The pathogenicity in mice of respiratory, abortion and paresis isolates of equine herpesvirus-1.

The study explores the pathogenicity of various isolates of equine herpesvirus-1 on mice, emphasizing on isolates linked with paralysis, abortion, or respiratory illnesses in horses. It reveals the varying pathogenic behavior and distribution of different isolates in mouse brains and further infections following exposure.

Research Objective and Methodology

• The objective of this research was to examine the ability of eleven different isolates of equine herpesvirus-1, primarily linked with paralysis, abortion, and respiratory diseases in horses, to infect the brains of mice.
• 2-day old mice were intracerebral inoculated, meaning the virus was directly injected into the brains of the mice, to establish the infections.
• The isolated viruses were all subtype 1, with some originating from the UK cases of horses affected by the said disorders, while others were from established strains.

Findings and Results

• The research identified two subgroups amongst the eleven virus isolates based on their pathogenic behavior.
• The first, less pathogenic subgroup, included five isolates, which customarily localized to the olfactory areas of the mice brains, indicating a lower intensity infection.
• The second, more pathogenic subgroup, comprised of six isolates, three of which were known to be responsible for causing equine paralysis. These showed a more extensive distribution in the mice’s brains, indicating higher pathogenicity. They were also found to cause viraemia, a condition where the virus is present in the bloodstream, allowing it to spread to various parts of the body. The infection spread from neurons to the bronchial and renal epithelium and lymphoid cells in the spleen.
• The study also included five respiratory isolates of subtype-2 of the virus. However, no isolation was made from the administered mice, suggesting these types either failed to infect or were swiftly cleared from the system.

Significance of the Study

• The research offers valuable insights into the pathogenicity and behavior of different equine herpesvirus-1 subtypes, especially when they relate to specific disease manifestations in the horse population.
• Understanding the way these viruses behave in a model organism like mice can be instrumental in understanding their infection mode, pathogenicity, and possible countermeasures in the primary hosts, which, in this case, are horses.