The aim of the present study was to evaluate the histopathological pathogenicity associated with experimental infection of young hamsters by various strains of Equine Herpesvirus 1 (EHV-1), they are, RacL11, Kentucky D and Ab4p strains. A total of 32 specific pathogen-free male Syrian hamsters (3-week-old) were divided into 4 groups of 8 hamsters and challenged with intranasal doses of 103 pfu in 50 µl of Eagle’s minimum essential medium (MEM) per animal of each strain with a control group inoculated with MEM. All hamsters inoculated of all groups were died on day 4 and day 5 post-infection without showing any clinical signs except those inoculated with Ab4p showed neurologic signs. Microscopically; all animal groups showed encephalitis and interstitial pneumonia with more advanced changes in the Ab4p group. Both KyD and RacL11 groups showed features of hepatitis and starry sky appearance in the spleen. Only, KyD group showed multiple focal calcified areas and lymphoid follicle depletion in their kidneys and spleens, respectively. The present data provide novel findings about the comparative histopathological features of the infection of various strains of EHV-1 and also concluded that the pathogenesis among studied strains was completely different; therefore, the pathogenicity determinants need to be investigated.

Keywords: EHV-1; strains; Hamsters; Comparative Histopathology; Experimental infection