1. Department of Animal Supply and Laboratory for Parasitology and Mycology, National Institute of Public Health and Environmental Protection, PO Box 1,3720 BA Bilthoven, The Netherlands
2. Laboratory for Bacteriology, National Institute of Public Health and Environmental Protection, PO Box 1,3720 BA Bilthoven, The Netherlands
3. Laboratory for Pathology, National Institute of Public Health and Environmental Protection, PO Box 1,3720 BA Bilthoven, The Netherlands