par une fonction continue de densité de probabilité. Les retards jouent un rôle important en biologie plus particulièrement en épidémiologie. Par exemple dans le cas d'une maladie infectieuse, le temps d'incubation c'est-à-dire le temps entre le moment où l'individu est infecté et celui où il transmet cette maladie joue un rôle important dans l'analyse de la transmission. Un autre exemple est celui des modèles intra-hôtes d'une infection. Un parasite a besoin d'envahir une cellule cible pour se reproduire. C'est le cas de Plasmodium falciparum, le parasite du paludisme qui envahit les globules rouges, ou le virus VIH dont les cellules cibles sont les lymphocytes CD+4. Quand le parasite rentre dans la cellule cible cela déclenche toute une cascade d'évènements qui aboutiront à la production de nouveaux parasites par bourgeonnement ou lyse de la cellule. (HIV, HBV, Paludisme). La production de nouveaux parasites n'est pas instantanée. Plus généralement le mouvement de quantité de matières d'un endroit à un autre prend du temps. Si l'on veut modéliser une injection de substance dans le flot sanguin, le temps d'apparition dans les capillaires introduit un retard. Les modèles étudiés dans cette thèse sont des modèles intra-hôtes avec retard. Les modèles intra-hôtes ont pour objectif de décrire la dynamique des différents niveaux d'étapes de parasites ainsi que leur interaction avec les cellules cibles du parasite. Pour les modèles biologiques les systèmes compartimentaux sont naturellement utilisés dans la modélisation. Le retard est modélisé par la fonction d'Erlang comme fonction de densité de probabilité. Les modèles intra-hôtes de parasite avec retard peuvent aussi être vus comme les systèmes provenant des modèles SE1...En I, où les Ei sont les classes latentes des infectés. Les classes latentes sont représentées par des chaînes linéaires parallèles de différentes longueurs qui sont insérées entre le compartiment des susceptibles et celui des infectieux. Dans cette thèse, nous utilisons quelques outils de la théorie du contrôle pour "généraliser" le "linear chain trick". Nous calculons le nombre de reproduction de base R0 pour ces systèmes considérés et nous établissons les résultats suivants : – si R0 &lt; 1 les parasites disparaissent et l'équilibre sans parasite (PFE) est globalement asymptotiquement stable dans l'orthant positif ; – si R0 &gt; 1 et avec une hypothèse supplémentaire, il existe un équilibre endémique (EE) qui est globalement asymptotiquement stable dans l’orthant positif hormis l’axe des « susceptibles ». Ces résultats donnent une possibilité de relecture de certains modèles de parasites incluant le retard intracellulaire et d'étude de leur stabilité globale. Comme application de ce résultat, nous reprenons et améliorons les résultats de Nelson et Perelson dans sur les modèles intra-hôtes de l'infection au VIH

• #mathematical and theoretical epidemiology and ecology models
• #covid-19 epidemiological studies
• #mathematical biology tumor growth
• #protozoal disease

Effect of genotype of cocoa ( Theobroma cacao ) on attractiveness to the mirid Sahlbergella singularis (Hemiptera: Miridae) in the laboratory

Luc Dibog, Régis Babin, Joseph Mbang, Bernard Decazy, Salomon Nyassé, Christian Cilas et 1 autre(s)

Pest Management Science

BACKGROUND: Mirids are a major constraint to cocoa growing in Africa. Cocoa breeding for tolerance/resistance could be effective in an integrated pest management system. Attractiveness is one aspect of tolerance/resistance, and decreasing the attractiveness of cocoa trees should be a good way of reducing damage. RESULTS: Small-scale laboratory tests were carried out in Cameroon to assess differences in the attractiveness to mirids of eleven cocoa genotypes. The genotypes were ranked according to their attractiveness score and a distance from a mean value. An analysis of variance was performed and revealed significant differences between cocoa genotypes (F=3.15, P<0.001). The cocoa genotype groupings revealed three major categories, with BE10 and SNK413 proving to be the most attractive. In contrast, five genotypes, IMC60, the Catongo Trinitario genotypes, Playa Alta2 (from Venezuela), SIC5 and SNK614, proved to be less attractive than the mean. Four genotypes (PA107, SNK619, UPA134 and T60/887) displayed similar attractiveness to the mean. CONCLUSION: The circular microtest offered the advantage of not needing a reference cocoa genotype. The least attractive clones, such as IMC60, were also the most tolerant in the field. Comparisons with the results of other studies are proposed.

• #cocoa and sweet potato agronomy
• #miridae
• #theobroma
• #biology

Evaluation of Ensiled Brewer's Grain in the Diet of Piglets by One Way Multiple Analysis of Variance, MANOVA

Joseph Mbang, Jackton A Owino, Julius K. Kones, François Meffeja, Luc Dibog

Tropicultura

1 Institute of Agricultural Research for Development (I.R.A.D.), Cameroon. 2 Correspondent author: I.R.A.D., P.O.Box 2067, Yaounde, Cameroun. Mail: mbang4@yahoo.com 3 University of Nairobi, Department of Mathematics, P.O.Box 30197, Nairobi, Kenya. 4 Institute of Agricultural Research for Development, Cameroon, P.O.Box 2067, Yaounde, Cameroun. Received on 22.04.04 and accepted for publication on 21.12.05. Summary

• #genetic and phenotypic traits in livestock
• #statistical methods and applications
• #genetics and plant breeding
• #multivariate analysis of variance

Multi-compartment models

Abderrahman Iggidr, Joseph Mbang, Gauthier Sallet, Jean Jules Tewa

HAL (Le Centre pour la Communication Scientifique Directe)

