1. Department of Veterinary Clinical Studies,
2. Department of Veterinary Parasitology,
3. Wellcome Unit of Molecular Parasitology, Glasgow University, Bearsden Rd, Glasgow G61 1QH, Scotland, UK,
4. Lehrstuhl fur Tierzucht der Technischen Universitat Munchen, 85350, Freising, Weihenstephan, Germany