Neural Larva Migrans Due to Baylisascaris procyonis in Captive Lovebirds and Lorikeets: A Case Series
American Association of Zoo Veterinarians Conference 2005
Deanna Russell1,2, BSc, MD, DVM; Dale Smith1, DVM, DVSc; Graham Crawshaw2, BVetMed, DACZM; Chris Dutton2, BSc, BVSc, MSc, MRCVS; Rolf Arne-Olberg5, DVM, DVSc; Mads Bertelson4, DVM, DVSc; Karrie Rose5, DVM, DVSc
1Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada; 2Toronto Zoo, Scarborough, ON, Canada; 3Kristiansand Dyrepark, Kristiansand, Norway; 4Copenhagen Zoo, Frederiksberg, Denmark; 5Veterinary and Quarantine Centre, Taronga Zoo, Mosman, NSW, Australia
Neural larva migrans (NLM) has been identified as a cause of neurologic disease in parrots housed outdoors (seasonally) at the Toronto Zoo. Between August and October 1994, nine peach-faced lovebirds (Agapornis roseicollis) developed neurologic signs including head tilt, circling, nystagmus, loss of balance, incoordination, weakness, and extensor rigidity. Affected lovebirds had histologic lesions within the brain and/or spinal cord that included leukomalacia, axonal degeneration, and/or perivascular lymphoplasmacytic cuffing. Since June 2002, 14 of 41 green-naped (Trichoglossus haematodus haematodus) and Swainson’s (Trichoglossus haematodus moluccanus) lorikeets developed similar neurologic signs and histologic lesions to those seen in the lovebirds. Three lorikeets also had histologic evidence of Baylisascaris procyonis larvae within the brain. This case series demonstrates the difficulty in identifying the etiology of neurologic disease in parrots. The sole method of establishing a definitive diagnosis of NLM due to B. procyonis is through identification of larvae in tissue.1 Only three of the 23 cases reported in this case series had larvae present histologically. In the absence of histologic confirmation of larvae, the diagnosis of NLM is strongly suggested if several criteria are met. These include a history of exposure (directly or indirectly) to scat from raccoons infected with B. procyonis, characteristic neurologic signs, and the presence of leukomalacia in central nervous system tissue.2 Confirming exposure to infective B. procyonis eggs can be difficult since the eggs persist in the environment for years and may not be associated with scat. Treatment was ineffective in the cases described, which highlights the importance of prevention.
1. Kazacos, K.R., and W.M. Boyce. 1989. Baylisascaris larva migrans. J. Am. Vet. Med. Assoc. 195:894–903.
2. Kazacos, K.R. 2001. Baylisascaris procyonis and related species. In: Samuel, W.M., Pybus, M.J., and A.A. Kocan, eds. Parasitic Diseases of Wild Mammals. Iowa State University Press, Ames, IA. Pp. 301–341.