West Nile Virus Infection in Horses: Detection by Immunohistochemistry, In Situ Hybridization, and ELISA.
Authors: Toplu N, Oğuzoğlu T Ç, Ural K, Albayrak H, Ozan E, Ertürk A, Epikmen E T
Journal: Veterinary pathology
Summary
# Editorial Summary: West Nile Virus Detection and Pathology in Equine Cases Naturally occurring West Nile virus (WNV) infection presents variable clinical presentations in horses, necessitating reliable diagnostic methods and an understanding of pathological distribution within the nervous system. Researchers employed immunohistochemistry and in situ hybridization techniques on a naturally infected foal alongside serological testing (ELISA) on five additional horses displaying clinical signs consistent with WNV, establishing a cohort for comparative diagnostic evaluation. The deceased foal demonstrated characteristic pathological findings including oedematous and enlarged lymph nodes with intestinal congestion and focal haemorrhages, whilst histological examination revealed nonsuppurative meningoencephalomyelitis predominantly affecting the brainstem and spinal cord—regions where both viral RNA and antigen localised most intensely within nerve fibres, glial cells, and their processes. Notably, viral material was present to a lesser extent in the cerebral hemispheres and cerebellum, suggesting preferential tropism for lower central nervous system structures. For equine practitioners, these findings underscore that WNV neuropathology concentrates in clinically significant motor and sensory relay regions, which may explain the neurological signs observed in affected horses, and that confirmation requires advanced immunological or molecular techniques rather than clinical assessment alone, particularly when serological responses are still developing in acute infection.
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Practical Takeaways
- •WNV should be included in differential diagnosis for horses presenting with neurological signs, particularly those affecting the brainstem and spinal cord
- •Multiple diagnostic methods (immunohistochemistry, in situ hybridization, and serology) may be needed for definitive WNV diagnosis in affected horses
- •Awareness of WNV clinical presentation is important for early recognition and appropriate biosecurity measures on affected premises
Key Findings
- •WNV diagnosed in a foal via immunohistochemistry and in situ hybridization with nonsuppurative meningoencephalomyelitis as primary lesion
- •Five additional horses showed clinical signs of WNV infection with positive antibody detection by ELISA
- •Viral antigen and RNA concentrated in nerve fibers and glial cells of brainstem and spinal cord, with lesser involvement of cerebral hemispheres and cerebellum
- •Necropsy findings included edematous enlarged lymph nodes and diffuse intestinal congestion with focal hemorrhages