Viremia and nasal shedding for the diagnosis of equine herpesvirus-1 infection in domesticated horses.
Authors: Pusterla Nicola, Dorman David C, Burgess Brandy A, Goehring Lutz, Gross Margaret, Osterrieder Klaus, Soboll Hussey Gisela, Lunn David P
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: EHV-1 Detection in Blood versus Nasal Secretions Equine herpesvirus-1 causes significant disease ranging from upper respiratory infection to equine herpesvirus myeloencephalopathy (EHM), abortion, and neonatal mortality, yet optimal diagnostic sampling strategies remain incompletely defined. This systematic review synthesised 60 experimental and 20 observational studies to determine whether nasal secretions or blood samples provide superior sensitivity for EHV-1 detection via PCR, and to establish the typical window of viral shedding following infection. Nasal secretions demonstrated substantially higher detection rates in naturally infected horses presenting with respiratory disease (15% versus 9% in blood) and particularly in suspected EHM cases (94% versus 70%), though under controlled experimental conditions with serial sampling, both sample types achieved comparable sensitivity. Viral shedding typically appears within 2 days of inoculation, persists for 3–7 days in nasal secretions, whilst viraemia develops 1–2 days after nasal detection and lasts 2–7 days; critically, both may remain detectable for several weeks in some individuals. For practitioners, this underscores the importance of nasal swabs as the preferred first-line diagnostic sample in field situations—particularly given the briefer detection window—whilst recognising that single blood samples may miss active infection; serial sampling strategies and consideration of timing relative to clinical signs remain essential for reliable EHV-1 diagnosis.
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Practical Takeaways
- •For diagnosing EHV-1 in clinical settings, prioritize nasal swabs over blood samples, particularly in horses with suspected EHM where nasal detection rates are substantially higher (94% vs 70%)
- •If sampling a single time point, nasal secretions are more likely to yield a positive result than blood in naturally infected horses with respiratory disease
- •Sample horses early after suspected exposure, as nasal shedding appears within 2 days and remains detectable for only 3-7 days; viremia detection is delayed by at least 1 day
Key Findings
- •In naturally infected horses with respiratory signs, nasal shedding detection by qPCR was 15% versus 9% in blood; in suspected EHM cases, nasal detection was 94% versus 70% in blood
- •EHV-1 was typically detected in nasal secretions within 2 days of inoculation with a detection period of 3-7 days, while viremia lasted 2-7 days
- •Viremia was usually detected ≥1 day after positive identification of EHV-1 in nasal secretions
- •Under experimental conditions with multiple consecutive daily samples, blood and nasal secretions showed similar sensitivity, but in observational studies nasal secretions were consistently more successful for EHV-1 detection