The Experimental Induction of Leukoencephalomyelopathy in Cats

Abstract

Abstract. 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.

Scientific Opinion on the Chemical Safety of Irradiation of Food

“…One third of the cats (190 out of 540) in a colony were affected (Cassidy et al, 2007), whereas in another experiment all cats fed with irradiated diet became ataxic with the severity of the symptoms in correlation with the period of feeding irradiated diet (Caulfield et al, 2009). Many of the cats that became paraplegic did recover after > 2 months but cats that became tetraplegic did not recover completely.…”

“…Four publications (Cassidy et al, 2007;Caulfield et al, 2009;Duncan et al, 2009;Child et al 2009) relate leukoencephalomyelopathy (LEM) in cats with the feeding of highly irradiated diet. There are controversies regarding the effects of irradiation and why irradiated feed causes LEM in cats.…”

“…Researchers tried to reproduce the observed effects experimentally in two studies (Caulfield et al, 2009;Duncan et al, 2009). In the Caulfield et al (2009) study the disease was reproduced in male cats.…”

“…In the Caulfield et al (2009) study the disease was reproduced in male cats. Female cats were not used.…”

“…A change in diet, nursing care, physiotherapy and time seem to be the only factors common in recovered cats. Caulfield et al (2009) tried to induce experimentally the disease by long-term feeding SPF cats with a gamma-irradiated diet. Thirty-one clinically and neurologically normal, male SPF cats of between 6 and 14 months of age and between 3.1 to 6.6 kg bw were randomized into 4 treatment groups.…”