Replication of equid herpesvirus-1 (EHV-1) in the testes and epididymides of ponies and venereal shedding of infectious virus.

Six Welsh Mountain pony colts were infected intranasally with the Ab4 isolate of EHV-1. Clinical and virological monitoring demonstrated mild upper respiratory tract disease, with nasal shedding of virus and establishment of a cell-associated viraemia. Detailed pathological examination of the urogenital tract was performed post mortem on days 4-9 post-infection (PI). EHV-1 was isolated from the epididymis on day 8 and the testis on day 9 PI, with viral replication in endothelial cells of these organs and an associated necrotizing vasculitis and thrombosis. Productive viral infection of germinal epithelium was not observed. In a further study, three Welsh Mountain pony stallions were infected intranasally with Ab4, which again resulted in mild upper respiratory tract disease and the establishment of a cell-associated viraemia. Semen samples were collected up to day 60 PI. Two stallions showed a decrease in the proportion of morphologically normal sperm. Significant numbers of inflammatory cells were observed in the sperm-rich fraction of ejaculates collected from one stallion between days 16 and 28 PI; infectious virus was recovered from the semen of this animal between days 17 and 25 PI, after the cessation of viraemia. The affected stallion appeared clinically normal over the period of venereal EHV-1 shedding.