Equine Vaccines

Equine Vaccines

The specific immunizations needed by a particular horse depend upon several factors: environment, age, breed, sex, use, exposure risk, geographic location and general management. We can help determine the vaccination program best suited to your horse’s individual needs.

Encephalomyelitis: More commonly known as “sleeping sickness”. In Michigan, we vaccinate against Eastern Equine Encephalomyelitis (EEE) and Western Equine Encephalomyelitis (WEE). Sleeping sickness is most often transmitted by mosquitoes, after the insects have acquired the virus from birds and rodents. Signs vary, but include fever, depression, and appetite loss. Later, a horse may stagger when it walks, developing paralysis often leading to death. All horses need an annual vaccine.

West Nile: A virus that is transmitted by mosquitoes that can cause inflammation of the brain and spinal cord (encephalomyelitis). Various species of birds can serve as hosts of the virus. Signs can vary in range and severity, those most frequently seen include incoordination or ataxia, twitching of the muzzle and lower lip, twitching of muscles in neck, shoulders or pectoral region. Signs can be bilateral or unilateral. Other signs can include fever, weakness. The severity of clinical signs depend largely on the area of the central nervous system affected by the virus . Incidence of disease is greater in older horses. All horses need an annual vaccine.

Tetanus: Sometimes called “lockjaw”, it is caused by a toxin producing bacteria that can be found in the intestinal tract of many animals and found in abundance in the soil where horses live. Its spores can exist for years. They enter the body through wounds, lacerations, or the umbilicus of new foals. Clinical signs include muscle stiffness and rigidity, flared nostrils, hypersensitivity and the legs stiffly held in a sawhorse stance. As the disease progresses, muscles in the jaw and face stiffen, preventing the animal from eating or drinking. All horses need an annual vaccination and booster when break in skin occurs.

Influenza: This is a highly contagious respiratory disease. The virus can be transmitted by aerosol from horse to horse over 30 yards. Signs to watch for include fever, depression, loss of appetite, nasal discharge and cough. Influenza viruses are constantly changing or “mutating” and can bypass the horses’ immune defense. Duration of protection is short lived and revaccination may be recommended frequently. Horses that travel , horses at boarding stables, horses that attend equine events and young horses three and younger are most at risk and should be regularly immunized.

Rhinopneumonitis: Two viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) cause two different diseases. Both cause respiratory tract problems, and EHV-1 may also cause abortion, foal death and neurological disease. Infected horses may be feverish and lethargic, may loose appetite and have nasal discharge and cough. The virus is spread by aerosol and by direct contact with secretions, utensils or drinking water. Virus may be present but not apparent in carrier animals. More EHV-1 information can be found at: http://www.aaep.org/info/horse-health?publication=753

Potomac Horse Fever: Potomac is spread by slugs and flying insects that may feed off slugs and then are ingested by a horse. There is not any direct horse to horse transmission of Potomac Horse Fever. Signs include initially off feed, high temperature preceding fluid diarrhea and laminitis.

Rabies: Spread through the saliva of an infected animal, like bats, skunk, raccoon and fox. Rabies is always fatal.

Stangles: Highly contagious bacterial disease caused by the Streptococcus equi found in the soil of affected farms, racetracks and show grounds. Signs include: high temperature, large swollen lymph nodes under the jaw, nasal discharge and cough. Young horses, horses that travel to fairgrounds, boarding stables and come in contact with unknown horses should consider vaccination.

Vaccine Table


Adult horse

Pregnant mares


Annual spring vaccine 6-8 weeks prior to foaling 5 months, 6 months and 1 year of age
West Nile Virus
Annual spring vaccine 6-8 weeks prior to foaling 5 months, 6 months and 1 year of age
Potomac Horse Fever
Every 4 months 3 months, 4 months, then every 4 months
Rabies Annual vaccine 5 months, 6 months and 1 year
Spring and Fall vaccine Influenza 6 -8 weeks prior to foaling 7 months, 8 months, 9 months then every 6 months
Strangles Annual vaccine 5 months, 6 months
Pneumabort-K 3rd, 5th , 7th and 9th month of gestation

Breaking Vaccine News

Already Worse than Last Year

Last year, Michigan experienced the worst outbreak of Eastern Equine Encephalitis (EEE) ever recorded. This year is looking like it will be worse. As of yesterday, 18 cases were confirmed through 8 counties. This is double those reported last year in only 3 counties. Cases have been reported in Barry, Clare, Isabella, Kent, Mecosta, Montcalm, Newaygo, and Oakland.

The Michigan Department of Agriculture and Rural Development highly suggests vaccinating horses, using strong fans in barns from evening and throughout the night when mosquitoes are most active, animal safe insect repellents and eliminating mosquito breeding grounds of standing water where possible.

Signs in horses include fever, difficulty walking or standing, and seizures which eventually lead to death.

Vaccination is the Best Way To Protect Your Horse

Vaccination is the best way to protect your horse because this vaccine is over 95% effective. Un-vaccinated horses, on the other hand, that become infected with EEE, only have a 10% chance of survival.

In People, EEE Causes Long-Term Health Effects

Even if you do not own horses, EEE can still affect you as mosquitoes transmit this disease to both people and horses. Take precautions to protect yourself and others from mosquitoes. In people EEE can cause brain swelling resulting in symptoms ranging from a headache to seizures and even death.

For more information on how to protect yourself and your horses from EEE, please visit the Michigan Department of Agriculture and Rural Development at https://www.michigan.gov/mdard/0,4610,7-125-1572_28248_50968-539057–,00.html

It is not too late! West Nile Virus is in Livingston County. A horse in the Fowlerville area died from it July 21, 2017. Please update your horse’s vaccine if they were last vaccinated over 12 months ago against West Nile Virus.

There have been cases of Eastern Equine Encephalomyelitis (EEE), commonly called sleeping sickness in southern Michigan. If your horse has not been vaccinated in the past 6 months, please be advised a booster is recomended. EEE is a highly fatal mosquito spread neurological disease. Good insect repellants, sheets and fans can aid in protection. EEE is not contagious from horse to horse.

West Nile Virus

Now we have a ten year pattern of disease and response to vaccine. The vaccine has performed very well. The new recommendation is to reduce vaccine from biannual to annual with these exceptions:

  1. Horses shipped to the south for the winter.
  2. Immuno-compromised like horses with Cushings disease and immature horses three years or less.

Potomac Horse Fever Vaccine changes

Potomac Horse Fever was first diagnosed in the late 1970’s. Initially, we vaccinated in the spring and summer because most cases were diagnosed in July and August. With climate change, we see cases as early as May 1st and as late as December 1st. This coupled with the short length of immunity, we now recommend vaccination every four months. Potomac Horse Fever is the most common disease diagnosed in our practice.