As foals grow and approach weaning age, it's time to think about giving them their booster shots. • Photo by Annika Treial via Unsplash.

5 Tips for Vaccinating Foals & Weanlings

If you have a foal on the ground this year, you probably know that within a couple hours after birth, it should have been up and nursing its dam. You may not realize, though, that those first meals in the foal’s life are crucial in determining the protection he or she will have from disease.

While the dam helps build the foal’s immunity through her milk, as the foal ages, it will become your responsibility as the owner to continue to protect your foal from viruses, bacteria and pathogens with a proper vaccination schedule. Quarter Horse News spoke with Dr. Francisco Alvarez, an equine veterinarian in Houston, to learn how to vaccinating foals can help them develop the best possible immune system so they can turn into healthy adults.

1. Provide Quality Colostrum

Foals are born “immunologically naïve,” which means that without the immunoglobulins, or proteins, they receive from their mother’s colostrum, their existing immune system can’t function properly. These antibodies are what will protect the foal from disease until it reaches the age where it can start safely receiving vaccines. For this reason, foals must nurse within one to two hours after birth.

“These proteins are super important for the foal to fight off infections early in its life,” Alvarez said. “If the foal ingests the colostrum appropriately, it will use these immunoglobulins for the first four to six months of life.”

As the immunoglobulins are produced in the mare, the quality of the colostrum the foal receives begins with its dam. A mare that is up-to-date on her vaccinations will produce a much higher quality colostrum than one that has not received any pre-foaling vaccines.

2. Help Foals Born of Unvaccinated Dams Build Immunity

Mares should be administered pre-foaling vaccines one month before the foal is due. If a mare is not vaccinated, her foal should be tested during its new foal exam, which happens within 24 hours after birth, to see what kind of immunity it received.

“If the test reveals that not enough immunity was passed from the dam to the foal, your veterinarian might recommend a plasma transfusion,” Alvarez said. “This is another way foals can receive immunity. Some of the plasmas that are used for transfusion can be hyperimmunized, meaning that the horse that donated the plasma was vaccinated with different bacterias or viruses to produce plenty of immunity to those pathogens.”

If a plasma transfusion can’t be done, vaccinating foals out of unvaccinated mares should be done earlier than other foals and more frequently. This will help them obtain acquired immunity so they can produce their own immunoglobulins.

3. Follow Up Vaccines with Boosters

Immunity received from a vaccinated dam should last a foal about four to six months. At that point, they will need to receive their first round of core vaccines, followed by booster shots four to six weeks later, then at 10 to 12 months. Horses are considered fully vaccinated after receiving three doses on that recommended schedule, according to the American Association of Equine Practitioners (AAEP).

“Remember to take into consideration vector season, which is mosquito season,” Alvarez. “In other words, boost before the beginning of mosquito season. In the Southeastern United States, it is recommended that foals start vaccination at two or three months of age.”

4. Protect with the Core Vaccines

“Core vaccines are vaccines that have been recommended by the AAEP for all horses to be given,” Alvarez said. “They are very effective against diseases that any horse sitting alone in a pasture can come down with, diseases that are endemic to a region or those that pose a public health issue or significance.”

One core vaccine for horses is the rabies vaccine. Rabies is zoonotic, meaning it can be transmitted to people, and is always fatal. The AAEP recommends foals of unvaccinated mares receive the rabies vaccine at four to six months of age, followed by annual revaccination. Foals of vaccinated mares should receive a two-dose series, to address the potential for maternal antibody interference, followed by annual revaccination.

Other core vaccines include Eastern and Western Encephalomyelitis and West Nile, which are transmitted by a vector like mosquitos. Rounding out the core vaccines is the Tetanus shot. Tetanus is an often-fatal disease caused by the bacterium Clostridium tetani, which horses are susceptible to if they have an open wound or undergo surgery.

5. Don’t Under Vaccinate

Even if your foal grows up without ever stepping foot in a trailer, there are pathogens it could be exposed to right at home. For this reason, vaccinating foals is key to producing a healthy horse, even one that’s a homebody.

“Bacterias such as Rhodococcus and Clostridium are ubiquitous, meaning they are everywhere in the environment,” Alvarez said. “This is why it is very important for foals to develop a good immune system and to be placed in clean environments to minimize the chance of exposure.”

Certain geographical regions, populations and individuals are considered at-risk to certain diseases, like anthrax, strangles and Equine Influenza, due to their location or proximity to other horses. It sounds scary, but as long as you work with your veterinarian to formulate the correct vaccine protocol for vaccinating foals at your farm, your foal should grow up protected whether you plan to haul it regularly to horse shows or just spend your time riding around your property.