Protection of a foal against infectious diseases begins before birth. The goal of prepartum vaccination is to stimulate the immune response of the mare to produce antibodies which will eventually be sequestered or concentrated in the colostrum. Ingestion of colostrum from vaccinated mares during the first 12 to 24 hours of a foal’s life results in the passive transfer of high levels of maternal antibodies to the foal. Uptake of maternal antibodies through nursing is critical for immune protection of the foal from infectious diseases during the first few months of life until the foal can develop its own antibodies. Maternal antibodies may be present in the foal for 3-4 months in most cases and up to 6 months or more in some foals.
In Australia there are three main vaccinations that are commonly used for pregnant mares. These vaccinations are:
- 2 in 1 for Tetanus/Strangles
- Equine Herpes Virus (EHV)
When deciding when to vaccinate a pregnant mare, the vaccination history of the mare needs to be considered to ensure that the most suitable process is followed. Below are some guidelines that can be used:
Fully Vaccinated Mares:
- Tetanus/Strangles – Previously vaccinated mares that are up to date with their vaccinations only require a single Equivac 2 in 1 booster to be administered 4-6 weeks prior to foaling.
- Salmonella – Previously vaccinated mares that are up to date with the vaccinations require a single Salmonella booster 4-6 weeks prior to foaling.
- Equine Herpes Virus (EHV) – pregnant mares should receive a Duvaxyn EHV booster at the beginning of the 5th, 7th & 9th month of pregnancy to help prevent abortion caused by EHV.
Uncertain Vaccination History or Unvaccinated Mares:
- Tetanus/Strangles – Unvaccinated mares require a Equivac 2 in 1 booster, repeated after 4 weeks. Ideally a booster vaccination should also be given 4-6 weeks prior to foaling.
- Salmonella – Unvaccinated mares require a Salmonella vaccination, repeated at 4-6 weeks. Ideally a booster vaccination should also be given 4-6 weeks prior to foaling.
- Equine Herpes Virus (EHV) – Vaccinate pregnant mares at the beginning of the 5th, 7th & 9th month of pregnancy.
It is important to remember that vaccination programs will differ for individual needs & situations. The above are recommendations for a vaccination program to protect against Tetanus, Strangles, Equine Herpes Virus and Salmonella in pregnant mares, which will allow maternal antibodies to be passed on to the foal.
Note: In some areas of Australia, some veterinarians also recommend that pregnant mares be vaccinated for Hendra Virus. The Australian Pesticides and Veterinary Medicines Authority (APVMA) has ruled the vaccine to be safe in pregnant mares and their unborn foals. Your veterinarian will be able to advise you of the vaccination process and if vaccinating your mare for Hendra virus is necessary.