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International audience; The need for use of quantitative methods for characterizing variability and uncertainty in risk assessment has received increasing attention in recent years, while few software packages are able to deal with it. Moreover, models and sensitivity analysis methods are getting more and more sophisticated, and consequently the available software packages might not be flexible enough to deal with new methods. We developed, initially for our own use, “mc2d”, a specific R package to build and study two-dimensional Monte-Carlo simulations. R is an open-source integrated suite of software facilities for data manipulation, calculation and graphical display extended by a large collection of packages where up-to-date statistical methods are implemented. “mc2d” is an additional set of integrated functions specifically written to: i) build distributions: with additional specific distributions and tools to choose and fit distributions on available data, to estimate and model uncertainty on the parameters by bootstrap, to build correlation structure between parameters, etc.; ii) build models: the package transfers easily variability and uncertainty along a mathematical model; iii) study the model: through ad-hoc summaries and graphics, sensitivity analyses (rank correlation on the variability or the uncertainty dimension, ANOVA), etc. The R environment allows a flexible use of any methods implemented in the basic distribution or any additional package. Less “user friendly” than some of the commercially available programs, “mc2d” is suitable for users with intermediate experience with R. A training session performed in France demonstrated that students with no prior experience with R are able to develop their own models in few days. The presentation will provide an overview of “mc2d,” illustrated by an example in the food safety domain. “mc2d” is available on request to the authors.

50 ref.; International audience

International audience; To determine the prevalence of hepatitis C virus (HCV) infection and genotype distribution in a rural isolated area of Central Africa, plasma of 409 Bantous (mean age, 32 years; range, 2-78 years) living in a remote village of the rain forest of Southern Cameroon was screened for anti-HCV antibodies. HCV seropositive samples were also subjected to qualitative detection of viral RNA. HCV antibodies were detected in 70 (17.1%) individuals, 48 (68.8%) of whom had detectable viremia. The seroprevalence did not differ by gender (P = 0.37), but increased significantly with age (P < 0.05), with a strong increase in the oldest age groups. Indeed, nearly one-half (48%) of the adults >50 years old were HCV seropositive. The characterization of the viral genotypes indicated that most of the HCV strains were of genotype 4 (76%), while genotype 2 (16%), and 1 (8%) were marginally represented. The results suggest a cohort effect with an old, possibly iatrogenic, group exposure rather than a continuous exposure. A more in-depth population-based epidemiological study is needed to address this issue further.

*INRA Biométrie Jouy-en-Josas (FRA) Diffusion du document : INRA Biométrie Jouy-en-Josas (FRA); International audience

National audience

58 ref. 7 tables; National audience; The Nematode Haemonchus contortus, the Cestode Moniezia sp. and the protozoa Eimerics spp. are the main digestive parasites of small ruminants in the Caribbean. Models of infective third stage larvae (L3) of Haemonchus contortus and Trichostrongylus colubriformis have been established to use simulation to estimate the infestation risk according to season, irrigation practice, herbage mass and pasture management. The faunistic diversity is low: 10 species of worm in Guadeloupe. The prevalence of Haemonchus sp. and Trichostrongylus spp. range hom 80 to 100%. Incidences of these worms are higher than 60% per month. The main sources of variation in infestation risk are irrigation, climate and susceptibility of animals. The strongylosis is responsible for more than 80% of the mortality rate before weaning,which raises to 40% Resistance of Haemonchus contortus strains to anthelmintics (benzimidazoles) are common in Guadeloupe and Martinique. All the studies on farms confirmed that digestive strongylosis is the main disease of small ruminants in the Lesser Antilles. The research carried out by the Animal Production Research Unit of INRA to improve animal breeding and husbandry in pasture (type of forage, stocking rate recommendations, mixed grazing, etc...) took into account the importance of strongylosis to small ruminants production. The genetic resistance of creole goats to digestive strongles and the possible use of feeding supplements are being studied for integration in a plan to control these parasitic diseases.; Les parasitoses digestives, pathologie majeure des petits ruminants de la zone Caraïbe, sont dues essentiellement à une espèce de Nématode, Haemonchus contortus et, dans une moindre mesure, à une espèce de Cestode, Moniezia sp., et un ensemble de protozoaires du genre Eimeria . Des études en station expérimentale et en fermes ont permis de définir les dynamiques des larves infestantes d’Haemonchus contortus et de Trichostrongylus colubriformis sur le pâturage. Les risques d’infestation parasitaire ont été ensuite quantifiés par des modélisations et des simulations selon la saison, l’irrigation, la biomasse herbacée sur le pâturage et le mode de gestion du pâturage. En Guadeloupe, la diversité faunistique des populations vermineuses est faible : 10 espèces. Les prévalences d’Haemonchus sp. et Trichostrongylus spp. varient entre 80 et 100 %. Les incidences dépassent très fréquemment 60 % par mois pour ces genres. Les facteurs relatifs à l’eau (irrigation, régions sèches ou humides) ou à la réceptivité des hôtes (âge par exemple) sont les principales sources de variation du risque d’infestation parasitaire par les strongles digestifs. Plus des trois quarts de la mortalité avant le sevrage (soit 40 %) sont liés pour tout ou partie aux strongles gastro-intestinaux. L’utilisation fréquente des anthelminthiques a induit l’apparition de résistances d’Haemonchus contortus aux benzimidazoles dans toute la Guadeloupe et la Martinique. Les études en fermes ont confirmé que les strongyloses gastro-intestinales sont la pathologie dominante des petits ruminants des petites Antilles. Les recherches pour améliorer les techniques d’élevage au pâturage menées à l’Unité de Recherches Zootechniques de l’INRA (rotation, pâturage mixte avec les bovins) tiennent compte des répercussions des strongyloses sur les productions. Des études sont menées sur la résistance génétique aux strongles digestifs chez les caprins Créoles et l’intérêt de complémentations alimentaires dans des plans de lutte intégrée contre ces parasitoses.

International audience

International audience

International audience

International audience