Vaccinate Your Horses for Eastern Equine Encephalomyelitis



Eastern Equine Encephalitis

Eastern Equine Encephalomyelitis

All the above names indicate the same disease spread by mosquitoes. EEE disease resides in the unaffected wild bird population. A mosquito sucks blood from an infected wild bird and then bites a horse or human. Both horses and humans are considered “dead-end” hosts. They cannot produce enough of the virus to spread to another mosquito and then a horse or human. In short, a horse or human cannot affect another horse or human.

Some horse owners vaccinate regularly. Some vaccinate loosely in regards to a calendar and some choose to not vaccinate at all citing expense or dis-belief that EEE is a real concern. The truth is in the science and history.

EEE is prevalent in Florida. Some years it is more prevalent than others. As rainfall increases, mosquito breeding sites increase therefore mosquito populations increase. The best protection you can afford your horse (s) is to vaccinate at least two times a year. The vaccine effective immune response really doesn’t last 12 months. It is best to coordinate your vaccination through your veterinarian but as an informative guideline, vaccinations should occur in the spring before the “rainy” season to build the immune response and again in the fall to boost the immune response. Mares and foals require special vaccination considerations because of the maternal/acquired immunity between mare and foal.

As no vaccine is 100% effective, there are some additional management items a horse owner can do. Mosquitoes are most active at dawn and dusk. Targeting those times for additional protection is advised. I have borrow the below listed items from the UF/IFAS Large Animal Hospital College of Veterinary Medicine. The full article can be viewed at:

What can I do to prevent EEE?

  • Large fan in barn
    Fan moving air through barn
    Vaccinate your horses for EEE at least twice yearly. This is BY FAR the most important step you can take to prevent this fatal disease. Vaccination of foals begins at 6 months of age if their dams have been vaccinated, or 3 months if they have not. Your veterinarian is your best resource for detailed information on correct vaccination schedules for your area.
  • Remove sources of standing water in pastures on your property.
  • Apply fly masks, fly sheets and/or fly leggings to horses when they are at pasture.
  • Spray horses with insect repellent. Regular fly sprays work but only for a few minutes. Longer-acting oil-based repellents are available through your feed store or veterinarian.
  • Keep horses inside during the hours around dawn and dusk. These are the peak feeding times for mosquitoes.
  • Turn fans on in barns for stalled animals or open barn windows to create a breeze. The more powerful the fan, the better the protection.
  • Don’t forget to protect yourself by using insect repellent or wearing protective clothing.


Vaccinating your horse(s) every 6 months in advance of the mosquito season followed by an immune system booster 6 months later is by far the best management you can give to protect them. It is very easy to fall behind the 6 month and 12 month calendar marks for vaccinating your horses. This generally is the case when someone claims to have vaccinated their horse and it develops EEE. For example, vaccinating several months after the 6 month calendar booster has left the horse vulnerable and just because you vaccinated today, it still takes time for the immune response to build. Work with your veterinarian for the best schedule for your geographic area and remember VACCINATE!


Posted: June 25, 2018

Category: Farm Management, Livestock, Pests & Disease
Tags: Eastern, EEE, Encephalitis, Mosquitoes, Vaccinate

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