Neurological disease associated with EHV-1-infection in a riding school: clinical and virological characteristics.
Authors: van Maanen C, Sloet van Oldruitenborgh-Oosterbaan M M, Damen E A, Derksen A G
Journal: Equine veterinary journal
Summary
# Editorial Summary: EHV-1 Neurological Disease Outbreak in a Riding School A 1995 outbreak of neurological equine herpesvirus type 1 (EHV-1) affecting 41 horses in a well-managed riding school provided critical insights into the disease's clinical progression, diagnosis, and long-term prognosis. Of the 20 horses showing neurological signs, 10 required intensive care with slings for 2–18 days and bladder catheterisation for 2–16 days; postmortem examination confirmed vasculitis with perivascular mononuclear infiltration and axonal degeneration of the central nervous system. Virological and serological confirmation was achieved through isolation of EHV-1 from nasal swabs and identification of the genome type as EHV-1.IP using restriction enzyme analysis and monoclonal antibodies; serological testing revealed 28 horses seroconverted during the outbreak whilst 12 showed pre-existing high titres, with EHV-1-specific glycoprotein G ELISA proving particularly valuable for diagnosis. Whilst horses with mild neurological signs recovered completely within one year, the prognosis for recumbent horses was substantially poorer: of eight horses surviving intensive care, only three returned to former performance levels, and all five that became pasture-sound required euthanasia within four years due to persistent ataxia and incontinence. For practitioners, this outbreak underscores the grave long-term consequences of severe EHV-1 neuropathy despite short-term survival, emphasises the importance of strategic sampling and serology in febrile in-contact horses for diagnosis, and highlights the critical need for biosecurity protocols when introducing new horses into established populations.
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Practical Takeaways
- •EHV-1 neurological disease carries a grave prognosis for recumbent horses; even horses that survive intensive care often develop permanent neurological deficits requiring long-term euthanasia decisions
- •Introduction of a single purchased horse can trigger rapid spread of neurological EHV-1 through a closed population within 3 weeks; vigilant quarantine protocols are critical for riding school biosecurity
- •Diagnosis requires strategic sampling of febrile in-contact horses with both virological (nasal swabs for isolation) and serological testing; gG-specific ELISA is more reliable than older serological methods for confirming EHV-1 involvement
Key Findings
- •Of 41 horses in the outbreak, 20 showed neurological signs with 10 requiring intensive care and slings; 8 of those survived but only 3 returned to former performance level
- •All 5 horses that were pasture-sound at 1-year follow-up required euthanasia by 4-year follow-up due to persistent mild ataxia and incontinence
- •EHV-1.IP genome type was identified and strains were identical to an epidemiologically unrelated outbreak 2 months earlier, suggesting common viral circulation
- •Serological testing (CF, SN, gG-specific ELISA) combined with viral isolation from nasal swabs of febrile in-contact horses is essential for diagnosis of EHV-1 neurological disease