Fatal equine meningoencephalitis in the United Kingdom caused by the panagrolaimid nematode Halicephalobus gingivalis: Case report and review of the literature

• Published in: Equine veterinary journal 2011-11, Vol.43 (6), p.759-763
• Main Authors: Hermosilla, C, Coumbe, K.M, Habershon-Butcher, J, Schoniger, S
• Format: Article
• Language: English
• Subjects: adults; Animals; ataxia (disorder); brain stem; case studies; cerebellum; clinical examination; eggs; eosinophilic meningoencephalitis; euthanasia; Fatal Outcome; free-living nematodes; geldings; Halicephalobus gingivalis; horse; Horse Diseases - epidemiology; Horse Diseases - parasitology; Horses; larvae; Male; Medical research; meningoencephalitis; Meningoencephalitis - epidemiology; Meningoencephalitis - parasitology; Meningoencephalitis - veterinary; Nematoda - classification; Nematode Infections - parasitology; Nematode Infections - pathology; Nematode Infections - veterinary; Nematodes; nerve tissue; panagrolaimid nematode; parasites; spinal cord; taxonomy; Tylenchida; United Kingdom - epidemiology
• ISSN: 0425-1644; 2042-3306
• DOI: 10.1111/j.2042-3306.2010.00332.x

A fatal case of eosinophilic and granulomatous meningoencephalitis caused by the free-living panagrolaimid nematode Halicephalobus gingivalis is reported in a 10-year-old Welsh gelding in the United Kingdom. Clinical examination first revealed behavioural abnormalities which rapidly progressed to severe ataxia, reduced mentation status and cranial nerve signs. Despite symptomatic treatment no amelioration of neurological signs was achieved and the horse was subjected to euthanasia. A complete post mortem examination revealed eosinophilic and granulomatous meningoencephalitis mainly affecting the cerebellum and brain stem with intralesional adult nematodes, larvae and eggs. There was also eosinophilic meningitis of the cervical spinal cord. The intralesional nematodes were morphologically consistent with the panagrolaimid nematode H. gingivalis. Although infection by this facultative neurotropic parasite is extremely rare, it needs to be considered in the differential diagnosis of central nervous signs in horses and, in particular, other equine helminthic infection of the central nervous system. This fatal case is unusual since lesions were locally very extensive and the nematodes did not colonise haematogenously to other organs as seen often in equine halicephalobosis. As the taxonomy of H. gingivalis has changed and some recent reports in the literature still refer to this species as Micronema deletrix or Halicephalobus deletrix, we here provide a short update of the species and some insights on the order Tylenchida, which contains free-living nematodes with parasitic tendencies.