Objective: To evaluate CSF in horses with confirmed West Nile virus encephalomyelitis.
Design: Retrospective study.
Animals: 30 horses.
Procedure: Results of CSF analyses from horses with acute neurologic signs attributed to West Nile virus infection that was confirmed by immunoglobulin M antibody capture ELISA were reviewed and analyzed.
Results: Among 30 CSF samples, findings in 8 (27%) were within reference ranges and in 22 (73%) were abnormal. Among the 22 abnormal samples, mononuclear pleocytosis was found in 16 (73%) and high protein concentration with nucleated cell count within reference range was found in 6 (27%) samples. A predominance of lymphocytes was found in 11 of 16 samples with mononuclear pleocytosis, and a predominance of large mononuclear cells was found in 5 of 16 samples. Sensitivities of analyses of CSF obtained from the lumbosacral and atlanto-occipital regions of the spinal cord were 89 and 50%, respectively.
Conclusions and clinical relevance: Results suggest that in horses with acute onset of neurologic signs caused by West Nile virus encephalomyelitis, findings in the CSF are likely to be abnormal, mononuclear pleocytosis with lymphocytic predominance may be most commonly observed, and CSF collected from the lumbosacral region may be abnormal more commonly than CSF collected from the atlanto-occipital region.