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Tips on Preventing Eastern Equine Encephalitis (EEE) in Your Horse

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With summer in full swing you may think that the summer is winding down, but did you know that August is also peak season for mosquitoes?

With the exceptionally rainy summer that most of the country has experienced, the mosquito population is booming. Not only are mosquitoes an annoyance, they can spread a number of diseases, such as the West Nile Virus, to your horse. Another one of those mosquito borne diseases is Eastern equine encephalitis (EEE). EEE virus is a disease of wild birds that is transmitted to horses and humans by mosquitoes. The virus is found near wetland habitats along the eastern seaboard from New England to Florida.

What Symptoms Should You Look For?

Clinical EEE symptoms include:

  • Moderate to high fever
  • Depression
  • Lack of appetite
  • Cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing)
  • Behavioral changes (aggression, self-mutilation, or drowsiness)
  • Gait abnormalities
  • Severe central nervous system signs (head-pressing, circling, blindness, and seizures)

It is important to be aware that the course of EEE can be quick, with death occurring two to three days after onset of clinical signs despite intensive care. Fatality rates reach 75-80% among horses. Horses that survive might have long-lasting impairments and neurological problems.

What Should You Do If Your Horse Develops Symptoms?

Suspect horse cases should be reported to your veterinarian as soon as possible. Your veterinarian will diagnose the infection and take blood or tissue samples for confirmation. Euthanasia may be necessary because the disease is fatal in unvaccinated animals.

What Can You do to Prevent Infection?

It is important to start by taking action against the mosquitoes themselves. Here are some tips on how you can limit your horses’ exposure to mosquitoes and help to prevent infection:

  • Vaccinate: It is important that you vaccinate your horse(s) against EEE early in the season, BUT it is not too late to vaccinate now. Horses require two doses of the vaccinations initially, and then boosters at least annually. (TheHorse.com)
  • Eliminate standing water: Birdbaths and water tanks are all high risk mosquito breeding grounds so it is important that to take necessary action to prevent any infestations. Be sure to turn over wheelbarrows when not in use and not allow stagnant water to sit in birdbaths or water tanks for long periods of time. Any containers that are needed for constant use, such as water troughs, should be emptied and flushed at least twice each week in order to remove possible mosquito eggs.
  • Maintain gutters: Be sure to keep rain gutters clean and draining properly.
  • Dispose of unneeded items: Remove items from surrounding property that could collect stagnant water, such as old tires, tin cans, and plastic containers.
  • Use a fly repellent formulated to protect against mosquitoes: We recommend the new versatile Force line of fly sprays for horses. Now you have three powerful options to choose from that are specially formulated to protect against mosquitoes:

1. Pro-Force™ Fly Repellent with rapid knockdown, kill and repellency for up to 14 days.

2. Opti-Force™ Sweat Resistant Fly Spray which provides repellency and quick knockdown for 14-day weather-resistant protection.

3. Nature’s Force™ Natural Fly Repellent which provides organic knockdown and kill with 24 hour control.


For double the protection, try the Opti-Force™ Equine Fly Mask. Not only does the Opti-Force fly mask for horses protect the face and eyes, but it is made with Insect Shield® Repellent Technology to provide built-in, invisible, odorless insect protection to repel mosquitoes.

  • Reduce outdoor exposure: Consider keeping horses in the barn from dusk to dawn, when mosquitoes are most active.

EEE is not contagious between horses. While humans can also be infected, the virus does not pass directly between people and horses. Mosquitoes biting warm-blooded animals are the only route of transmission. Remember, it is never too late to vaccinate your horse (s) against EEE and take the necessary steps to prevent infection.


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Amanda Jumbeck

Amanda Jumbeck

Amanda Jumbeck graduated from William Woods University in 2011 with a BS in Equine Science. She currently works on Manna Pro’s Marketing team and enjoys riding horses during her free time.


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