J Vet Sci.  2017 Dec;18(4):551-554. 10.4142/jvs.2017.18.4.551.

Eosinophilic encephalomyelitis in horses caused by protostrongylid parasites

• Bak EJ
• Jean YH
• Woo GH

• KMID: 2398516
• DOI: http://doi.org/10.4142/jvs.2017.18.4.551

Abstract

Four thoroughbred horses showing lameness, ataxia, circling, depression, recumbency, and seizures, were examined. The horses had gross, pale- to dark-red manifestations and foci in the central nervous system (CNS). Multifocal to coalescing eosinophilic necrotizing encephalomyelitis was observed histologically in the CNS along with intact or degenerated nematodes. Nematodes had polymyarian-coelomyarian musculature, a smooth thin cuticle, and intestines lined by multinucleated cells with microvilli. These traits suggested the nematodes belonged to the family Protostrongylidae, which includes Parelaphostrongylus tenuis. It was concluded that the horses were infected by nematodes, presumably Parelaphostrongylus tenuis, resulting in eosinophilic necrotizing encephalomyelitis.

Keyword

Parelaphostrongylus tenuis; central nervous system; encephalomyelitis; horses; nematode

MeSH Terms

Ataxia
Central Nervous System
Depression
Encephalomyelitis*
Eosinophils*
Horses*
Humans
Intestines
Microvilli
Parasites*
Seizures

Figure

• 

  Fig. 1 Gross findings and histopathological findings of brain in affected horses. (A) Cut surface of the brain (horse No. 3). Note the large dark-red area in the midbrain and pons (arrow). (A inset) Wet greasy areas (short arrows) and pale-red foci (long arrows) were scattered throughout the white matter. The boundary between grey matter and white matter was not demarcated (arrowheads). (B) Cerebrum (horse No. 3). Marked eosinophilic lymphohistiocytic inflammation and malacia with vacuolation and hemorrhage were observed in white matter. (B inset) The roundworms had polymyarian-coelomyarian musculature (arrows), a smooth thin cuticle, and intestines lined by multinucleated cells with microvilli (arrowheads). (C) Spinal cord (horse No. 2). Severe eosinophilic granulomatous myelitis and intralesional roundworm infective third-stage larvae were observed in white matter. Axonal spheroids, hemorrhage, and malacia were also present. (D) Cerebrum (horse No. 1). The migration tracts of parasites appear as chronic lesions. Migration tracts were mainly observed in white matter or in the border between white matter and grey matter. H&E stain (B–D and B inset), Scale bar = 500 µm (B and D), 200 µm (B inset and C).

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