International audience

• #mathematical and theoretical epidemiology and ecology models
• #evolution and genetic dynamics
• #stochastic processes and statistical mechanics
• #orthant

Activities carried out to evaluate cocoa resistance to mirids ( Sahlbergella singularis ) at IRAD, Cameroon

Régis Babin, Jean-Michel Mpe, Luc Dibog, Joseph Mbang, Salomon Nyassé, Albertus Eskes

Agritrop (Cirad)

Field and laboratory tests were conducted for different components of the resistance of cocoa to mirids (Sahlbergella singularis) at the Nkoemvone and Nkolbisson research stations of IRAD as part of the CFC/ICCO/IPGRI project activities in Cameroon. Almost 40 local or international genotypes were tested for one or for several components of resistance. Laboratory micro-tests were used to assess attractiveness. Antixenosis was measured by enclosing mirid nymphs in sleeve cages on young flushes. Attractiveness and antixenosis were estimated in the same set-up by counting the feeding points after 24 hours. Ability to recover from mirid damage (tolerance) was assessed by observing degradation of twigs with time. Finally, antibiosis tests were conducted with the aphid Toxoptera aurantii, with the aim of evaluating whether this aphid could be used as an indicator for cocoa antibiosis towards mirids. Statistical analysis generally revealed a strong effect of genotypes on the different components of the resistance. However, there was no significant difference between the genetic groups studied (Upper Amazon and Lower Amazon Forasteros, Trinitarios and hybrids), which appears to be in contrast with field observations on mirid damage in Côte d'Ivoire. We also failed to identify genotypes that combine favourable responses to several resistance components. As an important result, the activities have made it possible to improve and standardize the evaluation methods. Mechanisms involved in attractiveness and antixenosis appeared to be similar, therefore one test should be enough to evaluate these components. We propose to standardize the methods for antixenosis (under no-choice conditions) and tolerance. We suggest that a new assessment method be developed for the effect of genotype on antibiosis (female mirid fecundity and nymph survival), using cocoa pods on the tree as the feeding and egg-laying environment. Finally, we propose to include in our future activities studies on resistance of cocoa to fungal pathogens that may be associated with mirid damage, with the aim of achieving a better understanding of tolerance and dieback.

• #cocoa and sweet potato agronomy
• #agriculture and rural development research
• #antibiosis
• #aphid

Effect of genotype on cocoa (Theobroma cacao L.) attractiveness towards mirids

Luc Dibog, Régis Babin, Joseph Mbang, Bernard Decazy

Agritrop (Cirad)

Laboratory tests were performed in Cameroon in order to assess the level of attractiveness of eleven cocoa genotypes towards mirids. Clones were ranked according to their attractiveness score and from a distance to a mean value. An analysis of variance was performed and showed significant differences between cocoa clones (F=3.15, p&lt;0.0006). The cocoa clones grouping reveals three major categories, with BE10 and SNK413 showing the highest attractiveness. In contrast, five clones, IMC60, the Catongo trinitario clones, Playa Alta2 (from Venezuela), SIC5 and SNK614 showed a lower attractiveness than the mean. Four Clones (PA107, SNK619, UPA134 and T60/887) showed attractiveness similar to the mean. The circular micro-test has the advantage that it does not need a reference cocoa clone. Comparisons with results of other studies are proposed. (Texte intégral)

• #cocoa and sweet potato agronomy
• #attractiveness
• #theobroma
• #biology

Evaluation of influence of fungus Beauveria bassiana in the dynamic population of Hypothenemus hampei (Ferrari), pest of coffee berry borer in Cameroon

Joseph Mbang, Luc Dibog, Régis Babin, Alain Didier Missoup, Michael Mbenoum

Le scolyte des cerises de cafeier, Hypothenemus hampei (Ferrari) (Coleoptera, Scolytidae), est l'un des plus serieux ravageurs du cafe robusta commercialise; une etude de lutte biologique a ete menee dans deux sites au Cameroun: Nkoemvone dans la province du Sud du pays et Nkolbisson pres de Yaounde, dans la province du centre. Pendant six mois, 500 baies etaient mensuellement prelevees au hassard dans chaque site. Les observations sur le champignon entomopathogenes etaient realisees au laboratoire sur les baies attaquees par les scolytes. Le nombre de Baies portant le champignon entomopathogene Bauveria bassiana (Bals.). s'est revele plus significativement eleve a Nkolbisson qu'a Nkoemvone. Les observations sur les scolytes morts ont ete aussi significativement plus eleves a Nkolbisson, par contre celles sur les scolytes vivants etaient significativement tres faible dans ce meme site. Dans les 2 sites, le taux de mortalite du scolyte due a Bauveria bassiana etait plus eleve en periode humide (Septembre et Octobre) qu'en periode seche (Decembre a Fevrier). Ces deux sites ont besoin d'un apport par infection artificielle du B. bassiana pour une strategie de lutte biologique conte for H. hampei. (Texte integral)

• #insect pest control strategies
• #entomopathogenic microorganisms in pest control
• #insect resistance and genetics
• #beauveria bassiana

Cocoa productivity and quality improvement, a participatory approach : results from studies on cocoa attractiveness, antixenosis, antibiosis and tolerance towards mirids in Cameroon

Régis Babin, Luc Dibog, Hervé Bisseleua, Jean-Michel Mpe, Joseph Mbang, Constantin Onana

Agritrop (Cirad)

• #cocoa and sweet potato agronomy
• #agriculture and rural development research
• #antibiosis
• #productivity