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

This study investigates the replication of Equid Herpesvirus-1 (EHV-1) in the reproductive organs of ponies and how it is transmitted sexually. In a series of experiments, researchers infected ponies with EHV-1 and analyzed its effects on the health of the animals, its presence within their reproductive organs, and its presence in their semen.

Introduction and Methodology

• The research focused on the Equid Herpesvirus-1 (EHV-1), a type that affects horses and ponies, causing respiratory disease and, in some severe cases, neurological disorders.
• Six Welsh Mountain pony colts were intranasally infected with the EHV-1 virus — also known as Ab4 isolate — to induce mild upper respiratory tract disease.
• The colts were monitored both clinically and virologically, which included observing nasal shedding of the virus and the establishment of a viraemia (the presence of viruses in the blood).
• Post-death inspections were conducted between the 4th and 9th days after infection to study the detailed pathological effects on the pony’s urogenital tract.

First Phase of Findings

• On the 8th and 9th day post-infection (PI), EHV-1 was isolated from the epididymis and testes respectively.
• Viral replication was observed in the endothelial cells of these organs, leading to necrotizing vasculitis (inflammation and damage of blood vessels) and thrombosis (formation of a blood clot).
• However, productive viral infection in the germinal epithelium (the tissue from which sperm cells arise) was not observed

Second Phase of Study and Findings

• In a further study, three Welsh Mountain pony stallions were similarly infected with Ab4.
• Samples of semen were collected for up to 60 days post-infection.
• Two of the stallions showed a decrease in morphologically normal sperms, indicating a potential affect of the virus on sperm quality.
• Significant numbers of inflammatory cells were observed in the sperm-rich fraction of ejaculates collected from one stallion between days 16 and 28 post-infection.
• Infectious virus was found in the semen of this stallion during days 17 to 25 post-infection, suggesting the possibility of sexually transmitting the virus, even after viraemia had ceased.
• Despite the presence of the virus in the semen, the affected stallion appeared clinically normal over the period of sexual shedding of EHV-1, indicating absence of any noticeable clinical signs.

Conclusion

• This research contributes significantly to understanding possible routes of EHV-1 transmission involving sexual activities. The study has shed light on the potential for sexual transmission of this virus, despite not having visible symptoms, a factor that could be crucial in disease control strategies for herd health management.