%0 Journal Article %T Patterns of the tapeworm Raillietina trapezoides infection in the fat sand rat Psammomys obesus in Tunisia: season, climatic conditions, host age and crowding effects %+ Liverpool School of Tropical Medicine (LSTM) %+ Laboratoire d'Epidémiologie et d'Ecologie parasitaire, Institut Pasteur de Tunis %A Fichet-Calvet, E. %A Wang, Juefei %A Jomaa, I. %A Ben Ismail, R. %A Ashford, R., W. %Z This study forms part of a project on the ecological interaction between P. obesus and cutaneous leishmaniasis, funded by the Avicenne Programme of the European Commission, AVI CT92/0018. E.F.C. benefitted from a grant from the Societe de Secours des Amis des Sciences (Paris) %< avec comité de lecture %@ 0031-1820 %J Parasitology %I Cambridge University Press (CUP) %V 126 %N 5 %P 481-492 %8 2003 %D 2003 %R 10.1017/S0031182003003056 %M 12793653 %K temporal dynamics %K prevalence %K population structure %K Raillietina trapezoides %K Psammomys obesus %K parasite burden %Z Life Sciences [q-bio]/Microbiology and Parasitology/ParasitologyJournal articles %X The tapeworm Raillietina trapezoides was studied in a Tunisian population of the fat sand rat Psammomys obesus. Seasonal changes in the abundance of parasite and host were monitored in a longitudinal field survey lasting 20 months. In total 582 intestinal samples were collected during 10 trapping sessions between May 1995 and January 1997 and examined. The impact of abiotic and biotic factors on the prevalence and parasite burden were explored, using generalized linear models. R. trapezoides showed a seasonal pattern with most transmission occurring in summer and autumn. In August-September when the rodents were at low density and most adult (90-100%) were infected. In winter, infections with R. trapezoides were highly prevalent in the cohort of adults only. The worm burden by number was also high in late summer and autumn. Prevalence and parasite burden by number or by biomass were highly age dependent. Season and age act in synergy so that the rodents were highly infected in late summer and autumn. Unusually dry conditions in winter seemed to increase prevalence and to reduce the number of worms. There was no difference between males and females in prevalence or parasite burden (by number or by biomass). Prevalence was not correlated with the relative density of the hosts whereas parasite burden depended upon their densities. The more numerous the worms were, the smaller they were individually, reflecting a crowding effect. The possibility of an immune response regulating P. obesus is discussed, in regard to the very high natural prevalence and the variation in worm burden, and compared with other parasite-host systems. %G English %Z We are grateful to Guila Ganem (Institute for Evolution Sciences at Montpellier II University) and Khiem Dang Van for helping in the statistical analysis and two anonymous reviewers for improving this paper in this earlier version %L pasteur-02049492 %U https://riip.hal.science/pasteur-02049492 %~ RIIP %~ RIIP_TUNIS