Page 24 - Canada Spring 2019

VACCINATING BROODMARES
AND FOALS
Vaccination is one of our best tools for protecting
young foals from disease, and the best protection for foals begins with vaccinating brood- mares at strategic times during pregnancy. This results in passive transfer of antibodies to the foal through colostrum, if the foal ingests an adequate amount of colostrum shortly after birth. It is also important to vaccinate preg- nant mares against diseases that could cause abortion.
VACCINATING MARES
Dr. Katherine Wilson (Clinical Assistant Professor, Large Animal Medicine, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia), says that during pregnancy most mares get vaccinated for Equine Herpes Virus 1 (EHV-1) which can cause abortion in mares. “Broodmares are generally vac- cinated at 5, 7 and 9 months of pregnancy. EHV-1 typically causes abortion late term, in mares. This virus can also be latent in many horses, so the mare doesn’t have
to be exposed to an outbreak of respiratory disease to get it and abort,” she says.
“The mare can either have a latent infection or be exposed to the disease or pick it up from aborted placentas or fetuses. Pregnant mares can easily be at risk for this disease, so we vaccinate them dur- ing pregnancy,” says Wilson.
“The other important thing regarding vaccination for mares is to vaccinate them during the last 4 to 6 weeks of pregnancy with core vaccines (against the diseases for which all horses could be at risk). These include eastern and western encephalitis, tetanus, West Nile, influenza, and rabies, and another vaccination booster for EHV-1. These are diseases that foals may be exposed to in the first months of life, and if we vaccinate the mares during the last 4 to 6 weeks of gestation, that gives the mare time to produce antibodies and have a high titer. This enables the mares to produce a high level of antibodies in their colostrum,” she explains. “We are essentially try- ing to boost the mare’s antibody titers so she can pass this protec- tion to the foal via the colostrum.”
There are some other vaccines that are risk-based, that target certain foal diseases. If foals are at high risk for encountering and
by Heather Smith Thomas
developing these diseases, you could vaccinate the mares—so they can pass the antibodies to the foals in their colostrum. “One of these diseases is botulism, which can
affect foals. Another is rotavirus, which causes diarrhea in young foals. Whether or not you vaccinate the mare will depend on potential exposure of the foal and the disease history on the farm.”
There are some other diseases that foals may be at risk for that have no vaccines available, including salmonella and clostridia infections in the GI tract. “If necessary, a foal could be given plasma after it’s born and some of these products might contain antibodies that may help prevent salmonella or clostridia.”
Dr. Katherine Wilson, a Clinical Assistant Professor of Large Animal Medicine,
says that vaccinating mares for Equine Herpes Virus-1 (EHV-1) is especially important since it can cause abortions in mares. Vaccinating with
core vaccines in the last 4-6 weeks of gestation will give the mare time to produce a high level
of antibodies in her colostrum.
24 SPEEDHORSE CANADA, Spring 2019
EQUINE HEALTH