Marquis is an antiprotozoal oral paste prescribed for the treatment of equine protozoal myeloencephalitis (EPM). EPM is a devastating neurologic disease that leads to inflammation of the brain and spinal cord, resulting in various neurological deficits in horses such as abnormal gait, stumbling, falling, and an inability to rise. Horses get EPM by ingesting opossum feces that contain a parasite called protozoa Sarcocystis neurona. If the feed, grass, or water has been contaminated with the opossum's feces, the horses will ingest the parasite, which can cause neurological damage, including lesions on the spinal cord and brain stem. Marquis oral paste contains the active ingredient ponazuril, which crosses the blood/brain barrier to reach the central nervous system. Once it has reached the central nervous system, ponazuril kills the parasite and prevents it from causing further damage. Marquis is available on Vetito veterinary pharmacy in a ready-to-use syringe containing 127 grams of paste, which offers 7 days of treatment for a 1200 lb horse.