Equine Vaccinations

Core Vaccines:
“Core” vaccines protect against diseases that are found throughout the United States and AAEP recommends all horses receive these vaccines.

Tetanus
Tetanus is caused by a spore forming bacteria know as Clostridium tetani. This bacterium is present in the soil and horses are exposed through contamination of puncture wounds, incision sites, lacerations, and the umbilicus in foals. Horses are extremely susceptible to tetanus and clinical signs include progressive muscle spasms and stiffness, difficulty moving and eating, noise sensitivity, and in severe cases convulsions and death from respiratory failure. Tetanus is very difficult to treat and often results in death. If caught early, high doses of antibiotics and supportive care may be able to save the horse. Vaccination is highly effective in preventing disease and all horses should be vaccinated annually. Foals require a 3 dose series with 4-6 weeks between the first two vaccines and the third at 10-12 months of age.
Rabies
Rabies is caused by a virus that is 100% fatal and causes severe neurologic symptoms. Horses can contract rabies by being bitten by a rabid animal such as a skunk, raccoon, fox, or bat. It is recommended that all horses be vaccinated annually for rabies. Foals require an initial vaccine (no earlier than 6 months of age) with a booster in 4-6 weeks and annually after that

Eastern and Western Equine Encephalitis (EEE and WEE)
EEE and WEE are viral infections transmitted via mosquitoes that feed on infected birds both diseases can also affect humans however transmission from horses to humans does not occur. Clinical signs include fever, inappetance, weakness, seizures, and circling, excitability, and often death. EEE is 90% fatal and WEE is 20-40% fatal. There is no effective treatment, supportive care to manage the symptoms is the most that can be done. Vaccination is very effective at preventing disease and every horse should be vaccinated annually prior to the onset of mosquito season. In areas of very high mosquito populations or year round mosquito activity, horses should be vaccinated every 6 months to provide adequate protection. Other ways to help protect against disease include keeping barn lights off at night to prevent mosquitoes from gathering, getting rid of standing/stagnant water where mosquitoes breed, and appropriate use of fly spray and fly sheets during peak insect season.
West Nile Virus
West Nile Virus (WNV) is found throughout the United States and horses represent ~97% of non-human mammalian cases of WNV. It is transmitted to horses from avian reservoirs via mosquitoes it is not directly contagious from horse to human but the infected mosquito can transmit the disease to both horses and humans. Clinical signs are primarily neurologic, including fever, weakness, paralysis, head pressing, gait abnormalities, and other neurologic signs. Vaccination is recommended annually in all horses with the initial vaccine requiring a booster in 4-6 weeks. Foals require a 3 dose series with 4-6 weeks between the first two vaccines and the third at 10-12 months of age. In areas of high risk the vaccine may be boostered every 6 months to provide adequate protection.
The following vaccines are not always recommended for all horses. They are recommended for horses with an increased risk for the disease, such as horses that travel a lot, broodmares, horses at large boarding barns where animals frequently come and go, young animals, and horses living in swampy areas.
Equine Influenza (Flu)
Equine influenza is caused by an influenza virus and is one of the most common causes of infectious respiratory disease in horses. Horses ages 1-5 years old are the most susceptible but any age horse can be affected. Frequent contact with many horses is another risk factor. This disease is highly contagious and can spread through the air when sick horses cough. Clinical signs may include a cough, fever, lethargy, anorexia, nasal discharge, and increased respiratory effort. According to AAEP all horses should be vaccinated unless they lived in a closed and isolated facility (meaning they do not travel at all and have no contact with horses that live at other facilities). This vaccine requires two boosters initially in foals and then every 6 months for animals at high risk and every 12 months for animals with low risk.
Equine Herpes Virus 1 +4
Equine Herpes Virus (EHV), also known as rhinopneumonitis, causes respiratory disease in horses and can cause abortions in pregnant mares. Young horses are most commonly affected and clinical signs are the same as for equine influenza. Because these viruses are so common, most adult horses have been exposed and have some level of natural immunity, thus adult horses do not usually develop serious respiratory disease. EHV is spread via coughing horses, contact with contaminated surfaces such as buckets, and also by contact with aborted fetuses. Horses at high risk of contracting EHV should be vaccinated at 6-month intervals. In foals a primary series of 3 doses is required. Since infection with this virus can cause abortions, pregnant mares need to have a high level of protection. Vaccination at months 5, 7, and 9 of pregnancy is recommended to maintain protective antibody levels.
Strangles
Strangles is caused by bacteria called Streptococcus Equi. It primarily affects young horses but can cause disease in any age horse. This disease is highly contagious and it is transmitted via direct contact with an infected horse or a subclinical shedder. Indirect transmission can also occur when an unprotected animal has contact in contaminated water troughs, feed tubs, stalls, trailers, clothing, and even a person’s contaminated hands. Signs of strangles include a fever, difficulty eating, thick nasal discharge, very sore throat, and large swollen lymph nodes in the throat latch. Once this disease is brought into a large boarding facility it tends to pass slowly from horse to horse, making lots of extra work for everyone and ruining show plans for the exposed and affected animals. Unless the affected horse is very sick, antibiotics are not indicated. Supportive care and quarantine from healthy horses is essential. Blood tests and nasal swabs are needed to make a definitive diagnosis of strangles, which gets expensive very quickly. Vaccination is recommended for horses that show or travel frequently and for horses boarded at barns where animals are often coming and going. There are two forms of the vaccine, injectable and intranasal, the scheduling of vaccination depends on which product is used.
Potomac horse fever (PHF)
Potomac horse fever is caused by the bacteria Neorickettsia risticii and is transmitted to horses via ingestion of dead and infected water dwelling flies like the may fly and dragonflies. These flies don’t live very long and can die in hay and on pasture where your horse can ingest them along with the PHF bacteria. Signs of PHF include severe fever and diarrhea. PHF is treatable with antibiotics when diagnosed early, however it can progress rapidly and in severe cases can cause laminitis and death. Most PHF infections occur between late spring and early fall, therefore vaccinations should be given prior to this high-risk season. The initial vaccine requires a booster 3-4 weeks later and then every 6-12 months after that. In areas with a high prevalence of PHF the vaccine should be boostered every 6 months.
Venezuelan Equine Encephalitis (VEE)
VEE is very similar to EEE and WEE however with this virus horse to human transmission can occur. VEE is a foreign animal disease, meaning it is something we haven’t seen in the United States for over 35 years. It does occur in South and Central America thus horses living in areas of Southern Texas, California, Louisiana, Mississippi, Alabama and the West Coast of Florida are at the most risk for natural VEE infection. This vaccine is not considered “core”, but because horses often travel and because show horses are exposed to so many other animals from all over, it is something we routinely vaccinate for. VEE comes in a vaccine combination with EEE, WEE, and often tetanus so there is no additional injection or cost associated with vaccinating for VEE.
Typical vaccination schedule for foals born from vaccinated mares:
4-6 months of age: Tetanus, WNV, Rabies (No earlier than 6 months), EEE/WEE/VEE, Flu, EHV
4-6 weeks later, typically around 7 months: Tetanus, WNV, Rabies, EEE/WEE/VEE, Flu, EHV
10-12 months of age: Tetanus, WNV, EEE/WEE/VEE, Flu, EHV PHF and Strangles vaccines are given once the core vaccine schedule has been completed.