Lesions and Distribution of Viral Antigen in the Brain of Hamsters Infected With Equine Herpesvirus (EHV)-9, EHV-1 Strain Ab4p, and Zebra-Borne EHV-1.
Authors: El-Habashi Nagwan, El-Nahass El-Shaymaa, Abd-Ellatieff Hoda, Saleh Asmaa, Abas Osama, Tsuchiya Yuya, Fukushi Hideto, Yanai Tokuma
Journal: Veterinary pathology
Summary
# Editorial Summary: Neuropathological Comparison of EHV Strains in Experimental Encephalitis EHV-9 and certain strains of EHV-1 are known neurotropic pathogens, yet their mechanisms of brain invasion and the severity of resulting neuropathology remain incompletely understood. Researchers inoculated hamsters intranasally with EHV-9, EHV-1 strain Ab4p, or zebra-borne EHV-1, then performed serial neuropathological examinations and viral antigen mapping at seven timepoints over one week postinfection. EHV-9 proved substantially more virulent, causing 75% mortality and widespread neuronal necrosis, whilst both EHV-1 variants produced no deaths but generated distinct inflammatory signatures characterised by perivascular infiltration and glial proliferation; critically, the three viruses displayed markedly different patterns of cerebral lesion distribution and viral antigen localisation despite all initiating infection in the nasal mucosa. These findings suggest that although EHV variants likely reach the central nervous system via olfactory or trigeminal routes, viral strain fundamentally determines both the neuropathological phenotype and clinical severity—information with potential implications for understanding why certain EHV-1 field strains (such as the neuropathogenic variant responsible for EHV-1 myeloencephalopathy) cause severe neurological disease whilst others remain largely respiratory pathogens.
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Practical Takeaways
- •Different EHV strains cause markedly different neurological disease severity and pathology patterns—this fundamental difference has implications for understanding clinical manifestations in horses and designing strain-specific interventions
- •The olfactory/trigeminal nerve route of viral CNS entry suggests that early respiratory containment and local immune responses at the nasal mucosa may be critical intervention points
- •Laboratory findings in a hamster model provide baseline neuropathological data for comparing with equine EHV encephalitis cases, but direct clinical translation requires caution given species differences
Key Findings
- •EHV-9 induced 75% mortality in hamsters with severe neurological signs at 60-72 HPI, while EHV-1 strains (Ab4p and zebra-borne) caused 0% mortality
- •EHV-9 produced widespread neuronal necrosis, whereas EHV-1 strains showed marked perivascular inflammatory cell infiltration and gliosis
- •All three viruses induced meningoencephalitis following nasal inoculation, suggesting olfactory and/or trigeminal nerve transmission routes to the brain
- •Neuropathological lesion severity and distribution varied significantly between virus strains, indicating different CNS invasion and pathogenic mechanisms