Experimental infection with neuropathogenic equid herpesvirus type 1 (EHV-1) in adult horses.

The research article discusses an experiment conducted to investigate three hypotheses regarding the impact of a neuropathogenic strain of Equid Herpesvirus Type 1 (EHV-1) on adult horses. The main findings show that a large dosed inhalation does not ensure viraemia – a condition where the virus enters the bloodstream and hence spreads – in all horses, though viraemia likely prerequisites for developing myeloencephalopathy (brain and spinal cord disease). Also, the cerebrospinal fluid (CSF) composition could predict histopathological changes confirming myeloencephalopathy.

Experiment Methodology

• The researchers conducted an experimental infection with a neuropathogenic strain of Equid Herpesvirus Type 1 (EHV-1) on four EHV-1 seronegative horses.
• The horses were inoculated with the EHV-1 virus through inhalation.

Hypotheses Tested

• The large inhaled dose of the neuropathogenic EHV-1 strain was hypothesized to induce a cell-associated viraemia in all infected horses.
• It was postulated that neurological disease would only occur in viraemic horses.
• The researchers also hypothesized that the composition of the cerebrospinal fluid (CSF) following EHV-1 viraemia would provide an indication for the development of Equid Herpesvirus myeloencephalopathy (EHM).

Key Findings

• Three out of the four horses developed signs of neurological disease after being inoculated with the virus.
• However, clinical symptoms varied in severity among the horses and were mild in two of them. The two horses with mild symptoms did not present typical EHM histopathological findings.
• The horse with moderate symptoms was the only one found to be viraemic and presented with xanthochromic CSF and spinal cord histopathology findings characteristic of EHM.
• The cell-associated viraemia was not guaranteed, despite a large-dose inoculation with EHV-1, showing that the relationship between dosage and viraemia is not necessarily direct.
• Viraemia was probably a pre-requisite for subsequent development of EHM, indicating a potential correlation between the incidence of viraemia and the occurrence of EHM.
• The study also suggested that the changes used to confirm EHM could be predicted from CSF analysis, which could be used as a potential diagnostic tool for early detection of EHM.