Prevalence and magnitude of helminth infections in organic layinghens (Gallus gallus domesticus) across Europe

tHelminths are associated with health- and welfare problems in organic laying hens. The present observa-tional cross-sectional study therefore aimed to estimate the prevalence and worm burdens of intestinalhelminths in organic flocks of laying hens in 8 European countries, and to identify management factorsthat might be associated with helminth infections, with emphasis on Ascaridia galli. Data on flock-levelmanagement factors (e.g. nutritional factors, litter quality, housing system, opening- and closing hoursof popholes, pasture rotation and provision of occupational materials) were collected during a farm visitwhen the hens were on average 62 weeks old. Worm counts were performed for 892 hens from 55 flocksand the number of ascarid (presumably primarily A. galli) eggs per g faeces (EPG) for 881 hens from54 flocks. The association between parasitological parameters (prevalence, worm burden and EPG) andthe management factors were analysed by multivariate models. Results showed that A. galli was highlyprevalent across Europe with an overall mean prevalence of 69.5% and mean worm burden of 10 wormsper hen. The overall mean prevalence and worm burden for Heterakis spp. were 29.0% and 16 worms perhen, respectively, with a large variation between countries. On average, the hens excreted 576 ascaridEPG. The mean prevalence of Raillietina spp. was 13.6%. A positive correlation was found between meanA. galli worm burden and ascarid EPG. Of the analysed management factors, only pasture access timehad a significant negative association with A. galli worm burden which was in contrast to the generalbelief that outdoor access may increase the risk of helminth infections in production animals. In conclu-sion, the complexity of on-farm transmission dynamics is thus a challenge when evaluating the relativeimportance of management factors in relation to helminth infections.