Comparative Study of the Pathogenesis of Rhinopneumonitis Induced by Intranasal Inoculation of Hamsters with Equine Herpesvirus-9, Equine Herpesvirus-1 strain Ab4p and Zebra-borne Equine Herpesvirus-1.

The research study compared the severity and progress of respiratory disease in hamsters exposed to three different strains of Equine Herpesvirus (EHV): EHV-9, EHV-1 strain Ab4p, and zebra-borne EHV-1. The study found that EHV-9 caused more severe and rapid onset of symptoms, and EHV-1 strain Ab4p caused more severe upper respiratory tract disease.

Overview of the Research

• The study compared the effects of three strains of Equine Herpesvirus: EHV-9, EHV-1 strain Ab4p and zebra-borne EHV-1. These viruses are part of the Herpesviridae family and are known to cause encephalitis and rhinopneumonitis in different animal species.
• The research was conducted using hamsters as test subjects, which were divided into groups and administered varying strains of the virus.

Methodology and Findings

• Intranasal inoculation was used to infect hamsters with the respective viruses. The study tracked the development of symptoms and the progression of the disease in these hamsters.
• It was observed that hamsters infected with the EHV-9 strain showed an earlier onset of severe neurological and respiratory symptoms compared to the other two strains.
• The study also found heightened expression of the ORF 30 gene, which encodes DNA polymerase, in the lung tissue of EHV-9 infected hamsters at 4-5 days post infection. This gene expression was much higher in EHV-9 infected hamsters compared to those infected with EHV-1 Ab4p or zebra-borne EHV-1.
• All infected hamsters displayed symptoms of rhinitis, with varying severity depending on the strain of the virus. EHV-1 strain AB4p caused severe symptoms, EHV-9 induced mild symptoms, while zebra-borne EHV-1 triggered very mild symptoms.
• Viral antigens were found in the olfactory receptor neurons, inflammatory cells and desquamated epithelial cells in all virus-infected animals till five days post infection (dpi).
• A presence of tracheitis was also observed in all groups of infected hamsters, with detection of viral antigens in tracheal epithelium. Over the course of the experiment, infected hamsters developed interstitial pneumonia, bronchopneumonia and vasculitis of increasing severity.

Conclusions of the Research

• The study confirmed that both EHV-9 and zebra-borne EHV-1 strains are pneumotropic, meaning they have a tropism or preferential infection for lung tissue, in addition to showing neural tropism.
• Among the three strains, EHV-1 Ab4p was found to cause severe upper respiratory tract disease, however, no significant differences were observed in the severity of pneumonia caused by each virus strains.