The Drill on Equine Encephalitis

Get Rid of Equine Encephalitis Once And For All​

Equine Encephalitis

As the temperature and humidity start to rise, day turn out turns into night turn out. The horses are grazing peacefully out in their wide-open pasture. All is calm before a tiny buzz zips by your ear. The rush makes you think back to whether or not you put on fly spray on your horses. You look out to see that they are happily eating makes you ignore your urge to go out there and spray them. What you don’t know is that one tiny buzzing mosquito could affect your life and the life of your best mare or gelding. Cause this tiny buzzing mosquito carries a virus.

The virus, called Equine Encephalitis, is transferred around by infectious mosquitoes. This disease is also referred to as the “Sleeping Sickness.” These mosquitoes feed upon birds that carry encephalitis but do not have any of the clinical symptoms of the virus. There are 3 different variations of the virus based off where the virus is commonly located. The main variation of Equine Encephalitis commonly occurs in the Eastern part of the United States and Canada. It’s given name is Eastern Equine Encephalitis (EEE). The other 2 variations are Western Equine Encephalitis (WEE) and Venezuelan Equine Encephalitis (VEE). WEE ranges from Argentina to Western Canada and the US states west of the Mississippi River. VEE is found in Central and South America but has been reported in Mexico and the US.

“This virus comes with serious risk of fatality of WEE at approximately 50%, VEE death toll variant at 20% to 80%, and EEE having the highest death toll of them all at 90%.”

Prevent Equine Encephalitis

Trouble For Horses (And You)

Once bitten by an infected black-tailed mosquito ( Culiseta melanura) , the virus has an incubation period of 3 to 7 days. during this period the virus is not infectious. It causes severe brain and nervous system inflammation. It is the owner’s responsibility to look for certain progressive clinical signs. These include biphasic fever (usually on day 2 and day 6), stiffness, and changes to behavior. Behavioral changes can look like hypersensitivity to touch, aggression, wandering, and constant chewing.  However, the most important sign of them all is head pressing.
If any of these signs are being shown, contact your veterinarian immediately. Your veterinarian can give a proper diagnosis from the signs and a blood test. This allows them to see if there are any antibodies fighting against the virus. Once the horse is given the proper diagnosis of Equine Encephalitis, he or she will give treatment.  Treatments include intravenous fluids (dehydration) and anti-inflammatory medications for the brain swelling. This virus comes with a serious risk of fatality. The death rates are as followed: WEE at approximately 50%, VEE death toll variant at 20% to 80%, and EEE has the highest death toll of them all at 90%.
Humans and other animals like mammals, birds, reptiles, and amphibians are also susceptible to the virus. One bite of an infected mosquito and humans start to develop onset symptoms. These symptoms can include fever, headache, and body aches but often go untreated. This leads to the development of more serious symptoms like disorientation, seizures, paralysis. Severe cases have resulted in brain damage caused by brain inflammation, coma, and death. As in infected horses, there is no cure for Equine Encephalitis in humans and other animals, only treatment with fluids and anti-inflammatories.

Solutions To Prevent 

To reduce the chances of your horse receiving any variation of the Equine Encephalitis virus, follow precautions for mosquito control:

  •     Eliminate mosquito breeding grounds – which can occur in any source of water that sits for more than 4 days
  •     Reduce exposure to mosquitoes with insect/mosquito repellent
  •     Avoid turnout for horses during dawn and dusk hours when mosquitoes are biting
  •     Turn on fans or open windows in the barn with stalled horses to create a breeze

Most of all, vaccinate your horse annually to help prevent it from receiving this dangerous virus. Zoetis™ has a vaccine that protects your horse from 5 fatal viruses: EEE, WEE, Rabies, Tetanus, and West Nile. This vaccine is only from your horse’s veterinarian.

Equine Encephalitis

Please consult your veterinarian before diagnosing and treating your horse’s

Neurological Sequelae Resulting from Encephalitic 
Alphavirus Infection – Scientific Figure on ResearchGate. Available from:
[accessed Jul, 2019]

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