Passive transfer of maternal immunoglobulin isotype antibodies against tetanus and influenza and their effect on the response of foals to vaccination.
Authors: Wilson W D, Mihalyi J E, Hussey S, Lunn D P
Journal: Equine veterinary journal
Summary
# Editorial Summary: Maternal Antibodies and Foal Vaccination Timing When mares receive booster vaccinations in late pregnancy, they transfer high levels of influenza and tetanus-specific IgG antibodies to their foals via colostrum—a protective measure that paradoxically undermines vaccination responses in young animals. Wilson and colleagues (2001) quantified these maternal antibody titres in foals from birth through 26 weeks of age and assessed vaccination responses at 3, 6, and 12 months, measuring specific IgG subisotypes (IgGa, IgGb, and IgG(T)) and IgA responses. Maternal tetanus and influenza IgGa antibodies declined with half-lives of approximately 28–29 days, whilst IgGb antibodies persisted longer (35–39 days), yet all remained detectable at 26 weeks despite vaccination attempts; critically, foals vaccinated at 3 months showed no meaningful immune response regardless of booster doses, whereas vaccination at 6 months and yearling age generated robust IgG subisotype responses. These findings have direct implications for vaccination protocols: commencing primary immunisation before 6 months of age in foals born to vaccinated mares is largely ineffective and wasteful of resources, supporting the authors' recommendation to delay vaccination until at least 6 months when maternal antibody interference has waned sufficiently to permit adequate seroconversion.
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Practical Takeaways
- •Do not vaccinate foals against tetanus or influenza before 6 months of age if the dam received booster vaccinations during late pregnancy—maternal antibodies will block vaccine response
- •If vaccinating foals younger than 6 months is necessary, expect to require 1–3 additional booster doses at older ages to achieve equivalent titres to foals vaccinated at 6+ months
- •Yearlings and 6-month-old foals show reliable vaccine responses; plan primary vaccination schedules accordingly based on the foal's age and dam's vaccination history
Key Findings
- •Maternal IgG antibodies against tetanus and influenza are passively transferred via colostrum and inhibit foal response to inactivated vaccines, remaining detectable at 26 weeks of age
- •Influenza IgGa antibodies have significantly shorter half-life (27.0 days) compared to IgGb (39.1 days; P<0.005), with tetanus antibodies declining similarly over 28-35 days
- •Three-month-old foals failed to mount detectable IgG responses to either tetanus or influenza vaccine, whereas 6-month-old and yearling foals demonstrated significant increases in IgG subisotype titres
- •Primary immunisation of foals born to vaccinated mares should not commence before age 6 months to avoid maternal antibody interference with vaccine efficacy