Institution: | 1. Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, , Gauteng, South Africa;2. Equine Research Centre, University of Pretoria, , Gauteng, South Africa;3. Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, , USA;4. Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, , USA |