1. Department of Virology and Immunology, Faculty of Veterinary Medicine, University of Liège, Institut de Chimie, Batiment B6, Local R80, Sart Tilman, 4000 Liège, Belgium
2. Centro Peruano de Estudios Cetológicos, c/o Grupo Cetáceos-Asociación de Ecología y Conservación, Casilla 1536, Lima 18, Peru
3. Department of Electron Microscopy, Pasteur Institute of Brabant, 45 rue Engeland, B-1180 Brussels, Belgium