Serological responses of mares and weanlings following vaccination with an inactivated whole virus equine herpesvirus 1 and equine herpesvirus 4 vaccine.

The research explores the immune response of horses and foals to a vaccination for Equine Herpesvirus 1 and 4 (EHV-1/4), a major disease that causes respiratory issues and abortion. The study indicates that knowing the antibody status could help establish a more targeted vaccination strategy, potentially leading to significant cost savings for the industry.

Study Setup

• The study examines EHV-1, a worldwide issue causing respiratory disease and abortion in horses.
• A total of 159 mares (female adults) and 101 foals (young horses) on a large stud farm were used for the study.
• The subjects were vaccinated with an inactivated whole virus EHV-1/4 vaccine according to the manufacturer’s guidelines.
• Two types of tests, EHV glycoprotein D (gD)-specific ELISA and a type-specific glycoprotein G (gG) ELISA, were performed to check the subjects’ responses to the vaccine.

Results of the Vaccination

• Using the gD ELISA, 13.8% of mares and 42.6% of foals displayed a response to the vaccination. With the gG ELISA, the response rates were 28.9% of mares and 46.6% of foals.
• Responder mares and foals had lower initial ELISA absorbances than non-responders which suggests that they had less exposure to the herpes virus before vaccination.
• Mares who responded to the vaccine were ten times more likely to give birth to responding foals, while non-responding mares were six times more likely to have non-responder foals.
• Mares aged 7 years or less and foals aged 4 months or more were more likely to respond to vaccination than other age groups.

Implications of the Study

• The study found no relation between the mare’s response and the number of previous vaccinations received.
• Those classed as “persistently seropositive” mares did not respond to the vaccine, indicating possible resistance.
• These findings highlight that knowing the antibody status could aid in a more refined vaccination strategy, potentially reducing costs for the industry.
• For example, persistently seropositive mares who are not likely to benefit could avoid unnecessary vaccination, and foals of responder mares could be vaccinated sooner to increase their chances of a response.