Numerous intermediate hosts that can complete the life cycle of S. neurona have been identified. A significant number of these hosts are killed on US freeways providing ample food sources for the opossum, leading to subsequent contamination of the environment. Prevention of equine protozoal myeloencephalitis should involve many factors but an important part of any prevention program should include management changes, which eliminate these as a source of infection for the definitive host. Authors’ addresses: Department of Veterinary Preventive Medicine, 1920 Coffey Road, Columbus, Ohio 43210-1092 (Saville); Department of Large Animal Clinical Sciences, 601 Vernon Tharp Dr., Columbus, OH 43210-1089 (Reed); United States Department of Agriculture, Parasite Biology, Epidemiology and Systematics Laboratory, Building 1001, Beltsville, MD 20705-2350 (Dubey). © 2002 AAEP.