1. Department of Parasitology, Leiden University Medical Centre, Leiden 2333 ZA, Netherlands
2. Trudeau Institute, Saranac Lake, NY 12983
3. Department of Pathology, University of Cambridge, Cambridge CB2 1QP, England, UK
4. School of Biology, University of Nottingham, Nottingham NG7 2RD, England, UK
5. Research Center Borstel, Borstel 23845, Germany