Serological and virological investigations of an equid herpesvirus 1 (EHV-1) abortion storm on a stud farm in 1985.

This research presents findings from a closely studied outbreak of Equid herpesvirus 1 (EHV-1) on a stud farm in England in 1985. The objective was to investigate patterns in the virus’ spread and its relation to abortive outcomes in the infected mares.

Research Context

• The research was conducted during an extensive outbreak of EHV-1, a type of herpesvirus specifically affecting equids, that resulted in a surge of abortions among pregnant mares on a stud farm in England in 1985.
• The outbreak provided a large enough sample size of 67 mares to conduct a comprehensive study on the virus’ behavior and its relation to the mare’s pregnancy.

Methodology and Key Findings

• Out of the 67 mares, 31 were infected with EHV-1. This led to the loss of 22 fetuses or foals, indicating the severity of the virus.
• The researchers found that the spread of the virus was closely tied to the movement of the mares. This suggests that the mares, even if showing no outward signs of illness during the infection’s incubation period, were key contributors to the spread of the virus.
• The timing of infection varied among the mares, occurring between 1 to 4 months before the expected foaling date.
• They also determined that there was no relationship between the gestational age at the time of the virus’ introduction and the resulting abortion. This means that whether a mare was infected early or later in pregnancy, there was no significant effect on the outcome of aborting.
• The time period between the estimated infection date and the resulting abortion varied greatly, with ranges between 9 days to 4 months.
• The virus was found in the nasopharynx (part of the throat) of three foals born during the outbreak who appeared healthy, indicating asymptomatic carriers as a possible vector for the virus’ spread.

Significance of the Research

• This research provides valuable insights into the behavior of EHV-1 in equid populations, particularly the potential for asymptomatic carriers to spread the virus.
• The findings highlight the importance of strict movement controls among equid populations particularly during outbreak situations and the necessity of closely monitoring the health status of all horses, not just visibly ill ones.
• The study further sheds light on the potential for EHV-1 to cause severe reproductive losses in equid populations, providing useful information to guide prevention and control measures.