Prevalence factors associated with equine herpesvirus type 1 infection in equids with upper respiratory tract infection and/or acute onset of neurological signs from 2008 to 2014.
Authors: Pusterla N, Mapes S, Akana N, Barnett C, MacKenzie C, Gaughan E, Craig B, Chappell D, Vaala W
Journal: The Veterinary record
Summary
# EHV-1 Detection in Horses with Respiratory and Neurological Disease: What the Prevalence Data Tell Us Between 2008 and 2014, researchers screened 4,228 horses presenting with fever, respiratory disease, and/or acute neurological signs for equine herpesvirus type 1 (EHV-1) using quantitative PCR of nasal secretions and blood samples, identifying the virus in 2.7% (117 cases), with the majority harbouring the non-neuropathogenic N752 genotype. Racing horses were significantly overrepresented in the EHV-1-positive cohort, suggesting either greater exposure risk through competition and transport networks or enhanced surveillance bias within that population. Counterintuitively, horses testing positive for EHV-1 reported fewer classical signs of systemic illness—depression, anorexia, nasal discharge and cough were all significantly *less* frequent in qPCR-positive cases—whereas neurological deficits were significantly *more* common, indicating that EHV-1 should be on the differential diagnosis list for cases presenting with primarily neurological rather than respiratory manifestations. For practitioners, these findings underscore that reliance on clinical presentation alone may lead to missed EHV-1 diagnoses; the atypical clinical picture (absence of respiratory signs, presence of neurological dysfunction) alongside the predominance of non-neuropathogenic strains highlights the importance of molecular confirmation rather than presumptive treatment based on symptom pattern alone.
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Practical Takeaways
- •EHV-1 should be considered in the differential diagnosis for horses presenting with acute neurological signs, particularly racing horses, even if classical respiratory signs are mild or absent
- •The dominance of non-neuropathogenic N752 genotype suggests lower neurological risk, but comprehensive diagnostics remain essential as neurological cases occurred in this cohort
- •Clinicians should perform qPCR testing on both nasal secretions and whole blood to maximize detection sensitivity in suspected EHV-1 cases
Key Findings
- •EHV-1 qPCR-positive cases represented 2.7% (117/4228) of equids tested, with most isolates being non-neuropathogenic N752 genotype
- •Racing horses were significantly over-represented among EHV-1 qPCR-positive cases
- •Neurological deficits were more frequently reported in EHV-1 qPCR-positive equids, while depression, anorexia, nasal discharge and coughing were significantly less frequent
- •Study provides contemporary prevalence data for EHV-1 detection in blood and nasal secretions from horses presenting with fever, respiratory or neurological signs