1. Department of Parasitology and Tropical Veterinary Medicine, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht,1 and
2. Department of Parasitology, Faculty of Pharmacology, University of Granada, Campus Universitario de Cartuja, 18071 Granada, Spain2
3. Research Laboratory for Infectious Diseases, National Institute of Public Health and Environment, 3720 BA Bilthoven,3 The Netherlands, and