The experimental induction of leukoencephalomyelopathy in cats.

Leukoencephalomyelopathy of undetermined etiology has been described in specific pathogen-free cats. A study was established to assess if the long-term feeding of a gamma-irradiated diet could induce this disease. Cats fed exclusively on diet irradiated at 25.7-38.1 kGy ("typical" dose) and 38.1-53.6 kGy (high-end dose), respectively, developed typical lesions with attendant, progressively severe ataxia between study days 140 and 174. The onset of ataxia at day 140 and the number of animals affected at this time were similar in animals fed each ration. A maximum ataxia "score" was first reached by an animal on the high-end dose diet on day 167 and by 2 cats fed the "typical-end" dose diet 21 days later. Ataxic cats and 1 animal euthanized on day 93 prior to the onset of ataxia exhibited varying degrees of Wallerian degeneration in the spinal cord and brain, similar to the spontaneous disease. The elevated total antioxidant status of spinal cord segments and hepatic superoxide dismutase concentration of cats fed typical and high-end treated diets suggested free-radical involvement in the pathogenesis. The significantly elevated peroxide concentrations of the irradiated diets (1,040% and 6,440% of untreated values) may have resulted in increased oxidative insult, a factor possibly exacerbated by the treated diets' reduced vitamin A content. This study has reproduced leukoencephalomyelopathy in cats similar to spontaneous outbreaks by feeding a gamma-irradiated dry diet with elevated peroxide and reduced vitamin A concentrations.