Study on the infectivity of equine herpesvirus 9 (EHV-9) by different routes of inoculation in hamsters.
Authors: El-Habashi N, Murakami M, El-Nahass E, Hibi D, Sakai H, Fukushi H, Sasseville V, Yanai T
Journal: Veterinary pathology
Summary
# Editorial Summary: EHV-9 Infectivity and Neurotropism via Multiple Routes Equine herpesvirus 9 (EHV-9), a neurotropic virus originally identified in gazelles, presents a novel concern for equine practitioners due to its capacity to breach the blood-brain barrier and cause severe meningoencephalitis. This experimental study evaluated how the virus establishes infection and triggers neuropathology through five different inoculation routes—intranasal, ocular, oral, intravenous, and intraperitoneal—using hamsters as a model system to understand potential pathogenic mechanisms in natural infection. Nasal inoculation proved most efficient at inducing clinical neurological signs (100% of animals), followed by oral and peritoneal routes (~25% each), whilst intravenous and ocular inoculations failed to produce observable neurological disease despite viral replication at the inoculation site. Across all successful routes except intravenous, histopathology revealed consistent lymphocytic meningoencephalitis characterised by neuronal necrosis, perivascular immune cell infiltration, and intranuclear inclusion bodies, with viral antigen localised specifically to degenerating neurons. These findings suggest EHV-9 utilises multiple neuroinvasive pathways—potentially retrograde axonal transport along peripheral nerves rather than solely through olfactory routes—to reach the central nervous system, implying that practitioners should consider this virus in differential diagnoses for unexplained neurological disease in horses and remain alert to potential transmission routes beyond typical respiratory exposure.
Read the full abstract on PubMed
Practical Takeaways
- •EHV-9 is a neurotropic virus with multiple routes of potential infection; respiratory exposure poses highest risk for rapid neurological disease onset
- •The variable clinical presentation based on exposure route suggests that clinical signs and severity of EHV-9 may depend on how horses are initially exposed to the virus
- •Understanding that virus can reach the brain via non-respiratory pathways may inform biosecurity protocols for managing infected animals and preventing nervous system involvement
Key Findings
- •Nasal inoculation of EHV-9 caused neurological signs in 100% of hamsters by day 3 post-inoculation, while oral and peritoneal routes affected ~25% of animals by days 6 and 9 respectively
- •All infected animals except those receiving intravenous inoculation developed lymphocytic meningoencephalitis with characteristic lesions including neuronal necrosis and intranuclear inclusion bodies
- •Viral antigen distribution varied by inoculation route, suggesting EHV-9 may travel to the brain via nerve pathways rather than solely through the olfactory route