This document summarizes a study on the interference of maternally derived antibodies (MDAs) on foot-and-mouth disease (FMD) vaccination in calves. The study found significant variation in MDA levels between calves in a large dairy farm despite efforts to standardize colostrum administration. It also found that the farm's current vaccination program for calves starting at 2.5 months was appropriate, as delaying vaccination increased susceptibility to infection while earlier vaccination provided no added benefit. The study concludes that heterogeneity in MDAs must be considered to properly tailor vaccination strategies and protect both calves and adult cattle from FMD spread.

1. 1EuFMD | Open Session special edition | #OS20se
Claude HAMERS, DVM, PhD
Boehringer Ingelheim Animal Health, The Veterinary Public Health Center
France
MATERNALLY DERIVED ANTIBODIES TO FMD IN CATTLE: IS
INTERFERENCE ON FMD VACCINATION APPROPRIATELY CONSIDERED?

2. 2EuFMD | Open Session special edition | #OS20se
INTRODUCTION
• Little data available on Maternally Derived Antibodies (MDAs) interference on FMD vaccination and such
interference is largely underestimated.
• Particularly true with intensive FMD vaccination programs in place for adults (ie endemic countries),
resulting in high levels of MDAs in the young stock.
• We report here the results of a Post Vaccination Monitoring (PVM) study conducted in a large dairy herd
located in an endemic country.
MATERIAL & METHODS
• Study conducted in a “state of the art” dairy farm, in an FMD endemic country with high infection pressure.
Adults are vaccinated 4 times per year with Aftovaxpur. Calves are fed with high quality colostrum. To limit
MDA interference, calves are repeatedly vaccinated against FMD at a month interval, between 2.5 and 6.5
months of age (4 injections).
• To assess the calf vaccination program, MDA levels of calves were measured before vaccination. We then
compared the current vaccination to an earlier and to a later program. Comparisons were based on VNT
against O-Manisa, measured on serum samples taken at regular intervals.

3. 3EuFMD | Open Session special edition | #OS20se
RESULTS
• Average VNT at 2.5 months of age, before any vaccination, was 1.73 Log10.
• Despite the care regarding colostrum administration, a 10-fold difference was observed (1.24 Log10-2.29
Log10) between extremes
• The current vaccination program in place looked appropriate.
• No benefit to add an earlier vaccination. Delaying the vaccination program resulted in a period risk of
increased susceptibility to infection.
CONCLUSIONS
• MDAs frequently seen as a homogeneous parameter, managed on average antibody levels while
there can be huge differences in MDA levels.
• Receptivity of the calves to vaccination and susceptibility to infection vary accordingly.
• Adjusting the vaccination strategy of the calf category is critical, not only to protect calves, but
also to prevent that calves become a hotspot of dissemination for the production herd.
• Dairy herds have some specificities, among which optimal colostrum distribution. Heterogeneity of
the colostrum antibody levels would be even higher in beef cattle, resulting in a higher disparity of
FMD vaccine uptake.

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