Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

of the rumen and gets into the liver, where it undergoes sulfonation or sulfoxigenation during the detoxification processes. The metabolites get into the plasma, from where they rediffuse into the gastrointestinal tract where they exert their effect (Takáts 1986). MATERIALS AND METHODS The studies were conducted in the "János Xantus" zoo of Győr. The data of animals included in the experiments are shown in Table 2. Table 2 Data of animals included in the study Species Age (years) Sex Number Lama glama 4-10 female 4 (2 pregnant) Lama glama 1/2-1 male 2 Lama glama 7-10 male 1 Bison bison 7 female 2(pregnant) Bison bison 7 male 1 Bison bison 4 male 1 Bison bonasus 7 female 1 Bison bonasus 7 male 1 Bos taurus primigenius hungaricus 7 female 1 (pregnant) Bos taurus primigenius hungaricus 1/2 male 1 Bos taurus primigenius hungaricus 7 male 1 Keeping of the animals The bisons were kept in pairs (one bull and one cow) in adjacent pens. (However, when cleaning the pens, the following routine was followed: the 4 American bison were driven into a run and the European bison were driven to their place; in this way, one run was always empty, and bedding, manure removal and feeding could be done easily). The pair of Hungarian Grey cattle was kept adjacent to the bison. The llamas were kept in a joint pen (however, they were often let out into a larger run, together with other herbivorous animals including deer, Cameroon dwarf goats, a Hungarian halfbred mare, and ponies). Nematode infection and its therapy Spontaneously excreted faecal samples were collected from the ground into plastics jars, in two series: the first series lasted from 4 May 1990 to 5 July 1990 and the second from 5 October 1990 to 11 December 1990. In order to determine the prevalence of nematode infection, the samples collected before medication (on day -7 and day 0) were examined by Fülleborn's method as follows.