Every situation is different, and discussing your specific horse with a veterinarian is the best way to make a plan for vaccinations. However, the basic "core" vaccinations that every horse needs at least yearly are: Rabies, Tetanus, Eastern/Western Equine Encephalitis, and West Nile Virus. These diseases are serious, life threatening and/or very costly to treat, and are easily prevented with vaccination. Additional vaccinations that may be recommended include the contagious respiratory viruses (Influenza and Rhinopneumonitis) and the contagious respiratory disease Strangles. Depending on environment, Potomac Horse Fever and/or Botulism vaccinations may be recommended. Finally, in breeding stock, Equine viral arteritis vaccination may be necessary.
Brief summaries of the diseases we vaccinate for, how often they should be given, and when to give them:
Rabies: An untreatable neurologic virus. Rabies is present in the fox, skunk, racoon and bat population generally, and is transmitted when saliva from an infected animal enters a wound or mucus membrane (bite wound, eyes, mouth, etc). It is always fatal, and it is transmissible to people. The only prevention is vaccination, given yearly. It does not matter what time of year the vaccine is given.
Tetanus: A bacteria that gains access to the body through a wound. The toxins produced by this bacteria cause a rigid spasm in the muscles ("lockjaw" or "sawhorse stance"). This disease is debilitating, very costly to treat and can be fatal. Because of their environment, horses are considered at high risk for this disease. They should be vaccinated yearly. A booster vaccination should be given if a wound occurs greater than 6 months after vaccination.
Eastern/Western Equine Encephalitis: Two strains of the same virus, transmitted by the bite of an infected mosquito. This disease, like Rabies, affects the nervous system, and is often fatal. It is not transmissible directly from horse to human, but the same disease can be transmitted to humans through a mosquito bite. In this area, yearly vaccination in the spring (before mosquitoes emerge) is sufficient.
West Nile Virus: Similar to EEE/WEE (above), this virus is transmitted by the bite of a mosquito and affects the nervous system. It is often fatal, and very costly to treat. Horses that survive may be left with permanent deficits. Yearly vaccination in the spring (before mosquitoes emerge) is highly protective against the disease.
Influenza: A highly contagious virus which causes an irritating respiratory infection. Not generally fatal but can be debilitating, especially in younger horses. Can be compounded by inhaled irritants from trailering, dusty arenas; horses that travel and are exposed to many different horses are especially at risk. The intranasal form of this vaccination is protective for 6 months, because it targets the nasal mucosa which is the primary defense against the disease. The intramuscular form of the vaccine lasts only a few months, and may be less protective. Horses should be vaccinated about a month before travelling or showing, to allow their immunity to be at the highest level when they are at risk.
Rhinopneumonitis (now known as Equine Herpes Virus): Similar to influenza, a highly contagious respiratory virus. Additionally, some strains can cause abortions in pregnant mares, and rarely will cause a severe (often fatal) neurologic disease. The vaccine is short lasting (about 3 months) and should be boostered about a month before travelling or exposure to other horses. Horses at high risk should be vaccinated every three months. Horses at low risk can often be given the vaccination once or twice yearly before exposure to high risk situations. Pregnant mares should be vaccinated with an inactivated ("killed") form of the vaccine at 5, 7, and 9 months of gestation, to help prevent abortion due to this virus.
Strangles: A highly contagious, debilitating bacterial infection caused by the bacteria Streptococcus equi equi. This disease classically causes abscesses in lymph nodes near the throatlatch, as well as severe yellow nasal discharge. Rarely, internal abscesses (in the abdominal or chest cavities) may occur which cause severe complications. The intranasal form of this vaccine is more effective (and safer) than the intramuscular form, and should be given to high risk horses once or twice yearly.
Potomac Horse Fever: A bacterial infection caused by eating infected insects found near marshy land - can cause diarrhea, fever, and/or laminitis. This disease is not very common in this area, but is seen more regularly east (Syracuse area) and south/east (PA). The vaccine is not 100% protective but will often lessen the severity of the disease. An unvaccinated horse may develop severe enough laminitis to need to be euthanized, while vaccinated horses may only experience diarrhea and warm feet, for example. The vaccine should be given once or twice yearly. If once yearly, give in spring. If twice yearly, give in spring and fall.
Botulism: A bacterial toxin that causes severe muscle weakness. The toxin is usually ingested while eating contaminated hay (likely in round bales or bales which contain dead animals). The disease is very costly to treat and is often fatal. A yearly vaccination (any time) is effective.
Equine Viral Arteritis: An infection spread by mating. Vaccination is often required in breeding stock, given 2-4 weeks before the breeding season to stallions, and yearly to mares when they are NOT in foal. At the time of the first vaccination, horses need to be tested and confirmed negative for the disease.