1. Department of Wildlife, National Veterinary Institute, SE-751 89 Uppsala, Sweden
2. Current address: Center for Fish and Wildlife Health, Institute of Animal Pathology, Vetsuisse Faculty, University of Berne, Postfach 8466, CH-3001 Berne, Switzerland
3. Department of Parasitology (SWEPAR), National Veterinary Institute and Swedish University of Agricultural Sciences, SE-751 89 Uppsala, Sweden