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Prior to the beginning of the 90th, the occurance of opisthorchiid flukes in man and animals was proved only by sporadical findings in Germany. However, systematic investigations on red foxes as indicator hosts using classical parasitological methods showed that opisthorchiidosis is more spreaded than previously supposed. The aim of this study was the development of a serological test to detect specific antibodies against the most common liver flukes in foxes, 0. felineus and M bilis. Running two experimental series, eleven silver foxes were infected with opisthorchiid metacercariae per os. These metacercariae were isolated from experimental and natural infected cyprinid fish. Serum samples were collected prior infection and in weekly, later in monthly intervals post infection. At identical occasions samples of feces were examined in order to determine the status of endoparasites using the MIFC-technique. Plasma samples were monitored for liver-enzyme activities.Dialysed excretory- and secretory products of in vitro cultivated adult 0. felineus and M bilis respectively were used as antigens in an indirect ELISA. Dog-IgG was used as the conjugate. Determined by checkerboard-titration, the suitable antigen dilution was 1:25 and 1:40 for 0. felineus and M bilis respectively. The appropriate scrum dilution was 1:100. Altogether 190 sera from liver fluke free farm foxes were used to establish the cutoff. Depending on the fluke species and the infection dose used, seroconversion against the homologue antigen occurred between the 2nd and 5th week post infection. After reaching the peak-level antibody concentration persisted at a plateau phase and declined slightly at the end of observation. In contrast, the heterologue antigen didn"t react at all or, in some cases, reacted weakly indicated by low ELISA-indices at later dates. As an explanation for this the different antigen structures of both flukes represented by different bands in SDS-PAGE can be considered.All infected foxes excreted opisthorchiid eggs after a prepatent period of 2 to 4 weeks. The duration of excretion was individually different. Except of one fox killed in die 1 11th week postinfection dissection of the others carried out between the 33th and 42th week post infection showed a low burden and two foxes were negative for flukes at all.Differences in the activity of liver enzymes were depending on infection dose and fluke species. Already during the prepatent period ferment activities showed a first peak.A dilatation of the bile ducts was the dominating pathomorphological picture in infected animals. The bile duct walls were hickened and the epithelium was distented like warts. The histopathological picture showed hypertrophy and hyperplasia of the bile duct epithelium.The conclusion of this study is, that the newly developed ELISA using excretory/secretory antigens is able to detect antibodies against opisthorchiid flukes. It seems to be a suitable method to carry out seroepidemiological surveys.