April 2013 Articles

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Equine Vaccinations

Equine Vaccinations Dr. Neely Walker, LSU Ag Center

Vaccination is considered the most cost-effective method of preventing infectious diseases; however, vaccines do have limitations. It is important to recognize that vaccines are not 100% effective and cannot prevent all horses from becoming ill. Generally, vaccines need to be administered to a horse at least 2-4 weeks prior to shipping to a new location, hauling to an event or being exposed to new horses. This ensures that the horse has enough time to generate enough antibodies for protection from the diseases. That being said, there is no “vaccine schedule” that works for all horses and all farms. For the most complete protection for your farm and your horses, consult your veterinarian for a core vaccine program that will suit your specific needs.
Core Vaccines Tetanus – causes a progressive, stiff paralysis that can be 80% fatal if not treated; caused by the bacteria Clostridium tetani, which are found in abundance in the soil where horses live. These bacteria will infect wounds and release a potent neurotoxin. West Nile Virus (WNV) – a neurologic disease that affects horses and people; causes encephalomyelitis. This disease is transmitted by mosquitos and is not contagious; however, one-third of all horses who contract WNV will die, and approximately 40% of those who survive will have residual neurologic effects. Rhinopneumonitis (Rhino) – Equine Herpes Virus 1 and 4 (EHV-1 & EVH-4) is a respiratory disease that is highly contagious and may persist in the environment for two weeks. This virus causes a variety of clinical forms including neurological disease, upper respiratory disease, abortion, and weak and stillborn foals. There is no vaccine for the neurologic form of the disease. Strangles – is caused by the bacteria Streptococcus equi and is highly contagious and persistent in the environment. These bacteria cause high fever, mucopurulent nasal discharge, and swelling and abscesses of the lymph nodes of the head and neck. Intramuscular and intranasal vaccines are available. Western (WEE) & Eastern (EEE) Equine Encephalomyelitis – are neurological diseases that affect both horses and people and are commonly known as sleeping sickness. These diseases are transmitted by mosquitos and other blood-sucking insects and are not contagious between horses and humans. Several cases of EEE/WEE are reported annually in the South. EEE is 90% fatal, and WEE is 50% fatal. Clinical signs include fever, depression, recumbence, seizures, mental dullness and death. Influenza (Flu) – is one of the most common respiratory diseases. It is highly contagious between horses and is transmitted via respiratory secretions. Clinical signs include fever, depression, nasal discharge and coughing. Rabies – is a rare but 100% fatal disease in horses. People are often exposed to the infected horse before the disease can be diagnosed and, therefore, create a serious public health concern. Suggested Equine Vaccination Schedule Pregnant Mares – Rhino is given at 3, 5 and 7 months of gestation. A full set of vaccinations (Flu, EEE/WEE, Tetanus, WNV, Rhino, & Rabies) should be given at 10 months of gestation to ensure transfer of antibodies to the foal. Foals – Foals born to mares that were vaccinated in the 10th month of gestation will require EEE/WEE, WNV, Tetanus and Rhino/Flu at 6, 7 and 8 months of age with the addition of rabies at 8 months. Foals born to mares that were NOT vaccinated in the 10th month of gestation will receive the same treatment except at 4, 5 and 6 months of age with the addition of rabies at 6 months. All foals should be revaccinated for all vaccines at 1 year. Yearlings and older – EEE/WEE, Tetanus, Flu, Rhino, Strangles, WNV and Rabies should be given yearly; booster Flu/Rhino and WNV every 6 months. Horses that travel or have high exposure to unfamiliar horses should be boostered with Flu/Rhino every 4 months.