Nematode parasite eggs in pasture soils and pigs on organic farms in Sweden

The EU regulation for organic pig production requires outdoor access to promote the animal welfare. This may increase the risk of infection of the common pig parasites, Ascaris suum and Trichuris suis, because their eggs can survive for many years in the soil. The egg contamination of these parasites in outdoor areas with different managements and the faecal egg output from the pigs was investigated on 11 Swedish organic pig farms in 2008. We found eggs of A. suum and, to a minor extent, T. suis in the soil from outdoor areas, which had previously been used for pig rearing and/or for spreading of pig manure. Piglets and their dams were turned out on pastures included in a crop rotation, and these areas had a mean of 2500 A. suum and 40 T. suis eggs per kilogram soil. When the pigs were 12-week-old, the faecal egg counts (FECs) of A. suum were positively correlated with the egg concentration in pasture soils before pig turnout. The areas used by dry sows had a mean of 11,700 A. suum and 220 T. suis eggs per kilogram soil. The highest egg concentrations in the soil were found in areas, frequently used by pigs in the most recent years. To minimise pasture contamination with parasite eggs, it is advised to have a crop rotation system and to inactivate parasite eggs in pig manure before spreading it. Parasite control needs further development to protect suckling piglets from infections due to environmental parasite egg contamination. © 2019, The Author(s).Funding details: 1904; Funding details: Center for Outcomes Research and Evaluation, Yale School of Medicine, CORE; Funding text 1: The authors gratefully acknowledge the farmers for supplying data and opening up their farms for investigation and the funders for their financial support. This study comprises data from two different projects. Soil samples and crop rotation data were collected within a national project funded by the Swedish Board of Agriculture and faecal samples, and some farm data were collected within the COREPIG project (project no. 1904), one of the eight research projects selected for transnational funding by the partners of the CORE Organic ERA-net project (Sweden: Formas). We also wish to thank Sofia Wiberg for collecting samples and data within the latter project.