Variation in cellular tropism between isolates of equine herpesvirus-1 in foals

Subtype-1 isolates of Equine herpesvirus-1 (EHV-1) from a quadriplegic horse and from an aborted foetus were compared with each other and with a subtype-2 respiratory isolate. All 3 isolates were detected in the epithelium and macrophages of the respiratory tract. Both the paresis and foetal subtype-1 isolates replicated in the epithelium of the ileum and this correlated with the recovery of virus from faeces in vivo. The paresis subtype-1 isolate also had a predelection for vascular endothelial cells, particularly in the nasal mucosa, but also in the lungs, central nervous system, adrenal and thyroid. In the 9 foals inoculated with the paresis isolate two developed hind limb dysfunction, four developed diarrhoea, and one of these 4 died with an intussusception. The differences between these isolates are discussed in relation to other herpesviruses.