Patterns of the tapeworm Raillietina trapezoides infection in the fat sand rat Psammomys obesus in Tunisia: season, climatic conditions, host age and crowding effects

Abstract

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.

A survey study on the helminth parasites of two wild jirds,Meriones shawiandM. libycus(Rodentia: Gerbillinae), in Tunisian desert areas

“…Raillietina species have been reported as parasites of Meriones spp. as well as of other gerbillin and Dipodidae rodents: Gerbillus spp., Psammomys obesus (Fichet-Calvet et al 2003) and Jaculus jaculus (Wertheim et al 1986;Ben Faleh et al 2012); here we report two Meriones species as definitive hosts for this helminth.…”

“…Some studies (e.g. Fichet-Calvet 2003;Ben Faleh et al 2012) consider that the Raillietina species parasites of rodents is R. trapezoïdes for which the number of egg cells in each capsule is known to be around 25; however, Raillietina specimens found in the current study showed different numbers of cells. This result requires further taxonomic study of these specimens to determine their parasitic entities.…”

Ultimate mechanisms of age-biased flea parasitism

“…There are various examples of either increases (see Fichet-Calvet et al 2003 and references therein), decreases (Henricson 1977;Quinnell 1992;Davies and Gavgani 1999;Knudsen et al 2002) or Wrst an increase and then a decrease (convex age-infestation curve; Gregory et al 1992;Sorci 1996) in infestation level with host age. The shape of the relationship between host age and parasite infestation seems to depend on both host and parasite taxa (Wilson et al 2002;Hawlena et al 2005 and references therein), but it is usually consistent within a parasite-host association.…”

The Relationship between Parasitic Fleas and Small Mammals in Household of Western Yunnan Province, China

“…environmental stress) [37] and may also differ between males and females (due to faster aging of men) [38]. Secondly, differential parasite abundance in hosts belonging to different age cohorts has been reported for various host and parasite taxa [39–41]. However, the influence of host age on the distribution pattern of parasite abundance differs among different host-parasite associations.…”

“…However, the influence of host age on the distribution pattern of parasite abundance differs among different host-parasite associations. In some host-parasite associations, the abundance of parasites increases with the age of the host [39], while in other associations it increases or decreases in the youngest and oldest hosts compared to hosts of median age (called “adult hosts”)[40]. In fact, acquired resistance against parasites may be lower in young or old hosts than in median-age hosts.…”