1. Department of Microbiology; Carver College of Medicine; Iowa City; IA; USA
2. Virus and Prion Disease Unit; National Animal Disease Center; USDA-ARS; Ames; IA; USA
3. Curso de Medicina Veterinaria; Campus Universitario do Bairro Sao Jose; Universidae de Passo Fundo; Fundo; RS; Brazil