Keeping track of your breeding stock’s vaccination schedules can be confusing. Dr. Charles Love offers tips to optimize your broodmares’ vaccinations.
By Megan Arszman
Vaccination schedules can be bewildering, especially for breeders. Scheduling a certain vaccination at the wrong time could have a negative or even dangerous result. The American Association of Equine Practitioners (AAEP) helps horse owners and breeders navigate this complicated health-care routine.
Core vaccinations, including those for the diseases primarily transmitted via mosquitoes (Eastern and Western Equine Encephalomyelitis [EEE/WEE] and West Nile Virus [WNV]), as well as tetanus and rabies, should be given at regularly scheduled times and kept updated. (Read more about these vaccines in the April Reiner).
Risk-based vaccinations should also be included in your horse’s regimine, after a discussion with your vet about what’s necessary in your area and in areas where you might travel. These include anthrax, botulism, equine herpesvirus, equine influenza, leptospirosis, Potomac horse fever, rotaviral diarrhea, snakebite, and strangles.
Timing of vaccinations is crucial for pregnant mares. Early gestation is an especially sensitive time when it comes to potential complications from a vaccine, said Charles Love, DVM, PhD, Professor of Equine Theriogenology in the Department of Large Animal Clinical Sciences at Texas A&M University. But, the list of vaccines necessary early in the pregnancy is limited.
“It’s not close to when the foal is due, which is when you want the maximum antibody response,” Love explained. “So, there isn’t very much to do early in gestation.”
Love and AAEP recommend all vaccinations be updated prior to breeding, especially since there’s an increased chance for abortion if a mare contracts an infectious disease. Core vaccinations should be given prior to breeding, and boosters should be administered one month before anticipated foaling to increase the antibody levels in the mare’s colostrum. That colostrum provides essential protection from disease until a foal can be vaccinated.
One vital vaccine for broodmares, that for equine herpesvirus (known as EHV or rhinopneumonitis virus), should be given three times during the gestation period. This vaccine can cause abortions and can cause respiratory tract infections in young horses, so it should be scheduled for months five, seven, and nine of the mare’s pregnancy.
Give your mare pre-foaling vaccines four to six weeks prior to foaling to induce an antibody response. Ask your veterinarian about proper vaccination protocols in your region for EEE/WEE, WNV, EHV, botulism, tetanus, equine influenza, rabies, and rotavirus (given in a three-dose series, one month apart, starting in the eighth month of gestation).
AAEP strongly recommends that only killed or inactivated vaccines— not live vaccines—be given to broodmares. While you should always consult your vet about vaccine-related choices, maintaining open discussion is especially important throughout your mare’s pregnancy.
Foals are initially protected by the “magic milk” of their mother’s colostrum. Approximately 12 to 18 hours after birth, your veterinarian should run an IgG blood test to ensure that the antibodies supplied via colostrum are being sufficiently absorbed by the foal. If there are any issues, your vet will work with you to help the foal. Because of the antibodies naturally supplied in colostrum, a foal won’t need to receive any vaccinations until he’s four to six months of age.
“You don’t want to give foals vaccines prior to this time period because the vaccination will compete against the antibodies from their mother,” Love explained.
For the majority of core vaccines, foals will receive their first vaccinations in a series of shots. This includes tetanus, strangles, EEE/WEE, WNV, botulism, EHV, and equine influenza. Rabies, leptospirosis, and Potomac horse fever are given in a two-dose series starting at six months. Colts are vaccinated against equine viral arteritis (EVA) anytime between six and 12 months of age.
“The series of vaccinations is to help the foal’s system work up to a higher titer,” Love shared. “Too much all at once can harm the foal.”
Unlike broodmares, breeding stallions don’t need additional vaccinations, with the exception of annual testing and vaccination for equine viral arteritis (EVA). EVA can affect the stallion’s semen quality in terms of sperm motility, concentration, and abnormalities, which can lead to temporary infertility for up to four months. It’s also a disease that can be passed to a broodmare, which may cause placental and fetal damage and potentially result in an abortion.
Most countries require EVA testing for stallions before shipping semen internationally. A stallion undergoes testing prior to the time of vaccination to ensure he’s negative for the disease. After the test results confirm he’s negative, the stallion can be vaccinated. All testing and vaccination records should be kept in the stallion’s files, Love recommended, for easy access when shipping semen.
“Vaccination schedules can change from year to year,” Love cautioned. “I encourage breeders and owners to use the AAEP website (aaep.org) to stay informed. Vaccinations can be a little confusing, but those guidelines are put online by experts.”
As always, vaccination and proper care for your breeding herd go hand in hand. If you have multiple pregnant broodmares during the same season, consider keeping them in groups according to their stage of gestation. Separate those groups of mares from horses of other ages, especially those that are hauled off property for shows and events.