1. Department of Biology, Arizona State University, P.O. Box 871501, Tempe, Arizona 85287-1501, USA
2. Department of Pathobiology, University of Florida, P.O. Box 110880, Gainesville, Florida 32611-0880, USA
3. School of Veterinary Science, Universitat Autonoma de Barcelona, 08193 Bellaterra (Barcelona), SPAIN