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The influence of host and parasite-related factors on the strongyle infection in 50 horses coming from 6 European countries and slaughtered in Italy for meat production was investigated using a multivariable modelling approach. The study was carried out by examining adult helminths, faecal eggs (identified by culture to the third larval stage) and mucosal larval stages of Cyathostominae. A modified Transmural Illumination technique (TMI) has been performed and Cyathostominae empty mucosal cysts were also evaluated in order to obtain further indications about small strongyles dynamic. All species found in this study were previously reported in European horses. Major differences were detected comparing Hungarian (#24) and Italian (#13) horses. Sex was confirmed as uninfluential, while relations with host age were only partially consistent with the development of acquired resistance. The analysis of both mucosal Cyathostominae larvae (more in Italy) and of the percentage of empty cysts (higher in Hungary) along with lower large strongyle abundance in Hungary allowed to hypothesise a wider use of anthelmintic treatments in Hungarian horses compared to Italian ones. The results regarding adult Cyathostominae (no significant differences nor regarding age or origin) suggested the important role of ecological interactions between larval and adult stages in regulating small strongyle populations., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The spatial distribution of large intestinal helminth parasites of 50 horses was studied. Both adult and mucosal larval stages were examined and counted within the ventral colon, dorsal colon and caecum. Thirty-three species of adult parasites were identified and their distribution in the three large intestinal regions reported, together with the localization of cyathostome encysted larvae and of empty mucosal cysts. In order to highlight interspecific interactions, both Spearman pairwise correlation (among all parasites) and multivariable negative binomial regression (among the most abundant parasites) were performed. Interactions among parasite species are very important from the ecological and parasitological point of view as they can modulate the abundance and the spatial distribution of parasites, as well as the composition of the infracommunity. The main results were: the selection of preferred sites of horse's large intestinal helminths has been confirmed; all statistically significant pairwise correlation coefficients (359 out of 666) were positive; the build up of multivariable regression models brought to light both negative and positive interactions; the most interesting competitive interactions have been observed between the most abundant and relatively large strongyle species: Strongylus edentatus and Strongylus vulgaris in the caecum and ventral colon. When S. edentatus is in the caecum, the favourite site of S. vulgaris, the latter decreases especially in the caecum. On the other hand, when S. edentatus is in the ventral colon, its favourite site, there is no negative relationship with S. vulgaris in the ventral colon and the positive correlation observed with bivariate analysis is maintained. The common belief that the horse large intestinal parasite community is isolationist, due to the absence of negative pairwise interaction, is therefore contradicted by the present study., ((c) 2010 Elsevier B.V. All rights reserved.)