1. Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0342
2. Faculty of Veterinary Medicine, University of Montreal, St-Hyacinthe, Quebec, Canada
3. Centro de Diagnostico Integral, Instituto Technologico de Sonora-UGRPS, Sonora, Mexico
4. Investigacion Aplicada, S.A. de C.V., Laboratorio de Biologia, Tehuacan, Puebla, Mexico