Neuronal Vacuolation in Raccoons from Oregon

Abstract

Abstract. During a 2-year period (1995)(1996)(1997), vacuoles were detected in neurons of 21/50 (42% prevalence) raccoons (Procyon lotor) in Oregon. Age or sex predisposition was not apparent. Twenty of these raccoons were from within a radius of 40 km of Corvallis in western Oregon. Microscopically, the vacuoles were variable in size, were in the perikarya, and were consistently present in pontine nuclei. Brain tissues were negative for rabies virus antigen by fluorescent antibody test and for the protease-resistant protein prion by immunohistochemistry. Electron microscopic examination of the brain stem of selected animals revealed accumulation of electron-dense material within neuronal perikarya. Light and electron microscopic examination indicated that the accumulated intracellular material had a high lipid content. These lesions suggest a form of neuronal storage condition. Further research is required to identify the composition of the intracellular lipid material, to elucidate the mechanism of neuronal vacuolation in raccoons, and to understand the basis for the apparent geographic restriction of this lesion.Raccoons (Procyon lotor) are nocturnal and are widespread throughout North America. They are highly adaptable omnivores and have managed to survive and increase their numbers in many urban and suburban areas. For this reason, they have been used as monitors of zoonotic diseases and environmental contamination. 2,7 Spongiform changes affecting the neuropil and neuronal cell bodies have been described in experimental and natural cases of rabies in skunks and foxes 3 and in a heifer. 5 Neuronal perikaryonic vacuolation is also seen in scrapie and related spongiform encephalopathes 6 and in lysosomal and acquired storage diseases of various animals. 11 Naturally occurring transmissible spongiform encephalopathy and storage diseases have not been documented in raccoons, but rabies is commonly encountered in raccoons of the eastern United States. However, vacuolation of neurons or the neuropil has not been seen in raccoons with naturally acquired rabies 9 or in raccoons experimentally infected with either a dog or a raccoon isolate of the rabies virus. 10 Recently vacuolation in neurons of 2 raccoons from 2 different geographic locations in the USA has been described. 8 Here, we describe histopathologic changes in 21 additional raccoons from the same geographic area of Oregon from which 1 of the original cases was identified. 9 Materials and methodsDuring a 2-yr period (Nov 1995-Oct 1997, 67 raccoons were examined at Corvallis, Oregon (USA; 44Њ34ЈN, From the College of Veterinary Medicine, Oregon State University, Magruder Hall, Corvallis, OR 97331.Present address: National Animal Disease Center, 2300 Dayton Road, Ames, IA 50010 (Hamir).Received for publication June 8, 1998. 123Њ16ЈW) to document baseline pathologic findings. The raccoons were found dead on highways (roadkills, n ϭ 40), were submitted as rabies suspects (n ϭ 2), or were obtained from local wildlife control organizations (n ϭ 25). Those from...

Nonlesions, Unusual Cell Types, and Postmortem Artifacts in the Central Nervous System of Domestic Animals

“…In raccoons (Procyon lotor), neuronal vacuolation has been described in various brainstem nuclei and cerebral neurons without obvious clinical disease. 51 Spheroids. Focal swellings of axons are commonly referred to as spheroids.…”

Spontaneous Spongiform Brainstem Degeneration in a Young Mouse Lemur (Microcebus murinus) with Conspicuous Behavioral, Motor, Growth, and Ocular Pathologies

“…to occur due to a variety of metabolic defects 17 as well as in geriatric animals. 14,20 A case of spontaneous transmissible spongiform encephalopathy in a 4-y-old rhesus monkey potentially originated from cross-species transmission through contaminated feed, 3 similar to the mechanism suggested for bovine spongiform encephalopathy; spontaneous spongiform degeneration in the brainstem of a NHP has not otherwise been described to date. In our mouse lemur, immunohistochemistry did not reveal any deposition of pathologic prion protein, and foodborne transmission of prions is highly unlikely, given our lemur's young age and the fact that no other animal in the colony had any clinical signs.…”

Focal epilepsy with fear‐related behavior as primary presentation in Boerboel dogs

“…However, canids appear to be resistant to prion diseases, and no cases of TSE in dogs have been published . Large cytoplasmic vacuoles in neurons have sporadically been described in non‐TSE conditions in animals, including rabies and disorders of unknown etiology . They often are associated with progressive neurological disease and a poor prognosis.…”