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Ophthalmologic and oculopathologic findings in red-tailed hawks and Cooper's hawks with naturally acquired West Nile virus infection

Amy M. PauliDepartment of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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Luis A. Cruz-MartinezThe Raptor Center, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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Julia B. PonderThe Raptor Center, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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Patrick T. RedigThe Raptor Center, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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Amy L. GlaserAnimal Health Diagnostic Laboratory, College of Veterinary Medicine, Cornell University, Ithaca, NY 14852

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Gia KlaussDepartment of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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James V. SchosterAnimal Eye Consultants of Minnesota, 1890 Brenner Ave, Roseville, MN 55113

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Arno WünschmannDepartment of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

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Abstract

Objective—To assess ophthalmologic features and ocular lesions in red-tailed hawks and Cooper's hawks naturally infected with West Nile virus (WNV).

Design—Original study.

Animals—13 hawks.

Procedures—All hawks underwent complete ophthalmic examinations including slit lamp biomicroscopy and binocular indirect ophthalmoscopy. Eleven hawks were euthanized because of a grave prognosis; complete necropsies were performed. Eyes, brain, heart, and kidneys were processed for histologic and immunohistochemical examinations. Pooled tissue homogenates and aqueous humor samples were assessed for WNV nucleic acid via PCR assay, and anti-WNV antibody titers in aqueous humor and plasma were determined.

Results—All birds had similar funduscopic abnormalities including exudative chorioretinal lesions and chorioretinal scarring in a geographic or linear pattern. Eleven birds were euthanized, and 2 birds were released. Plasma from both released hawks and plasma and aqueous humor of all euthanized hawks that were evaluated contained anti-WNV antibodies. Except for 1 hawk, all euthanized hawks had WNV-associated disease (determined via detection of WNV antigen or nucleic acid in at least 1 organ). Histopathologic ocular abnormalities, most commonly pectenitis, were detected in all euthanized birds; several birds had segmental choroiditis, often with corresponding segmental retinal atrophy. West Nile virus antigen was detected in the retinas of 9 of the euthanized birds. In 2 hawks, WNV antigen was detected in the retina only.

Conclusions and Clinical Relevance—Results indicated that funduscopically detectable chorioretinal lesions appear to be associated with WNV disease in hawks. Detection of ocular lesions may aid in antemortem or postmortem diagnosis of this condition.

Abstract

Objective—To assess ophthalmologic features and ocular lesions in red-tailed hawks and Cooper's hawks naturally infected with West Nile virus (WNV).

Design—Original study.

Animals—13 hawks.

Procedures—All hawks underwent complete ophthalmic examinations including slit lamp biomicroscopy and binocular indirect ophthalmoscopy. Eleven hawks were euthanized because of a grave prognosis; complete necropsies were performed. Eyes, brain, heart, and kidneys were processed for histologic and immunohistochemical examinations. Pooled tissue homogenates and aqueous humor samples were assessed for WNV nucleic acid via PCR assay, and anti-WNV antibody titers in aqueous humor and plasma were determined.

Results—All birds had similar funduscopic abnormalities including exudative chorioretinal lesions and chorioretinal scarring in a geographic or linear pattern. Eleven birds were euthanized, and 2 birds were released. Plasma from both released hawks and plasma and aqueous humor of all euthanized hawks that were evaluated contained anti-WNV antibodies. Except for 1 hawk, all euthanized hawks had WNV-associated disease (determined via detection of WNV antigen or nucleic acid in at least 1 organ). Histopathologic ocular abnormalities, most commonly pectenitis, were detected in all euthanized birds; several birds had segmental choroiditis, often with corresponding segmental retinal atrophy. West Nile virus antigen was detected in the retinas of 9 of the euthanized birds. In 2 hawks, WNV antigen was detected in the retina only.

Conclusions and Clinical Relevance—Results indicated that funduscopically detectable chorioretinal lesions appear to be associated with WNV disease in hawks. Detection of ocular lesions may aid in antemortem or postmortem diagnosis of this condition.

Contributor Notes

Dr. Pauli's present address is Veterinary Specialty and Emergency Care, 1848 Waldorf Blvd, Madison, WI 53719.

Presented in part at the 37th Annual Meeting of the American College of Veterinary Ophthalmologists, San Antonio, Tex, November 2006.

Address correspondence to Dr. Pauli.