Vaccines for Broodmares in Late Gestation
By Heather Smith Thomas
The goal of every breeder is to have a strong, healthy foal. Preventative health measures to ensure disease protection for the foal include vaccination boosters for the mare before she foals. These boosters are very important for the mare during pregnancy, particularly during the last 4 to 6 weeks of gestation when she needs to be producing optimum levels of antibodies for her colostrum. The objectives of vaccination are to protect the mare’s health, fetal health, and provide good quality colostrum by the time she foals—to supply the newborn foal with adequate passive transfer of immunity.
For optimum antibody levels in colostrum, the mare must be vaccinated in late pregnancy. At that point her body can be producing the necessary antibodies at peak levels as she creates colostrum. You can’t wait until just before foaling, however, because the mare needs adequate time for her immune system to respond to the vaccine. This is why it’s best to try to give most boosters about a month before she foals. For specific recommendations, consult your own veterinarian.
Vaccination programs will vary from one region to another, depending on the most common diseases that the mare might encounter. Dr. Ahmed Tibary, Washington State University, says that mares can be vaccinated during pregnancy for influenza, rhinopneumonitis, tetanus, rabies, eastern and western encephalomyelitis, West Nile virus, botulism, and rotavirus. “In some areas where strangles is a problem, mares are also vaccinated with Streptococcus equi. If a new vaccination is contemplated (one that has not been previously included in the mare’s annual vaccination schedule), it should start before the third trimester of pregnancy so that enough time is provided for both the primary and booster vaccinations,” he explains.
Some veterinarians prefer to not give more than 4 vaccines at any one time. “Tetanus, rabies and eastern/western encephalomyelitis can be given in the fall of the year or at least 60 days before foaling, rhinopneumonitis vaccine can be given several times during the pregnancy, and influenza and West Nile virus vaccines should be given about 30 days before foaling (4 to 6 weeks before due date),” says Tibary.
Vaccination against Rhinopneumonitis (Equine Herpes Virus 1) is important for prevention of abortion due to this disease. “The traditional vaccine used for this purpose is a killed vaccine which needs to be given every 2 months, starting at either the 3rd or 5th month of pregnancy,” he says. Depending on the region and the risks, some people like to start at 3 months of pregnancy, while others start at 5 months. The vaccine is usually given to the mare at the 5th, 7th and 9th month of gestation.
“Some veterinarians have used the modified live vaccine for prevention of rhino abortions, without any negative effects, but this vaccine is not labeled for use in pregnant mares. The modified live vaccine seems to protect against both EHV-1 and EHV-4,” he says. There are recommendations for broodmare vaccination, set by the AAEP, but you need to check with your own veterinarian regarding the best vaccination program for your region, and for your particular mare. It is very important to keep the pregnant mare away from horses with unknown vaccination or health history.
