Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/15/2000
Publication Date: N/A
Citation: Interpretive Summary: Raccoons 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. Under free ranging situation, these animals may get access to animal carcasses that may have died of naturally occurring transmissible spongiform encephalopathies (TSEs) such as scrapie, transmissible mink encephalopathies (TME), and chronic wasting disease (CWD). Experimental evidence indicates that raccoons can be readily infected by TME. Also the incubation period in these studies was found to be relatively short (6-10 months), compared to over 2 years for scrapie in sheep or in mice. Therefore, raccoons can be considered as useful experimental animal models for the study of TSEs of livestock. However, since there is paucity of published information on diseases of raccoons (especially those affecting the brain), documentation of naturally occurring diseases and lesions in this species is of paramount importance. In the present study, we examined brains of 53 raccoons from Parramore Island, Virginia, USA and found microscopic evidence of multifocal mineralizations (psammoma bodies) in 33/53 (62%) raccoons. In most cases the affected vessels appeared to have been completely occluded. Since this condition is observed in brains of many normal raccoons, it should be considered as incidental finding and, therefore, should be differentiated from any experimental disease that is being transmitted to this species.
Technical Abstract: Microscopic evidence of multifocal mineralizations (psammoma bodies) were seen in brains of 33/53 (62%) raccoons (Procyon Lotor) necropsied on Parramore Island, Virginia, USA. Most mineralized foci had concentric laminations and were present in small capillaries of meninges of the brain (15/33), in choroid plexus (3/33), or at both these sites (13/33). In two raccoons the lesions were confined to the meninges of the proximal cervical spinal cord. In most cases the affected vessels appeared to have been completely occluded. However, no evidence of ischemic changes in the brain parenchyma was seen and none of the raccoons had abnormal neurologic signs prior to euthanasia. The condition appears to be a common incidental histopathological finding in raccoons from the eastern United States. Although the exact cause of this condition is not known, a primary vascular insult with resultant dystrophic mineralization of the affected vessels is suspected.