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Volume 15, Number 6—June 2009

Research

Lineage 2 West Nile Virus as Cause of Fatal Neurologic Disease in Horses, South Africa

Marietjie VenterComments to Author , Stacey Human, Dewald Zaayman, Gertruida H. Gerdes, June Williams, Johan Steyl, Patricia A. Leman, Janusz Tadeusz Paweska, Hildegard Setzkorn, Gavin Rous, Sue Murray, Rissa Parker, Cynthia Donnellan, and Robert Swanepoel
Author affiliations: University of Pretoria, Pretoria, South Africa (M. Venter, S. Human, D. Zaayman, J. Williams, J. Steyl, C. Donnellan); National Health Laboratory Services, Pretoria (M. Venter); Onderstepoort Veterinary Research Institute, Pretoria (G.H. Gerdes); National Institute for Communicable Diseases, Johannesburg, South Africa (P. Leman, J.T. Paweska, R. Swanepoel); Chartwell Equine Clinic, Midrand, South Africa (H. Setzkorn); Karoo Veterinary Clinic, Colesburg, South Africa (G. Rous); Witbos Clinic, Midrand (S. Murray); Glen Austin Equine Clinic, Midrand (R. Parker)

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Table 2

Clinical findings, West Nile virus–infected horses, South Africa*

Case no. Age Clinical findings Outcome Postmortem findings Histopathologic findings
SAE12/07 5 y Neurologic signs, hind and fore limb ataxia, pupil miosis, head held to left Survived
SAE89/08 1 y Neurologic signs, hind and forelimb ataxia, fever, complete paralysis, anorexia, hepatitis Died (euthanized after week of fluid therapy) Postmortem not done
HS101/08 8 y Neurologic signs, severe ataxia especially hind limb, seizures and chewing, froth from mouth, fever, recumbency, paralysis Died Marked generalized subcutaneous edema involving trunk and proximal forelimbs, edema (periaortic, coronary grooves, neck, and hind quarters), partial pulmonary collapse, foam-filled trachea, mild serosanguinous hydrothorax, moderate hydropericardium, subpleural petechiae and ecchymoses, epicardial grooves and at bases of the mitral valves Lesions in gray matter and meninges of lumbar spinal cord (pericentral canal gliosis, edema, gray matter gliosis with occasional neuronal degeneration or death), mild perivascular cuffing with mononuclear cells and scattered neutrophils, moderate vascular congestion, occasional perivascular petechiae, mild leptomeningitis (mostly round cells) and occasional mild spinal ganglioneuritis, segmental mural necrosis of the dural blood vessels and neutrophil invasion, less-marked lesions in rest of spinal cord and white matter of midbrain
M123/08 4 mo Fever, neurologic signs, paralysis (Schiff-Sherington sign), rectal prolapse Died Severe perirenal and intermuscular edema, severe diffuse interlobular lung edema and mild serous hydropericardium Marked white matter lesions in peripheral lateral and ventromedial spinal cord white matter, mild perivascular round cell cuffing in midbrain, patchy spongiosis and gliosis in brain and cerebellum white matter
HS125/08 8 mo Neurologic signs, ataxia, mild colic, swollen head and neck Died (shot by owner) Severe lung edema and congestion, moderate serous hydropericardium, intermuscular edema Subtle lesions on brain and cerebellum sections (e.g., gliosis and spongiosis in white matter and vascular leukostasis)
SAE126/08 6 y Neurologic signs, head hanging, sick for week Died suddenly Spinal cord lesions
SAE134/09 19 y Neurologic signs, partial blindness, hyperexcitability, seizures Survived

*AHSV, African horse sickness virus; IHC, immunohistochemistry.

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