Recent advancements in our understanding of equid gammaherpesvirus infections.
Authors: Easton-Jones Charlotte
Journal: Equine veterinary journal
Summary
Equid gammaherpesviruses are nearly ubiquitous in horse populations, yet their precise role in immune dysregulation and disease pathogenesis remains poorly understood, with genetic variability and multi-strain infections potentially holding clinical significance. Easton-Jones's 2022 review synthesises current knowledge on infection dynamics, revealing that initial exposure typically occurs peripartum in foals, after which the virus establishes latency within peripheral blood mononuclear cells—though emerging evidence suggests EHV-5 may gain direct lymphocyte access via tonsillar crypts following respiratory exposure. Whilst EHV-5 has a well-established link to equine multinodular pulmonary fibrosis, evidence for its involvement in milder respiratory conditions and performance problems remains limited, contrasting sharply with EHV-2's recognised association with these presentations. Transport-related stress has been identified as a significant trigger for viral reactivation and shedding in latently infected adults, with transmission occurring primarily through the upper respiratory tract. Critically, the current evidence base provides minimal support for antiviral efficacy in treating gammaherpesvirus infections, highlighting a substantial gap between clinical suspicion and proven interventions that should inform both diagnostic interpretation and treatment recommendations in practice.
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Practical Takeaways
- •Recognize that gammaherpesvirus infection is nearly universal in equine populations and monitor for clinical signs, particularly respiratory disease and performance issues, especially in recently transported horses.
- •Be aware that stress from transport can trigger viral reactivation and shedding; implement stress-reduction strategies during and after transport when possible.
- •Understand that antiviral treatments lack proven efficacy for these infections, so focus on supportive care, stress management, and general immune support rather than expecting pharmaceutical solutions.
Key Findings
- •Equid gammaherpesviruses establish latency in peripheral blood mononuclear cells following peripartum infection in foals, with potential direct access via tonsillar crypts.
- •EHV-5 is associated with equine multinodular pulmonary fibrosis but lacks evidence for involvement in milder respiratory disease unlike EHV-2.
- •Transport stress is identified as a risk factor for reactivation and shedding of latent equid gammaherpesviruses in adult horses.
- •Current evidence does not support the effectiveness of antiviral drugs for treating equine gammaherpesvirus infections.