A sero-epidemiological survey on the occurrence of opisthorchiid liver flukes in red foxes ( Vulpes vulpes) in Berlin, Germany.

Serum samples collected from red foxes in the city of Berlin between 1996 and 1999 were analysed for the presence of antibodies against Opisthorchis felineus and Metorchis bilis using an indirect ELISA. Out of 1,000 specimens, 30.6% and 46.5% reacted positively with specific O. felineus and M. bilis antigens, respectively. Seroprevalence in adult foxes was always higher than in juveniles. While no significant differences were observed in adult foxes throughout the period, in juvenile specimens seroprevalence declined from 1996 to 1997, then stayed at a comparable level in 1998 and increased in 1999. A varying availability of fresh cyprinid fish in different years seems to be the reason for changes in seroprevalence. By grouping the samples from juvenile foxes by season, antibodies against both Metorchis and Opisthorchis antigens started to appear between April and June, increased between July and September()and reached a level comparable to adult foxes in the October to December quarter. The lowest seroprevalence was found in Pankow, which is the district with the lowest share of the surface water.