R Djidjou Demasse

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R Djidjou Demasse

Ramsès Djidjou Demasse

Post-doctorant

ramses.djidjou@inra.fr
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Thème de recherche : Modélisation de la durabilité des résistances au mildiou et à l'oïdium des cépages de vigne

  • encadrants : Frédéric Fabre et François Delmotte (UMR SAVE), Arnaud Ducrot et Jean-Baptiste Burie (Institut Mathématiques de Bordeaux, IMB)
  • avril 2015 - aout 2017
  • financeurs: Conseil Interprofessionnel du Vin de Bordeaux (CIVB), Agreenskills

Objectif :

Achieving durable plant resistance is a key to sustainable management of pathogens and pests in agriculture. In particular, the allocations in time and space of the susceptible (S) and resistant (R) crops in agricultural landscapes is a key factor that needs to be optimized. In turn, this implies to model both the spread of the pathogen in a heterogeneous landscape composed of S and R hosts and the dynamics of its adaptation to these hosts. 

The project (multidisciplinary project) is aiming to model the evolutionary epidemiology of a plant disease of vineyard in order to manage the durability of host resistance (and thus to decrease pesticide use). Simulations of this model, possibly coupled with an optimal control or viability approach, should yield practical insights on the optimal deployment in time and space of resistant hosts in the vineyards. 

Publications :

  • Djidjou-Demasse R, Ducrot A, Fabre F (2017) Steady state concentration for a phenotypic structured problem modeling the evolutionary epidemiology of spore producing pathogens. Math. Models Methods Appl. Sci. 27 (2) 385, DOI:10.1142/S0218202517500051
  • Delmotte F, Mestre P, Schneider C, Kassemeyer HH, Kozma P, Richart-Cervera S, Rouxel M, Delière L (2014) Rapid and multiregional adaptation to host partial resistance in a plant pathogenic oomycete: Evidence from European populations of Plasmopara viticola , the causal agent of grapevine downy mildew. Inf. Genet. Evol., 27, 500–508.
postdoc resitance-mildiou

Voir aussi

Téléchargez le CV de R. Djidjou Demasse

Thèse

Structured Models and Bifurcations in Delay Differential Equations

This work deals with a recent within-host malaria infection model with multi-strain for the parasites and a spatial modeling of anopheles mosquito dynamics population. In this work, we also consider models of infectious disease into the host population structured by age. Namely, Hepatitis B virus (HBV) model and Susceptible-Infected-Lost of sight (SIL) model for the spread of a directly transmitted infectious disease taking into account demographic process and vertical transmission of the disease.

The malaria model has been conceived, since it is well grounded that malaria is a multi-strain infection. However other parasitic infections can be considered by this model, e.g., the model can be extended to the HIV infections. Our study allowed for the observation of competitive suppression, the reduction of parasites numbers due to the presence of another parasite, and competitive release, the improved performance of a parasite after the removal of a competitor. These studies demonstrated that the presence of two parasites led to the reduction in density of at least one parasite.

According to HBV model, we find that mass vaccination of infants increases the average age of infection in unimmunized individuals and shifts the average age at infection to older age groups. This indicates that mass vaccination in infants might be not enough to control the infection and eradicate the virus. A control strategy consist in a combination of immunization of newborns, immunization of susceptible individuals (at least young adults), and reduction of perinatal infection.

Publications

  • R. Djidjou Demasse, J.J. Tewa, S. Bowong. A malaria model with seasonality, submitted to Journal of Mathematical Biology.
  • R. Djidjou Demasse, J.J. Tewa, S. Bowong, Y. Emvudu (2016) Optimal control of an age-structured model for the transmission of hepatitis B with differential infectivity, Journal of Mathematical Biology, 1-29 DOI 10.1007/s00285-015-0952-6
  • P. Tchinda, R. Djidjou Demasse, J.J. Tewa and M.A. Aziz-Alaoui (2015) Bifurcation analysis and optimal harvesting of a delayed predator-prey model, International J. of Bifurcation and Chaos, 25 (1) 
  • R.  Djidjou Demasse, J.J. Tewa and S. Bowong (2014) Analysis of an Age-structured SIL model with demographics process and vertical transmission, Arima Journal, 17, 23-52
  • R. Djidjou Demasse and A. Ducrot  (2013) An age-structured within-host model for multi-strain malaria infections. SIAM Journal on Applied Mathematics, 73 (1) 572-593  doi:10.​1137/​120890351
  • Y. Emvudu, R. Djidjou Demasse, D. Djeudeu (2013) Optimal control using state dependent Riccati equations in a tuberculosis model. Computational and Applied Mathematics, 32 (2) 191-210
  • J.J.Tewa, R. Djidjou Demasse, S. Bowong (2012) Predator-prey model with prey harvesting, Holling response function of type III and SIS disease. Biomath 1 (2) Article ID: 1210231
  • Y. Emvudu, R. Djidjou Demasse, D. Djeudeu, (2011) Optimal Control of the Lost to Follow Up in a Tuberculosis Model. Computational and Mathematical Methods in Medicine, 2011, 1-12 

Date de modification : 14 août 2023 | Date de création : 08 avril 2015 | Rédaction : SC