Vaccine FAQ

Proper vaccinations are important for preventing dangerous diseases from infecting your horses, and for stopping spread to other horses. Your horse’s individual history, risk of exposure, region, and travel plans determine what vaccines are needed. Not all horses need all vaccines, but most horses need some vaccines. In Florida and the southeast, mosquito-borne illnesses are one of the most important things to vaccinate for. These diseases include the viruses that cause Eastern and Western Equine Encephalitis and West Nile Virus, which are almost always fatal in horses. These diseases do not spread horse to horse but are carried by mosquitoes. Any horse in any environment can contract these viruses. The mosquito season is year-round in Florida. We recommend vaccinating twice per year based on the duration of protection the vaccines have. Horses in colder climates may only need vaccinated once per year because their mosquito season is shorter. However, if they are shipping south they may need an additional booster about one month before traveling to ensure they are protected. Most of these vaccines are combined with Tetanus protection as well. Tetanus is an often fatal, very expensive disease to treat that is 100% preventable. It is caused by a bacteria that lives in the soil and is present in the feces of many animals, especially horses. Animals are usually exposed through a contaminated wound.

Another recommended vaccine is for Rabies. Rabies is identified in wild animals throughout North America every year. It most commonly affects raccoons, foxes and bats but can infect any mammal. Cases of rabies in horses are rare, but they can become infected if they are exposed to infected wild animals, and they can expose you to it as well. Rabies is always fatal. Never touch any wild animal that is behaving oddly, and protect all your pets by keeping their Rabies vaccines up to date.

Other needed vaccines are typically based on risk of exposure. Horses that show or travel frequently or are exposed to new horses routinely are at higher risk for Influenza and Equine Rhinopneumonitis, which is also known as Equine Herpes Virus. There are five types of Equine Herpes Virus. Types 1 and 4 are most common. Type 1 is typically identified as the most dangerous, as certain strains can cause severe neurologic disease as well as respiratory disease. Type 4 is more common and causes respiratory and reproductive diseases. Unfortunately, both Influenza and Equine Herpes are viruses that can mutate rapidly, but routinely vaccinating for them can decrease the symptoms and decrease further spread if you horse is exposed to a mutant strain. There are vaccines for Potomac Horse Fever, Strangles, Rotavirus, and Botulism as well. These vaccines are given based on your horses environment and the diseases present in surrounding areas.

Common Questions:

Why do I hear stories that some vaccinated horses still get sick?

True cases of these instances are very rare, and often get a lot of media attention when they happen. Outbreaks sometimes happen at horse shows, like the Influenza outbreak in Florida a few years ago. These populations of horses are typically well vaccinated and the cause is usually the result of the virus mutating. The immune system does not recognize it and the horse becomes ill, and can spread the mutant virus to other horses. When this happens, veterinarians and researchers identify the mutation and build a new vaccine to protect against that mutant strain, helping to prevent it from further spread. It is nearly impossible to predict how and when the viruses will mutate. Other reasons are typically less exciting. The horse may have missed or been late on a booster or annual vaccine, and did not have the protective antibodies and white cells needed. If the vaccine was purchased somewhere other than your veterinarian or shipped from a store or pharmacy and not handled correctly, it could have been damaged by heat or other exposure and lost its potency.

Why are there so many vaccine reactions?

In reality, true vaccine reactions are very rare. Most reported reactions from owners include fevers and muscle soreness. This is the normal response of the immune system to new viral and bacterial exposure and is not an adverse reaction. These symptoms are typically mild and transient and are similar to our own responses to vaccines (we just do not remember them because we got them when we were younger). If your horse becomes colicy or goes off feed, a short duration of NSAIDs typically resolves their symptoms. Seeing your horse uncomfortable is not pleasant, but it means their immune system is doing what it should. What does a true vaccine reaction look like? Severe vaccine reactions typically result in severe colic symptoms, trouble breathing, profuse sweating, severe muscle soreness or panicky behavior that happens within minutes of administration. Emergency medications may be needed, so call your veterinarian and let them know, and make sure you or your veterinarian call the manufacturer and report the adverse advent if it happens. If your horse is prone to having severe vaccine reactions make sure you have documentation from your veterinarian, as many show organizations and clubs will make accommodations.

Can’t we just test titers instead of vaccinating?

Titers measure one portion of the adaptive immune system, called humoral immunity. This is the part of the immune system that produces antibodies that attach to viruses, bacteria or other antigens and inactivates or marks them for destruction. The other part is called cell-mediated immunity. This part includes all the white cells that recognize and kill or inactivate viruses, bacteria, or other circulating antigens and recruit other cells to help. Both humoral and cell-mediated immunity work together and are needed to mount an adequate immune response. Unfortunately, with titers we do not get any measure of how well the cellular side is working, or if it is at all. The horse may have circulating antibodies, but the cells needed for an adequate response may not be ready or primed to respond, putting your horse at risk for infection. Unfortunately, we just do not know how many circulating antibodies are needed to indicate that the cellular side is ready to respond, or if it is at all. Further research may help us find the answer some day. Until then, we know that appropriately given vaccines are protective and safe for most horses and are our best bet for keeping your horse protected and limiting the spread of disease.

Have more questions? Don’t hesitate to ask.

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