Neuronal vacuolation in raccoons from Oregon

During a 2-year period (1995-1997), vacuoles were detected in neurons of 21 /50 (42% prevalence) raccoons (Procyon lotor) in Oregon. Age or sex predisp osition was not apparent. Twenty of these raccoons were from within a radiu s of 40 km of Corvallis in western Oregon. Microscopically, the vacuoles we re variable in size, were in the perikarya, and were consistently present i n pontine nuclei. Brain tissues were negative for rabies virus antigen by f luorescent antibody test and for the protease-resistant protein prion by im munohistochemistry. Electron microscopic examination of the brain stem of s elected animals revealed accumulation of electron-dense material within neu ronal perikarya. Light and electron microscopic examination indicated that the accumulated intracellular material had a high lipid content. These lesi ons suggest a form of neuronal storage condition. Further research is requi red to identify the composition of the intracellular lipid material, to elu cidate the mechanism of neuronal vacuolation in raccoons, and to understand the basis for the apparent geographic restriction of this lesion.