Detection and distribution of equine herpesvirus 2 DNA in the central and peripheral nervous systems of ponies.

The distribution of equine herpesvirus 2 (EHV-2) DNA within neurological and lymphoid tissues from 12 EHV-2 seropositive Welsh mountain ponies was determined by PCR. The lymphoid sites sampled in this study were almost universally PCR positive, thus confirming the existing virus co-cultivation data which suggest that the lymph nodes draining the respiratory tract are the main reservoirs of EHV-2 DNA. In addition, EHV-2 DNA was also detected, albeit with lower frequency, within both the peripheral and central nervous systems (PNS and CNS) of these animals. Of the CNS sites sampled 11% were PCR-positive and in the PNS the trigeminal ganglion proved PCR-positive in 50% of the animals tested. Since the nasal epithelium is innervated by the maxillary division of the trigeminal nerve, these observations suggest that the trigeminal ganglion may represent a biologically important site for EHV-2 latency.