VACCINATION GUIDELINES

Core Vaccines:

The core vaccines are ones that all horses should receive. Their safety and efficacy has been proven, and they demonstrate a high level of patient benefit with a very low risk.

• Tetanus – This disease is caused by spore-forming bacteria called Clostridium tetani, which are present in the equine intestinal tract, feces and also in the soil. Tetanus is not an infectious disease but occurs when the bacteria enters tissues, such as puncture wounds or open surgical incisions that provide an anaerobic environment. A neurotoxin then gets released, leading to a frequently fatal rigid paralysis. Horses are exquisitely sensitive to C. tetani and horses of any age are at risk of developing this disease. All horses should be vaccinated annually against tetanus. A booster is required if the horse received a penetrating injury or prior to surgery if not vaccinated in the last 6 months.
• Rabies – Rabies is a neurologic disease caused from a bite from an infected mammal, such as a raccoon, fox or bat. The virus migrates via the nerves to the brain and causes fatal encephalitis. Rabies vaccination is recommended in horses for all areas in which it is endemic in the wildlife population, which includes most of the Eastern United States. All horses should be vaccinated annually for Rabies. *Rabies vaccine must be administered by a licensed veterinarian in order to have proof of vaccination.*
• Eastern/Western Equine Encephalomyelitis – EEE/WEE is transmitted primarily by mosquitoes. Wild birds and rodents serve as natural reservoirs for these viruses and are not affected like horses which are terminal hosts. Humans are also susceptible to these diseases when the virus is transmitted to them by infected mosquitoes and although horse-to-human transmission is unlikely, this is a reportable disease due to the potential risk. In horses, EEE has a higher mortality rate approaching 90%. We recommend vaccination annually for EEE/WEE in the spring, prior to mosquito season. Horses living in or traveling to areas where mosquitoes are prevalent year round, such as Florida, should be vaccinated at least twice yearly.
• West Nile Virus - West Nile virus (WNV) is also transmitted by mosquitoes, from avian reservoir to horses, humans and a number of other mammals, potentially causing life threatening encephalitis. Horses and humans are considered to be dead-end hosts for WNV, which means the virus is not directly contagious from horse to horse or horse to human. All horses should be vaccinated annually for WNV in the spring, prior to mosquito season. However, as mentioned for the EEE/WEE, horses living in areas where mosquitoes are active year round should be vaccinated twice yearly.

Recommended/Risk Based Vaccines:

These vaccines are recommended based on geographic prevalence of a disease and/or on the management of your horses. Some horses would be well protected with fewer vaccines, but depending on travel, performance and regional prevalence of certain diseases, there may be additional diseases that the core vaccinations did not cover. Each horse owner or farm should set up a plan tailored to their needs based on your veterinarian’s recommendations.

• Equine Herpesvirus - There are different types of equine herpesvirus; the most common types are EHV-1 and EHV-4. Clinical signs seen with EHV-1 are respiratory disease, abortion and neurologic disease. With EHV-4 infection, respiratory disease is seen most commonly but rarely neurologic disease can occur. While all ages are affected by the disease, horses at the greatest risk for developing the disease are those that frequently have contact with new horses. Most horses are exposed in some point in their lives (usually when their young), but it can become dormant and reactivate during times of stress. No vaccines currently on the market prevent the neurologic form of the disease, but vaccination is recommended to prevent abortion and reduce the severity and spread of the respiratory disease.
• Influenza – Equine influenza is caused by a virus and Equine Influenza A type 2 is endemic in the American horse population. Younger horses are more commonly affected by the influenza virus. It is a highly contagious virus and will rapidly spread through a group of horses. The clinical signs consistent with this disease are high fever, clear nasal discharge, loss of appetite, depression and a dry deep cough. In uncomplicated cases, the disease usually lasts 2-10 days. Affected horses will remain infectious for 3-6 days after resolution of clinical signs. Quarantine of new horses for at least 14 days or vaccination prior to potential exposure to the virus can greatly decrease the likelihood of infection. Almost all horses should be vaccinated against influenza, but a vaccination schedule for influenza can vary from every 90-120 days if your horse shows or travels frequently, to nothing for a solitary horse on a farm.
• Potomac Horse Fever - This disease is caused by Neorickettsia risticii (formerly Ehrlichia risticii) which is carried by insects that are ingested inadvertently by horses. The disease is seasonal, occurring between late spring and early fall in temperate areas, with most cases in July, August, and September. Clinical signs are variable but may include: fever, mild to severe diarrhea, laminitis, and mild colic. Uncommonly, pregnant mares infected with N. risticii can abort mid-gestation. Cases of Potomac Horse Fever have been identified in our practice area, therefore we recommend twice yearly vaccination, once in the late spring and again in early fall. Although the vaccine may not prevent the horse from getting the disease, it is believed to reduce the severity of clinical signs.

The information above is consistent with the ‘Guidelines for The Vaccination of Horses’ established by the American Association of Equine Practitioners. For further details visit http://www.aaep.org/vaccination_guidelines.htm.