Virological and molecular biological investigations into equine herpes virus type 2 (EHV-2) experimental infections.

This research article focuses on the findings from the investigation into the pathogenicity of equine herpes virus type 2 (EHV-2), performed using two young naturally-reared ponies.

Methodology and Experimental Setup

• The researchers conducted the experiment using two 18-month-old naturally-reared ponies.
• These animals were treated with dexamethasone, a type of steroid medication often used to prepare organisms for infection procedures and reduce inflammation.
• After the treatment, one pony was intranasally inoculated with the T16 strain of EHV-2, which was originally isolated from a foal suffering from keratoconjunctivitis superficialis. The other pony received the LK4 strain, derived from a horse with upper respiratory tract disease.

Results and Observations

• While no instances of fever were detected in either of the ponies, they both developed symptoms like conjunctivitis, lymphadenopathy, and coughing, indicating an established EHV-2 infection.
• Traces of EHV-2 were detected in nasal mucus samples up until the 12th day post infection (p.i.), in eye swabs until the 10th day p.i., and consistently throughout the investigation in the buffy coat cells of both ponies.
• Significant increase in EHV-2-specific antibody titres were seen 18 days post infection, indicative of an immune response being mounted by the infected ponies.
• Post dexamethasone injections 3 months p.i., the presence of the viral infectious agent was once again detected in nasal mucus and conjunctival swabs from both the ponies for about a week.

Post Mortem Findings

• After the demise of the animals, a study of the distribution of EHV-2 genome across different tissues was initiated using a method called nested PCR.
• Presence of EHV-2 was discovered in lymphoid tissues, lung, conjunctiva, trigeminal ganglia, and the olfactory lobes of the pony that was given the LK4 strain.
• In contrast, for the pony inoculated with the T16 strain, only the left eye’s conjunctiva was PCR positive, implying a presence of EHV-2.