Host factors affecting abomasal parasites in Alpine Ibex

Alpine ibex is characterized by strong sexual differences, both morphological and in population dynamics. Host sex has been shown to strongly affect parasite load with males usually more infected than females. Moreover ibex exhibit a peculiar pattern of survival with subadult males having a slow growing rate coupled with high survival which rapidly decline in old individual.This peculiar life history has been suggested to have been developed as adaptation to an harsh environment. In this way by investing fewer resources in growing the ibex can direct more energy in survival. At the same time the investment in immunodefence can change over the age. To verify the hypothesis that sex and age affect parasite infection, we analysed the abomasal parasite community of swiss ibexes shot during the 2007 hunting season. We analysed the parasite community of 31 abomasa coming from 17 males,12 females, ranging from 1 to 16 years old. The ibex analysed harboured a mean of 1472 helminth/individual. Seven parasites species have been identified with Teladorsagia circumcincta and Marshallagia marshalli covering the 90% of total parasite count. The mean abundance of total parasite count and of M. marshalli was different between sexes, with more parasites found in males. Age alone did not show any significant effect, but its interaction with sex evidenced different relationship such as T. circumcincta increased with age in males and decreased in females. While these data suggest the influence of sex and age on parasitic infection a comparison with other sampling areas, year and season is needed.