Avian Bornavirus Infection in Free-Ranging Waterfowl: A Retrospective and Prospective Study
Pauline Delnatte1,2, DVM; Davor Ojkic3, DVM, MSc, PhD; Josepha DeLay3, DVM, DVSc, DACVP; Eva Nagy1, DVM, PhD, DSc; Doug Campbell4, DVM, DVSc; Graham Crawshaw2, BVetMed, MRCVS, DACZM; Dale A Smith1, DVM, DVSc1
1Ontario Veterinary College, University of Guelph, Guelph, ON, Canada; 2Toronto; Zoo, Toronto, ON, Canada; 3Animal Health Laboratory, University of Guelph, Guelph, ON, Canada; 4Canadian Cooperative Wildlife Health Centre, Guelph, ON, Canada
A new strain of avian bornavirus (ABV) has been recently identified as a cause of neurologic disease and mortality in free-ranging Canada geese (Branta canadensis) and trumpeter swans (Cygnus buccinator) in Southern Ontario.1 A retrospective evaluation of pathology cases from wild waterfowl euthanatized or found dead on the Toronto Zoo site or submitted to the Canadian Cooperative Wildlife Health Centre, Ontario (1992–2011) was carried out. The presence of virus in tissues as assessed by immunohistochemistry and qRT-PCR was highly correlated with histologic lesions resembling those described in parrots affected with proventricular dilation disease. RT-PCR products were sequenced and their nucleotide sequences were 100% identical amongst themselves. Although ABV has been identified in apparently healthy geese, our study confirmed that ABV can also cause disease (clinical signs and pathologic lesions) in wild waterfowl species.2 In addition, cloacal swabs and blood samples were collected from 600 free-ranging Canada geese, trumpeter swans, mute swans (Cygnus olor) and mallard ducks (Anas platyrhynchos) to estimate the prevalence of ABV infection in Ontario. We found a 14% prevalence of fecal shedding (qRT-PCR) in geese caught on the Toronto Zoo site compared to a 0% prevalence in geese sampled at three other locations in Ontario. The prevalences of shedding of ABV in mute swans and trumpeter swans were 9% and 0%, respectively, despite the fact that these species commingle. The reason for these differences among species and locations is currently unknown. The waterfowl strain of ABV appears broadly distributed with the ranges of the susceptible species and has likely been endemic within North America for a substantial period of time.
The authors thank the Ontario Trumpeter Swan Re-introduction Program, the Canadian Wildlife Service and the Ministry of Natural Resources for assistance in collecting samples. Thanks to the Toronto Zoo, OMAFRA, CCWHC, Ontario and the Ontario Veterinary College (OVC) Pet Trust for financial support. We also thank the staff and students of Toronto Zoo, CCWHC, Animal Health Laboratory and of the virology laboratory of the OVC for help with this project.
1. Delnatte, P., C. Berkvens, M. Kummrow, D.A. Smith, D. Campbell, G. Crawshaw, D. Ojkic, and J. DeLay. 2011. New genotype of avian bornavirus in wild geese and trumpeter swans in Canada. Vet Rec. 169:108.
2. Payne, S., L. Covaleda, G. Jianhua, S. Swafford, J. Baroch, P. J. Ferro, B. Lupiani, J. Heatley, and I. Tizard. 2011. Detection and characterization of a distinct bornavirus lineage from healthy Canada geese (Branta canadensis). J Virol. 85:12053–12056.