Determining the biological activity of helminth eggs, comprises: (a) determining the stages of embryonic development of helminth eggs; (b) determining the metabolic activity of embryonated helminth eggs; (c) determining the inducibility of the gene expression in embryonated helminth eggs; (d) microscopically determining the motility of helminth larva present in the egg, and/or determining the hatching from helminth larva in the subject, where the intact embryonated helminth eggs recovered from intestinal contents are quantified in comparison to an internal standard. Determining the biological activity of helminth eggs, comprises: (a) determining the stages of embryonic development of helminth eggs using quantitative PCR-analysis and marker sequences for determining the copy number of the genomic DNA; (b) determining the metabolic activity of embryonated helminth eggs using biochemical and/or molecular biological methods; (c) determining the inducibility of the gene expression in embryonated helminth eggs; (d) microscopically determining the motility of helminth larva present in the egg over long observation period after the pre-incubation at increased temperatures, and/or determining the hatching from helminth larva in the subject, where the intact embryonated helminth eggs recovered from intestinal contents are quantified in comparison to an internal standard. An independent claim is included for helminth eggs, which are at least 50% biologically active, determined by the above method, and the embryonic development is continued. ACTIVITY : Immunosuppressive. No biological data given. MECHANISM OF ACTION : None given.