1. Department of Veterinary Pathology of the Federal University of Rio Grande do Sul, Porto Alegre, Brazil
2. Laboratory of Virology, Department of Microbiology, Immunology and Parasitology, Institute of Basic Health Sciences of the Federal University of Rio Grande do Sul, Porto Alegre, Brazil
3. Hospital Veterinary Clinics of the Federal University of Rio Grande do Sul, Porto Alegre, Brazil
4. Department of Animal Medicine of the Federal University of Rio Grande do Sul, Porto Alegre, Brazil