Fumonisin B1 levels associated with an epizootic of equine leukoencephalomalacia.

During the fall of 1989, an episode of equine leukoencephalomalacia involved 18 of 66 purebred Arabian horses at a breeding/training stable in Arizona. Of the 18 horses affected, the condition was fatal in 14. These horses, as well as 48 unaffected horses, had been fed a diet containing a substantial amount of white corn screenings. Gross pathologic findings included liquefactive necrosis in parts of the cerebral white matter and hemorrhagic foci of various sizes in the brain stem. Histopathologic findings included rarefied white matter with pyknotic nuclei and eosinophilic cytoplasm. Thin-layer chromatography, high-performance liquid chromatography, and gas chromatography/mass spectroscopy were utilized to identify and quantitate fumonisin B1 in 3 samples of corn from the farm. Concentrations of fumonisin B1 range from 37 to 122 ppm. Fumonisin B2 was also detected. Using information on diet, animal weights, and feeding practices, estimates of total fumonisin B1 dosage were determined. This is the first definitive report on equine leukoencephalomalacia and associated fumonisin B1 concentrations.