Distribution of eastern equine encephalomyelitis viral protein and nucleic acid within central nervous tissue lesions in white-tailed deer (Odocoileus virginianus).
Authors: Kiupel M, Fitzgerald S D, Pennick K E, Cooley T M, O'Brien D J, Bolin S R, Maes R K, Del Piero F
Journal: Veterinary pathology
Summary
# Eastern Equine Encephalomyelitis in White-Tailed Deer: Neuropathological Distribution and Diagnostic Implications During a 2005 outbreak in Michigan, researchers examined brain tissue from seven free-ranging white-tailed deer confirmed positive for eastern equine encephalomyelitis (EEE) virus using reverse transcriptase polymerase chain reaction, employing detailed microscopic analysis alongside immunohistochemistry and in situ hybridization techniques to map viral distribution and characterise the resulting lesions. All affected deer displayed polioencephalomyelitis with leptomeningitis, concentrated in the cerebral cortex, thalamus, hypothalamus, and brainstem; three animals additionally showed microhemorrhages around smaller vessels, though frank vasculitis was absent, whilst neuronal necrosis with perineuronal satellitosis and neutrophilic neuronophagia proved most severe in the thalamus and brainstem. Viral protein labelling occurred predominantly within neuronal soma, axons and dendrites of both damaged and healthy neurons, with notably less involvement of glial cells and minimal presence in the cerebellum and hippocampus, whilst viral nucleic acid appeared exclusively in neuronal cytoplasm with a comparable distribution pattern. These findings establish that EEE produces a characteristic, regionally-specific neuropathological signature in cervids that distinguishes it from presentations in equine and other species, necessitating inclusion of EEE in the differential diagnosis for neurological disease and meningoencephalitis in white-tailed deer populations—particularly relevant for practitioners monitoring wildlife health or managing deer in endemic areas.
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Practical Takeaways
- •EEE should be considered in differential diagnosis when evaluating neurologic disease in free-ranging white-tailed deer populations, particularly during late summer and fall
- •The characteristic neuropathological pattern of viral localization in neurons of the thalamus and brainstem can aid in post-mortem diagnosis using immunohistochemistry and in situ hybridization techniques
- •Wildlife professionals managing deer populations during EEE outbreaks should recognize neurologic signs as a clinical indicator of disease presence in the herd
Key Findings
- •All 7 deer with EEE showed polioencephalomyelitis with leptomeningitis predominantly affecting cerebral cortex, thalamus, hypothalamus, and brainstem
- •Viral protein localized primarily in neuronal perikaryon, axons, and dendrites with minimal involvement of glial cells
- •Neuronal necrosis with perineuronal satellitosis and neutrophilic neuronophagia was most prominent in thalamus and brainstem
- •In situ hybridization labeling was exclusively observed in neuronal cytoplasm with distribution pattern matching immunohistochemistry findings