Efficacy of a live equine herpesvirus-1 (EHV-1) strain C147 vaccine in foals with maternally-derived antibody: protection against EHV-1 infection.
Authors: Patel J R, Didlick S, Bateman H
Journal: Equine veterinary journal
Summary
# Editorial Summary: EHV-1 Vaccination in Young Foals Maternally-derived antibodies have historically prevented effective vaccination against equine herpesvirus-1 in foals under five to six months of age, leaving this age group—a critical transmission reservoir—vulnerable to febrile respiratory disease. Patel and colleagues evaluated whether a live attenuated EHV-1 strain (C147) could overcome this immunological interference by vaccinating foals aged 1.4–3.5 months intranasally, then performing controlled viral challenge to assess protection. Despite the presence of circulating virus-neutralising maternal antibodies, vaccinated foals demonstrated significant partial protection characterised by reduced fever, decreased nasal shedding, and lower leucocyte-associated viraemia compared to unvaccinated controls following challenge. This finding has substantial implications for disease control strategies, as vaccinating young foals could meaningfully reduce EHV-1 transmission within susceptible populations before maternal immunity wanes. For practitioners advising on foal health protocols, these results suggest that earlier intervention against EHV-1 may be feasible, potentially shifting current preventive medicine approaches in facilities where herpesvirus poses significant management or economic concerns.
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Practical Takeaways
- •This vaccine offers a new immunization option for foals under 6 months old, addressing a significant gap in current EHV-1 prevention strategies for an important disease reservoir population
- •Practitioners can now consider vaccinating young unweaned foals against EHV-1 respiratory disease rather than waiting until 5-6 months of age
- •Early vaccination of foals may help reduce EHV-1 transmission and disease incidence in breeding operations and mixed-age horse populations
Key Findings
- •A single intranasal dose of live EHV-1 strain C147 vaccine provided partial but significant protection against febrile respiratory disease in foals aged 1.4-3.5 months despite presence of maternally-derived antibodies
- •Vaccinated foals showed reduced virus shedding in nasal mucus and decreased viraemia following EHV-1 challenge
- •The vaccine demonstrated efficacy in breaking through maternal antibody interference, enabling immune response in young unweaned foals