Pharmacologic interventions for the treatment of equine herpesvirus-1 in domesticated horses: A systematic review.
Authors: Goehring Lutz, Dorman David C, Osterrieder Klaus, Burgess Brandy A, Dougherty Kelsie, Gross Peggy, Neinast Claire, Pusterla Nicola, Soboll-Hussey Gisela, Lunn David P
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Pharmacologic Treatment of Equine Herpesvirus-1 Despite EHV-1's significant clinical impact—causing respiratory disease, neurological complications, abortion, and neonatal mortality—evidence supporting pharmacological interventions remains sparse and unconvincing. A comprehensive systematic review of six major medical databases identified only 9 peer-reviewed studies from over 7,000 candidate publications investigating therapeutic agents (including valacyclovir, interferon, immunomodulators, and herbal supplements) for EHV-1 prevention or treatment in horses. Study quality was considerably limited by small sample sizes, moderate-to-high bias risk, and predominantly negative or minimally efficacious results across all tested interventions. Given this lack of robust evidence, practitioners cannot reliably depend on pharmacological approaches to reduce either disease incidence or severity in EHV-1-infected horses, highlighting an urgent need for well-designed clinical trials and alternative management strategies such as enhanced biosecurity, vaccination protocols, and supportive care. The authors' findings underscore a critical gap in equine medicine and suggest future research should prioritise rigorous investigation of novel antivirals and immunotherapeutic approaches to better address this economically and welfare-significant viral disease.
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Practical Takeaways
- •Currently available pharmacologic treatments show minimal evidence of benefit for preventing or reducing EHV-1 disease severity in horses; focus should remain on biosecurity and supportive care
- •Veterinarians should counsel horse owners that no pharmacologic therapy has demonstrated clear clinical efficacy for EHV-1, and discuss evidence-based management strategies instead
- •The lack of effective pharmacologic interventions highlights the importance of vaccination programs and infection control measures as primary prevention strategies
Key Findings
- •Of 7009 identified studies, only 9 met inclusion criteria for in vivo therapeutic interventions in horses with EHV-1
- •Interventions tested included valacyclovir, small interfering RNAs, Parapoxvirus ovis-based immunomodulator, human alpha interferon, herbal supplement, cytosine analog, and heparin
- •Most studies reported no benefit or minimal efficacy for any tested intervention in preventing or treating EHV-1-associated disease
- •Risk of bias was moderate to high across included studies with small sample sizes and evidence ranging from randomized controlled trials to observational trials