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9 April 2019 PRESUMED PHOTORECEPTOR DYSPLASIAS IN PEREGRINE FALCONS (FALCO PEREGRINUS) AND PEREGRINE FALCON HYBRIDS
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Abstract

We describe a case series of photoreceptor dysplasia with secondary retinal degeneration in juvenile Peregrine Falcons. Six Peregrine Falcons (Falco peregrinus) and three Peregrine Falcon × Prairie Falcon (Falco mexicanus) hybrids had early-life visual deficits. Eight birds had visual defects shortly after hatching, and one bird had visual deficits first noticed at 5 mo of age. Complete ophthalmic examinations were performed in each animal. Eight of the animals had electroretinograms, and nine of the animals had their eyes examined histologically after euthanasia. Ophthalmic examinations did not reveal consistent and potentially blinding abnormalities, including an absence of ophthalmoscopic retinal lesions. Electroretinographic findings included subnormal amplitudes (with rod responses more abnormal than cone responses), with a negative b-wave amplitude occurring in one bird. Histologically, a reduction in the number of photoreceptors was present with numerous degenerative changes to the remaining photoreceptors, including frequent blunting and disorganization of photoreceptor outer segments, decreased numbers of cells in the inner nuclear layer, decreased numbers of ganglion cells, decreased thickness of the nerve fiber layer, and decreased myelinated axons within the optic nerve. Ultrastructurally, only minor cone outer segment changes and occasional phagocytic cells were seen. Results strongly suggested a primary retinopathy, characterized by photoreceptor dysplasia and secondary retinal degeneration with loss of cellular elements throughout the retina. The presence of a similar spectrum of findings in related individuals, the early age of onset, and the relative lack of other environmental, ocular, or systemic abnormalities suggested possible heritability.

© Wildlife Disease Association 2019
Bret A. Moore, Christopher J. Murphy, Annajane Marlar, Richard R. Dubielzig, Leandro B. C. Teixeira, William T. Ferrier, and Steven R. Hollingsworth "PRESUMED PHOTORECEPTOR DYSPLASIAS IN PEREGRINE FALCONS (FALCO PEREGRINUS) AND PEREGRINE FALCON HYBRIDS," Journal of Wildlife Diseases 55(2), 325-334, (9 April 2019). https://doi.org/10.7589/2018-02-055
Received: 25 February 2018; Accepted: 23 June 2018; Published: 9 April 2019
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