Cerebrospinal Nematodiasis with Focal Encephalomalacia as a Cause of Paralysis of Beavers ( Castor Canadensis ) in the Dublin Zoological Gardens

SUMMARY Fatal paralysis has occurred in beavers in the Dublin Zoological Gardens for some years, and it has been found impossible to raise this species to maturity. Immature worms or larvae which are probably ascarids appear to be the cause of a focal malacia of the brain and almost certainly account for the neuroparalytic signs. We have no idea what are the natural hosts of these parasites. The case adds to a growing list of diseases which are caused by helminth parasites migrating to the central nervous system of a great variety of mammalian hosts.