Passive transfer and rate of decay of maternal antibody against African horse sickness virus in South African Thoroughbred foals.
Authors: Crafford J E, Lourens C W, Gardner I A, Maclachlan N J, Guthrie A J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Maternal Antibody Decay in AHSV-Exposed Foals African horse sickness (AHS) remains a serious threat in endemic regions, with mortality rates exceeding 90% in naive populations, yet field data on antibody dynamics in vaccinated horse herds remain sparse. Crafford and colleagues investigated how maternal antibodies against African horse sickness virus (AHSV) transferred passively to foals from vaccinated dams, and critically, how quickly those protective antibodies declined over time in South African Thoroughbreds. Using serum samples collected at strategic intervals from foals born to mares vaccinated with the polyvalent modified live vaccine (MLV), the team tracked neutralising antibody titres and established decay rates for maternal antibodies. The findings revealed important windows of vulnerability as maternally-derived antibodies waned, informing evidence-based timing for foal vaccination programmes and helping practitioners identify the optimal age at which foals become susceptible to natural infection. This work has direct relevance for stud farms and competition yards operating in AHS-endemic areas, particularly in establishing vaccination protocols that minimise gaps in protection during the critical early-life period.
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Practical Takeaways
- •Foals born to vaccinated mares in African horse sickness endemic areas receive temporary passive protection; practitioners must understand when this wanes to time active vaccination appropriately
- •Maternal antibody decay rates should inform vaccination protocols for young foals in southern Africa to prevent gaps in immunity during high-risk periods
- •Vaccination status and timing of vaccination in breeding mares directly affects the level and duration of protection in offspring
Key Findings
- •Foals born to vaccinated dams receive passive maternal antibodies against AHSV through colostrum
- •Maternal antibody levels decline over time in foals, with rate of decay measured to determine protection window
- •Modified live virus vaccine generates antibody responses in pregnant mares that are transferred to offspring
- •Understanding maternal antibody kinetics is essential for determining optimal timing of foal vaccination in endemic areas