West Nile Virus Infection in Horses

Abstract

This study describes the clinicopathologic findings in naturally occurring West Nile virus (WNV) infection in horses. WNV was diagnosed in a foal by immunohistochemical and in situ hybridization methods, and the presence of WNV antibodies was detected in 5 other horses with clinical signs suggestive of WNV infection. At necropsy of the foal, lymph nodes were edematous and enlarged, and the intestines showed diffuse congestion and focal hemorrhages. The most significant histologic lesions in this case were nonsuppurative meningoencephalomyelitis, particularly in the brainstem and spinal cord. Identification of viral RNA by in situ hybridization and viral antigen by immunohistochemistry was concentrated primarily in nerve fibers, glial cells, and their processes in brainstem and spinal cord and, to a lesser extent, within the cerebral hemispheres and cerebellum.

Pathological features of West Nile and Usutu virus natural infections in wild and domestic animals and in humans: A comparative review

“…However, cerebrum can also be a target for WNV, as reported in some birds [35]. A multifocal lymphoplasmcytic myelitis of variable severity has been reported in birds [32,72], some mammals and in reptiles [44][45][46][47]49,51,57,74,76,78,79]. WNV antigen is seen in the cerebrum and cerebellum of both birds and mammals, mainly in the cytoplasm of neurons [3,17,19,28,29,32,34,35,[47][48][49]51,56,72] and glial cells [3,17,19,28,29,32,51,72].…”

“…Hepatic gross lesions including hepatomegaly [35,57,72], tan discoloration [35,57] and petechiae [35] are reported in birds and reptiles. Microscopically, randomly distributed necrosis is the main finding [9,17,57,72], while a defined pattern of midzonal necrosis is reported in horses [46]. Birds [9,[18][19][20]24,28,31,34,35] and some mammals [55,77] show a lymphoplasmacytic hepatitis with periportal or random distribution.…”

“…Microscopically, the most common finding is necrosis with a periarteriolar arrangement [9,19,72], followed by red and white pulp hyperplasia and lymphoid apoptosis [9,19]. Occasionally, splenitis with a mixed inflammatory cell population, including heterophils [35,54,72] is seen in birds and horses [46] and in alligators [57]. As for vascular lesions, fibrino-necrotizing arteritis is reported.…”

Validating Immunohistochemistry Assay Specificity in Investigative Studies: Considerations for a Weight of Evidence Approach

“…The correlation of labeling between the 2 assays adds confidence in the specificity of the labeling. 47 Similarly, detection of ETV1 protein in the mouse cerebral cortex by IHC and transcript by ISH increases the confidence in each individual assay (Fig. 13).…”

West-Nil-Virus-Infektion bei 12 Pferden in Mitteldeutschland

“…Hinsichtlich der neurologischen Symptomatik betreffen WNV-Infektionen vor allem die graue Substanz des Hirnstamms mit Medulla oblongata und Pons sowie die graue Substanz der ventralen Anteile des Rückenmarks im Bereich der Brust- und Lendenwirbelsäule 34 , 35 , allerdings können Gehirn und Rückenmark variabel in ihren Abschnitten betroffen sein. Als typisches histopathologisches Korrelat sind perivaskuläre lymphohistiozytäre Infiltrate in den betroffenen Abschnitten beschrieben (Encephalomyelitis), die von Mikrogliosen, einer variablen Anzahl von neutrophilen Granulozyten und perivaskulären Blutungen begleitet sein können 34 , 36 , 37 . Vergleichbare Befunde fanden sich auch im Rahmen der bei Pferd 9 und 10 durchgeführten histopathologischen Untersuchungen.…”