Equis ISSN 2398-2977

CNS: verminous encephalomyelitis

Synonym(s): Neural angiostrongylosis

Contributor(s): Frank Andrews, Ruth Morgan, Vetstream Ltd

Introduction

  • Cause: inflammation associated parasitic migration through the central nervous system.
  • Signs: variable - multifocal neurological disease; hindquarter ataxia progressing to recumbency.
  • Diagnosis: CSF analysis; post-mortem histopathology.

Pathogenesis

Etiology

  • Aberrant parasite migration:
    • Strongylus vulgaris  Strongylus spp  .
    • Strongylus equinus.
    • Draschia megastoma.
  • Neurotropic nematodiasis:
    • Angiostrongylus cantonensis: lung parasite of the rat (particularlyRattus norvegicus); migration in the CNS of non-permissive host, eg primates, dogs, horses, wallabies.
    • Halicephalobus gingivalis (deletrix).
    • Setariaspp.

Predisposing factors

General
  • Irregular or absent parasite control program.
  • Grazing at pasture with adult animals.
  • Contact with deer.

Pathophysiology

  • Mechanical damage to CNS due to migration of parasites.
  • Granulomatous or eosinophilic inflammatory response to parasite migration.
  • Aberrant or neurotropic migration of parasite larvae   →   mechanical damage to CNS in brainstem, cerebellum and spinal cord +/- granulomatous inflammatory response   →   multiple foci of malacic lesions.

Timecourse

  • 7-14 days.

Epidemiology

  • SeeStrongylespp.
  • A. cantonensis:
    • Nematode normally migrates through the CNS of the rat as third and fourth stage larvae.
    • Young adults leave the CNS and lodge in the pulmonary artery and the right ventricle of the heart.
    • Eggs are circulated to the alveolar capillaries.
    • First stage larvae enter the alveoli and migrate up the trachea to be swallowed and passed in the feces of the rat.
    • First stage larvae infect an intermediate host (mollusc - terrestrial and aquatic snails and slugs).
    • Mammalian hosts are infected by ingestion of intermediate or paratenic hosts.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lacombe V A (2013)Challenges associated with the diagnosis and treatment of parasitic encephalitis.Equine Vet Educ25(12), 605-606 VetMedResource.
  • Wilford S, Weller R & Dunkel B (2013)Successful treatment of a horse with presumed parasitic encephalitis.Equine Vet Educ25(12), 601-604 VetMedResource.
  • Hahn C (2006)The wobbly horse: differential diagnoses.In Pract28(1), 8-13 VetMedResource.
  • Costa L R Ret al(2000)Verminous meningoencephalomyelitis by Angiostrongylus (= Parastrongylus) cantonensis in an American Miniature horse.Equine Vet Educ12(1), 2-6 VetMedResource.
  • Anderson R C, Linder K E & Peregrine A S (1998)Halicepahlobus gingivalis (Stefanski, 1954) from a fatal infection in a horse in Ontario, Canada with comments on the validity of H. deletrix and a review of the genus.Parasite5(3), 255-261 PubMed.
  • Tiefke J P, Schmidt E, Traenckner C M & Bauer C (1998)Halicephalobus (Syn. Micronema) deletrix as a cause of granulomatous gingivitis and osteomyelitis in a horse.Tierarztl Prax Ausg G Grosstiere Nutztiere26(3), 157-161 PubMed.
  • Wright J Det al(1991)Equine neural angiostrongylosis.Aust Vet J68, 58-60 PubMed.


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