PARENT SESSION
Poster Session 17: Modelling
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Modelling the population dynamics oh helminths, parasites of vertebrates : multiple scales, demographic strategies and mathematical implications.

Silan, Patrick¹, Latu, Guillaume^*,2, Langlais, Michel^*,3, Roman, Jean^*,4, ¹ CNRS GUYANE (UPS 2561), 97300 Cayenne, GUYANE FRANCAISE² LSIIT – UMR CNRS 7005, Strasbourg, FRANCE³ MAB - UMR CNRS 5466, Bordeaux, FRANCE⁴ LaBRI – UMR CNRS 5800, Bordeaux, FRANCE

ABSTRACT- Most biomathematical approaches to host-parasite systems are concerned with infectious processes. Corresponding epidemiological models are not well-adapted to macroparasites. These organisms pose specific problems of diffusion or propagation at all levels of organisation : individual, populations, species. Overdispersion processes are fundamental and determine for one part the regulation of both populations. A central issue is therefore a reliable description of these processes and their interactions with the dynamics of these systems, and that at different scales. These latters present complex demographic behaviors, and classical deterministic models (infinite series of ordinary differential equations) do not provide tools powerfull enough to give details of all specific situations ; they describe only macroscopic phenomena. Discrete mathematical models, deterministic and stochastic, describing the demographic strategies of a host-parasite system, have been developped. They integrate spatial (host population...) and temporal (cohorts of parasites...) heterogeneities, but require heavy computations. The implementation of these models on a sequential simulator is prohibitive ; parallelization is essential and an implementation of new computing shemes is necessary. A detailed algorithmic study has been necessary in order to update the temporal changes of parasite distribution in a host population. A individual-centered approach, reproducing the interactions of each parasite with each host instead of considering their distribution, has also been developped. Others detailed results are obtained, and provide complementary information compared with the other models. Several levels of parallelism have been tested, and we have now a very high performance parallel simulator based on these original models. The accuracy of the computation has been improved, allowing to observe new population dynamics at different levels of organisation. One goal of this research is to describe the hierarchy of various mecanisms involved in such coupled populations, giving ecological but also epidemiological answers. Using the sea bass-Monogenean model, the contribution of a interdisciplinary approach combining closely population biology, mathematics and science computing is emphasized.

Key words: Parasite, Vertebrate, Population dynamics, Ecological modelling