Med. Weter. 81 (11), 598-604, 2025
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| MOHAMED S. AHMED, YASSER M. GHANEM, ABEER M. ALGHAMDI, MANAL F. EL-KHADRAGY, SAMY KASEM, AWLAD WADAIR A. SAID, AND EHAB KOTB ELMAHALLAWY |
| Comparative Descriptive Histopathological Study of Various Strains of Equine Herpesvirus Type 1 (EHV-1) Infection in Hamster Model |
| Equine Herpesvirus-1 (EHV-1) is a major cause of upper respiratory tract infections in horses, frequently associated with abortion in pregnant mares, neonatal death, and equine herpesvirus myeloencephalopathy (EHM). These clinical outcomes lead to substantial economic losses in the equine industry. Despite the recognized clinical significance of EHV-1, limited information is available regarding the comparative histopathological alterations induced by different viral strains under controlled experimental conditions. The objective of the present study was to investigate the pathogenicity of three distinct EHV-1 strains, namely RacL11, Kentucky D (KyD), and Ab4p, using a Syrian hamster model. A total of 32 specific pathogen-free male Syrian hamsters, three weeks of age, were randomly allocated into four groups (n = 8 per group). Each experimental group was intranasally inoculated with 10³ plaque-forming units (PFU) of one EHV-1 strain in 50 μL of Eagle’s minimum essential medium (MEM), while the control group received MEM alone. All hamsters infected with the KyD and RacL11 strains died on days 4 and 5 post-infection (p.i.), respectively, without exhibiting neurological symptoms. In contrast, animals infected with the Ab4p strain developed neurological signs, with four animals dying on day 5 p.i. and the remaining four on day 6 p.i. Histopathological examination revealed encephalitic changes in all infected groups, characterized by microglial cell infiltration, formation of glial nodules, and perivascular lymphocytic cuffing. The Ab4p group demonstrated the most advanced neuropathological alterations. In addition, prominent viral hepatitis was observed in both the KyD and RacL11 groups. All groups showed a similar moderate degree of interstitial pneumonia. Interestingly, the kidneys of all groups were normal, except those of the KyD group, which showed multiple focal calcified areas with dilatation of Bowman’s space and glomerular tuft shrinkage. The spleen of the KyD and RacL11 groups showed a starry-sky appearance with scattered macrophages, and only group KyD exhibited lymphoid follicle depletion. All infected groups exhibited a moderate degree of interstitial pneumonia. The kidneys appeared normal in all groups, except for the KyD group, which showed focal calcification, dilation of Bowman’s space, and glomerular tuft shrinkage. The spleens of both the KyD and RacL11 groups exhibited a starry-sky appearance due to scattered macrophages, but lymphoid follicle depletion was noted only in the KyD group. These findings provide novel and detailed insights into the strain-specific histopathological outcomes of EHV-1 infection in a non-equine experimental model. The distinct differences in neurotropism and systemic organ involvement between the strains highlight the complexity of EHV-1 pathogenesis. The data strongly suggest that virulence and tissue tropism are strain-dependent, confirming the need for further investigation into the molecular determinants responsible for pathogenic variability among EHV-1 strains. |
| Keywords: EHV-1; Hamsters; Histopathology; Experimental infection |